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1
Wexler, Hannah M., Elizabeth Tenorio i Lilian Pumbwe. "Characteristics of Bacteroides fragilis lacking the major outer membrane protein, OmpA". Microbiology 155, nr 8 (1.08.2009): 2694–706. http://dx.doi.org/10.1099/mic.0.025858-0.
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OmpA1 is the major outer membrane protein of the Gram-negative anaerobic pathogen Bacteroides fragilis. We identified three additional conserved ompA homologues (ompA2–ompA4) and three less homologous ompA-like genes (ompAs 5, 6 and 7) in B. fragilis. We constructed an ompA1 disruption mutant in B. fragilis 638R (WAL6 ΩompA1) using insertion-mediated mutagenesis. WAL6 ΩompA1 formed much smaller colonies and had smaller, rounder forms on Gram stain analysis than the parental strain or other unrelated disruption mutants. SDS-PAGE and Western blot analysis (with anti-OmpA1 IgY) of the OMP patterns of WAL6 ΩompA1 grown in both high- and low-salt media did not reveal any other OmpA proteins even under osmotic stress. An ompA1 deletant (WAL186ΔompA1) was constructed using a two-step double-crossover technique, and an ompA ‘reinsertant’, WAL360+ompA1, was constructed by reinserting the ompA gene into WAL186ΔompA1. WAL186ΔompA1 was significantly more sensitive to exposure to SDS, high salt and oxygen than the parental (WAL108) or reinsertant (WAL360+ompA1) strain. No significant change was seen in MICs of a variety of antimicrobials for either WAL6 ΩompA1 or WAL186ΔompA1 compared to WAL108. RT-PCR revealed that all of the ompA genes are transcribed in the parental strain and in the disruption mutant, but, as expected, ompA1 is not transcribed in WAL186ΔompA1. Unexpectedly, ompA4 is also not transcribed in WAL186ΔompA1. A predicted structure indicated that among the four OmpA homologues, the barrel portion is more conserved than the loops, except for specific conserved patches on loop 1 and loop 3. The presence of multiple copies of such similar genes in one organism would suggest a critical role for this protein in B. fragilis.
2
Puig, Marta, Carme Fusté i Miquel Viñas. "Outer membrane proteins from Serratia marcescens". Canadian Journal of Microbiology 39, nr 1 (1.01.1993): 108–11. http://dx.doi.org/10.1139/m93-015.
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The outer membrane proteins (OMPs) of several strains of Serratia marcescens have been studied by sodium dodecyl sulphate – urea – polyacrylamide gel electrophoresis. Four major OMPs, named Omp1, Omp2, Omp3, and OmpA (42, 40, 39, and 37 kDa, respectively), have been visualized. The relative proportions of Omp2 and Omp3 depend on cultural conditions (temperature of incubation, osmolarity, and nutrient availability).Key words: Serratia marcescens, outer membrane proteins, porin.
3
Roy Chowdhury, Atish, Shivjee Sah, Umesh Varshney i Dipshikha Chakravortty. "Salmonella Typhimurium outer membrane protein A (OmpA) renders protection from nitrosative stress of macrophages by maintaining the stability of bacterial outer membrane". PLOS Pathogens 18, nr 8 (15.08.2022): e1010708. http://dx.doi.org/10.1371/journal.ppat.1010708.
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Bacterial porins are highly conserved outer membrane proteins used in the selective transport of charged molecules across the membrane. In addition to their significant contributions to the pathogenesis of Gram-negative bacteria, their role(s) in salmonellosis remains elusive. In this study, we investigated the role of outer membrane protein A (OmpA), one of the major outer membrane porins of Salmonella, in the pathogenesis of Salmonella Typhimurium (STM). Our study revealed that OmpA plays an important role in the intracellular virulence of Salmonella. An ompA deficient strain of Salmonella (STM ΔompA) showed compromised proliferation in macrophages. We found that the SPI-2 encoded virulence factors such as sifA and ssaV are downregulated in STM ΔompA. The poor colocalization of STM ΔompA with LAMP-1 showed that disruption of SCV facilitated its release into the cytosol of macrophages, where it was assaulted by reactive nitrogen intermediates (RNI). The enhanced recruitment of nitrotyrosine on the cytosolic population of STM ΔompAΔsifA and ΔompAΔssaV compared to STM ΔsifA and ΔssaV showed an additional role of OmpA in protecting the bacteria from host nitrosative stress. Further, we showed that the generation of greater redox burst could be responsible for enhanced sensitivity of STM ΔompA to the nitrosative stress. The expression of several other outer membrane porins such as ompC, ompD, and ompF was upregulated in STM ΔompA. We found that in the absence of ompA, the enhanced expression of ompF increased the outer membrane porosity of Salmonella and made it susceptible to in vitro and in vivo nitrosative stress. Our study illustrates a novel mechanism for the strategic utilization of OmpA by Salmonella to protect itself from the nitrosative stress of macrophages.
4
Hounsome, Jonathan D. A., Susan Baillie, Mojtaba Noofeli, Alan Riboldi-Tunnicliffe, Richard J. S. Burchmore, Neil W. Isaacs i Robert L. Davies. "Outer Membrane Protein A of Bovine and Ovine Isolates of Mannheimia haemolytica Is Surface Exposed and Contains Host Species-Specific Epitopes". Infection and Immunity 79, nr 11 (6.09.2011): 4332–41. http://dx.doi.org/10.1128/iai.05469-11.
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ABSTRACTMannheimia haemolyticais the etiological agent of pneumonic pasteurellosis of cattle and sheep; two different OmpA subclasses, OmpA1 and OmpA2, are associated with bovine and ovine isolates, respectively. These proteins differ at the distal ends of four external loops, are involved in adherence, and are likely to play important roles in host adaptation.M. haemolyticais surrounded by a polysaccharide capsule, and the degree of OmpA surface exposure is unknown. To investigate surface exposure and immune specificity of OmpA among bovine and ovineM. haemolyticaisolates, recombinant proteins representing the transmembrane domain of OmpA from a bovine serotype A1 isolate (rOmpA1) and an ovine serotype A2 isolate (rOmpA2) were overexpressed, purified, and used to generate anti-rOmpA1 and anti-rOmpA2 antibodies, respectively. Immunogold electron microscopy and immunofluorescence techniques demonstrated that OmpA1 and OmpA2 are surface exposed, and are not masked by the polysaccharide capsule, in a selection ofM. haemolyticaisolates of various serotypes and grown under different growth conditions. To explore epitope specificity, anti-rOmpA1 and anti-rOmpA2 antibodies were cross-absorbed with the heterologous isolate to remove cross-reacting antibodies. These cross-absorbed antibodies were highly specific and recognized only the OmpA protein of the homologous isolate in Western blot assays. A wider examination of the binding specificities of these antibodies forM. haemolyticaisolates representing different OmpA subclasses revealed that cross-absorbed anti-rOmpA1 antibodies recognized OmpA1-type proteins but not OmpA2-type proteins; conversely, cross-absorbed anti-rOmpA2 antibodies recognized OmpA2-type proteins but not OmpA1-type proteins. Our results demonstrate that OmpA1 and OmpA2 are surface exposed and could potentially bind to different receptors in cattle and sheep.
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Scott, Daniel C., Salete M. C. Newton i Phillip E. Klebba. "Surface Loop Motion in FepA". Journal of Bacteriology 184, nr 17 (1.09.2002): 4906–11. http://dx.doi.org/10.1128/jb.184.17.4906-4911.2002.
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ABSTRACT Using a lysine-specific cleavable cross-linking reagent ethylene glycolbis(sulfosuccimidylsuccinate) (Sulfo-EGS), we studied conformational motion in the surface loops of Escherichia coli FepA during its transport of the siderophore ferric enterobactin. Site-directed mutagenesis determined that Sulfo-EGS reacted with two lysines, K332 and K483, and at least two other unidentified Lys residues in the surface loops of the outer membrane protein. The reagent cross-linked K483 in FepA L7 to either K332 in L5, forming a product that we designated band 1, or to the major outer membrane proteins OmpF, OmpC, and OmpA, forming band 2. Ferric enterobactin binding to FepA did not prevent modification of K483 by Sulfo-EGS but blocked its cross-linking to OmpF/C and OmpA and reduced its coupling to K332. These data show that the loops of FepA undergo conformational changes in vivo, with an approximate magnitude of 15 Å, from a ligand-free open state to a ligand-bound closed state. The coupling of FepA L7 to OmpF, OmpC, or OmpA was TonB independent and was unaffected by the uncouplers CCCP (carbonyl cyanide m-chlorophenylhydrazone) and DNP (2,4-dinitrophenol) but completely inhibited by cyanide.
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Subramaniam, Sumathi, Bin Huang, Hilda Loh, Jimmy Kwang, Hai-Meng Tan, Kim-Lee Chua i Joachim Frey. "Characterization of a Predominant Immunogenic Outer Membrane Protein of Riemerella anatipestifer". Clinical Diagnostic Laboratory Immunology 7, nr 2 (1.03.2000): 168–74. http://dx.doi.org/10.1128/cdli.7.2.168-174.2000.
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ABSTRACT The ompA gene, encoding the 42-kDa major antigenic outer membrane protein OmpA of Riemerella anatipestifer, the etiololgical agent of septicemia anserum exsudativa, was cloned and expressed in Escherichia coli. Recombinant OmpA displayed a molecular mass similar to that predicted from the nucleotide sequence of the ompA gene but lower than that observed in total cell lysates of R. anatipestifer. The ompA gene showed a conserved C-terminal region comprising the OmpA-like domain and a variable N-terminal region. This structure is similar to those of the analogous outer membrane proteins of several gram-negative bacteria. However, OmpA of R. anatipestifercontains six EF-hand calcium-binding domains and two PEST regions, which distinguish it from other outer membrane proteins. The occurrence of these motifs in OmpA suggests a possible role in virulence for this protein. The ompA gene is present in the R. anatipestifer type strain and in all serotype reference strains. However, it exhibits some minor genetic heterogeneity among different serotypes, which seems not to affect the strong antigenic characteristics of the protein. OmpA is a conserved and strong antigenic determinant of R. anatipestifer and hence is suggested to be a valuable protein for the serodetection of R. anatipestifer infections, independent of their serotype.
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Charlson, Emily S., John N. Werner i Rajeev Misra. "Differential Effects of yfgL Mutation on Escherichia coli Outer Membrane Proteins and Lipopolysaccharide". Journal of Bacteriology 188, nr 20 (1.10.2006): 7186–94. http://dx.doi.org/10.1128/jb.00571-06.
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ABSTRACT YfgL together with NlpB, YfiO, and YaeT form a protein complex to facilitate the insertion of proteins into the outer membrane of Escherichia coli. Without YfgL, the levels of OmpA, OmpF, and LamB are significantly reduced, while OmpC levels are slightly reduced. In contrast, the level of TolC significantly increases in a yfgL mutant. When cells are depleted of YaeT or YfiO, levels of all outer membrane proteins examined, including OmpC and TolC, are severely reduced. Thus, while the assembly pathways of various nonlipoprotein outer membrane proteins may vary through the step involving YfgL, all assembly pathways in Escherichia coli converge at the step involving the YaeT/YfiO complex. The negative effect of yfgL mutation on outer membrane proteins may in part be due to elevated sigma E activity, which has been shown to downregulate the synthesis of various outer membrane proteins while upregulating the synthesis of periplasmic chaperones, foldases, and lipopolysaccharide. The data presented here suggest that the yfgL effect on outer membrane proteins also stems from a defective assembly apparatus, leading to aberrant outer membrane protein assembly, except for TolC, which assembles independent of YfgL. Consistent with this view, the simultaneous absence of YfgL and the major periplasmic protease DegP confers a synthetic lethal phenotype, presumably due to the toxic accumulation of unfolded outer membrane proteins. The results support the hypothesis that TolC and major outer membrane proteins compete for the YaeT/YfiO complex, since mutations that adversely affect synthesis or assembly of major outer membrane proteins lead to elevated TolC levels.
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Oh, Kyu-Wan, Kyeongmin Kim, Md Maidul Islam, Hye-Won Jung, Daejin Lim, Je Chul Lee i Minsang Shin. "Transcriptional Regulation of the Outer Membrane Protein A in Acinetobacter baumannii". Microorganisms 8, nr 5 (11.05.2020): 706. http://dx.doi.org/10.3390/microorganisms8050706.
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Acinetobacter baumannii is known for its virulence in severely ill, hospitalized patients and for exhibiting multidrug resistance. A. baumannii infection treatment poses a serious problem in clinical environments. The outer membrane protein A (OmpA) of the Acinetobacter genus is involved in bacterial virulence. Regulatory factors of OmpA in the post-transcriptional stage have been previously identified. However, the regulatory factors that act before the transcriptional stage remain unclear. We investigated the A1S_0316 gene that encodes a putative transcription factor for OmpA expression in A. baumannii. A1S_0316 was purified and examined using size-exclusion chromatography, which revealed that it forms an oligomer. The binding affinity of A1S_0316 to the OmpA promoter region was also examined. We compared the binding affinity to the OmpA promotor region between A1S_0316 and the AbH-NS protein. A1S_0316 showed higher binding affinity to the OmpA promotor region than did H-NS. We examined the regulatory effect of these proteins on OmpA expression in A. baumannii using real-time qPCR and various in vitro tools. Our results indicated that A1S_0316 acts as an anti-repressor on the promotor region of the OmpA gene by inhibiting the binding of the AbH-NS protein. This study was the first demonstration of the transcriptional regulation of OmpA expression.
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Pai, Suresh R., Yvonne Upshaw i Shiva P. Singh. "Characterization of monoclonal antibodies to the outer membrane protein (OmpD) of Salmonella typhimurium". Canadian Journal of Microbiology 38, nr 11 (1.11.1992): 1102–7. http://dx.doi.org/10.1139/m92-181.
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A panel of monoclonal antibodies, seven against the trimeric and seven against the monomeric forms to outer membrane protein D (OmpD) of Salmonella typhimurium were produced. The specificities of these monoclonal antibodies for the porin proteins of S. typhimurium and their cross-reactions with Salmonella porins OmpC and OmpF were determined by Western immunoblotting and enzyme-linked immunosorbent assay. We observed that OmpD shared more epitopes and had greater structural similarity with OmpC than with OmpF. Key words: Salmonella typhimurium, outer membrane protein, monoclonal antibody, trimeric, monomeric.
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Singh, Pushpendra, Manish Kumar Tripathi, Mohammad Yasir, Ashish Ranjan i Rahul Shrivastava. "Effects of carbamate pesticides intermediates on Escherichia coli membrane architecture: An in vitro and in silico approach". Environmental Analysis Health and Toxicology 36, nr 3 (25.08.2021): e2021020. http://dx.doi.org/10.5620/eaht.2021020.
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Methyl isocyanate (MIC), a low molecular weight synthetic aliphatic compound, having an isocyanate group (−NCO), has industrial application. In this study, the effects of methyl isocyanate and its mechanism on outer membrane protein of Escherichia coli were observed using experimental and computational methods. In vitro exposure of N-succinimidyl N-methylcarbamate (NSNM) a synthetic analogue of MIC on E. coli to a final concentration of 2 mM was found to affect the growth curve pattern and changes in cell morphology. Molecular docking studies of MIC and NSNM with E. coli outer membrane protein (OmpW, OmpX, OmpF OmpA), and periplasmic domain (PAL) were performed. The in-silico results revealed that outer membrane protein OmpF showed the highest negative binding energy, i.e. ∆G -4.11 kcal/mole and ∆G -3.19 kcal/mole by NSNM and MIC as compared to other proteins. Our study concludes that methyl isocyanate retains lethal toxicity which leads to cell death due to the membrane protein damage of E. coli membrane.
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Koebnik, Ralf. "Structural and Functional Roles of the Surface-Exposed Loops of the β-Barrel Membrane Protein OmpA fromEscherichia coli". Journal of Bacteriology 181, nr 12 (15.06.1999): 3688–94. http://dx.doi.org/10.1128/jb.181.12.3688-3694.1999.
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ABSTRACT The N-terminal domain of the OmpA protein from Escherichia coli, consisting of 170 amino acid residues, is embedded in the outer membrane, in the form of an antiparallel β-barrel whose eight transmembrane β-strands are connected by three short periplasmic turns and four relatively large surface-exposed hydrophilic loops. This protein domain serves as a paradigm for the study of membrane assembly of integral β-structured membrane proteins. In order to dissect the structural and functional roles of the surface-exposed loops, they were shortened separately and in all possible combinations. All 16 loop deletion mutants assembled into the outer membrane with high efficiency and adopted the wild-type membrane topology. This systematic approach proves the absence of topogenic signals (e.g., in the form of loop sizes or charge distributions) in these loops. The shortening of surface-exposed loops did not reduce the thermal stability of the protein. However, none of the mutant proteins, with the exception of the variant with the fourth loop shortened, served as a receptor for the OmpA-specific bacteriophage K3. Furthermore, all loops were necessary for the OmpA protein to function in the stabilization of mating aggregates during F conjugation. An OmpA deletion variant with all four loops shortened, consisting of only 135 amino acid residues, constitutes the smallest β-structured integral membrane protein known to date. These results represent a further step toward the development of artificial outer membrane proteins.
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Prasadarao, Nemani V. "Identification of Escherichia coli Outer Membrane Protein A Receptor on Human Brain Microvascular Endothelial Cells". Infection and Immunity 70, nr 8 (sierpień 2002): 4556–63. http://dx.doi.org/10.1128/iai.70.8.4556-4563.2002.
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ABSTRACT Neonatal Escherichia coli meningitis continues to be a diagnostic and treatment challenge despite the availability of active antibiotics. Our earlier studies have shown that outer membrane protein A (OmpA) is one of the major factors responsible for Escherichia coli traversal across the blood-brain barrier that constitutes a lining of brain microvascular endothelial cells (BMEC). In this study we showed that OmpA binds to a 95-kDa human BMEC (HBMEC) glycoprotein (Ecgp) for E. coli invasion. Ecgp was partially purified by wheat germ agglutinin and Maackia amurensis lectin (MAL) affinity chromatography. The MAL affinity-purified HBMEC proteins bound to OmpA+ E. coli but not to OmpA− E. coli. In addition, the deglycosylated MAL-bound proteins still interact with OmpA+ E. coli, indicating the role of protein backbone in mediating the OmpA binding to HBMEC. Interestingly, the MAL affinity-bound fraction showed one more protein, a 65-kDa protein that bound to OmpA+ E. coli in addition to Ecgp. Further, the 65-kDa protein was shown to be a cleavage product of Ecgp. Immunocytochemistry of HBMEC infected with OmpA+ E. coli by using anti-Ecgp antibody suggests that Ecgp clusters at the E. coli entry site. Anti-Ecgp antibody also reacted to microvascular endothelium on human brain tissue sections, indicating the biological relevance of Ecgp in E. coli meningitis. Partial N-terminal amino acid sequence of Ecgp suggested that it has 87% sequence homology to gp96, an endoplasmic reticulum-resident molecular chaperone that is often expressed on the cell surface. In contrast, the 65-kDa protein, which could be the internal portion of Ecgp, showed 70% sequence homology to an S-fimbria-binding sialoglycoprotein reported earlier. These results suggest that OmpA interacts with Ecgp via the carbohydrate epitope, as well as with the protein portion for invading HBMEC.
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Zhou, Gang, Qian Wang, Yingsi Wang, Xia Wen, Hong Peng, Ruqun Peng, Qingshan Shi, Xiaobao Xie i Liangqiu Li. "Outer Membrane Porins Contribute to Antimicrobial Resistance in Gram-Negative Bacteria". Microorganisms 11, nr 7 (28.06.2023): 1690. http://dx.doi.org/10.3390/microorganisms11071690.
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Gram-negative bacteria depend on their cell membranes for survival and environmental adaptation. They contain two membranes, one of which is the outer membrane (OM), which is home to several different outer membrane proteins (Omps). One class of important Omps is porins, which mediate the inflow of nutrients and several antimicrobial drugs. The microorganism’s sensitivity to antibiotics, which are predominantly targeted at internal sites, is greatly influenced by the permeability characteristics of porins. In this review, the properties and interactions of five common porins, OmpA, OmpC, OmpF, OmpW, and OmpX, in connection to porin-mediated permeability are outlined. Meanwhile, this review also highlighted the discovered regulatory characteristics and identified molecular mechanisms in antibiotic penetration through porins. Taken together, uncovering porins’ functional properties will pave the way to investigate effective agents or approaches that use porins as targets to get rid of resistant gram-negative bacteria.
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Enfedaque, Josefina, Santiago Ferrer, Joan Francesc Guasch, Miguel Regué i Joan Tomás. "Bacteriocin 28b fromSerratia marcescensN28b: identification ofEscherichia colisurface components involved in bacteriocin binding and translocation". Canadian Journal of Microbiology 42, nr 1 (1.01.1996): 19–26. http://dx.doi.org/10.1139/m96-004.
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Serratia marcescens N28b produces bacteriocin 28b, active against Escherichia coli. Bacteriocin sensitivity tests performed on a collection of E. coli envelope mutants, and isolation and characterization of E. coli bacteriocin-28b-insensitive mutants, showed that the core lipopolysaccharide, outer membrane proteins OmpA and OmpF, and TolQ, TolA, and TolB proteins are involved in bacteriocin 28b lethal activity. These mutants were assayed for bacteriocin 28b sensitivity under normal and bypass conditions, and their bacteriocin-binding ability was determined. The results obtained suggest that the core lipopolysaccaride and outer membrane proteins OmpA and OmpF are involved in bacteriocin 28b binding. Furthermore, bacteriocin 28b translocation requires proteins TolA, TolB, and TolQ.Key words: bacteriocin, receptors, translocation, Serratia marcescens.
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Torres, Alfredo G., Yongguo Li, Christopher B. Tutt, Lijun Xin, Tonyia Eaves-Pyles i Lynn Soong. "Outer Membrane Protein A of Escherichia coli O157:H7 Stimulates Dendritic Cell Activation". Infection and Immunity 74, nr 5 (maj 2006): 2676–85. http://dx.doi.org/10.1128/iai.74.5.2676-2685.2006.
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ABSTRACT Outer membrane protein A (OmpA) is located in the membrane of Escherichia coli and other gram-negative bacteria and plays a multifunctional role in bacterial physiology and pathogenesis. In enterohemorrhagic E. coli (EHEC), especially serotype O157:H7, OmpA interacts with cultured human intestinal cells and likely acts as an important component to stimulate the immune response during infection. To test this hypothesis, we analyzed the effect of EHEC OmpA on cytokine production by dendritic cells (DCs) and on DC migration across polarized intestinal epithelial cells. OmpA induced murine DCs to secrete interleukin-1 (IL-1), IL-10, and IL-12 in a dose-dependent manner, and this effect was independent of Toll-like receptor 4. Although DCs displayed differential responses to EHEC OmpA and OmpA-specific antibodies enhanced DC cytokine secretion, we cannot discard that other EHEC surface elements were likely to be involved. While OmpA was required for bacterial binding to polarized Caco-2 cells, it was not needed for the induction of cytokine production by Caco-2 cells or for human DC migration across polarized cells.
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Hellman, Judith, Paul M. Loiselle, Megan M. Tehan, Jennifer E. Allaire, Lenora A. Boyle, James T. Kurnick, David M. Andrews, Kwang Sik Kim i H. Shaw Warren. "Outer Membrane Protein A, Peptidoglycan-Associated Lipoprotein, and Murein Lipoprotein Are Released by Escherichia coli Bacteria into Serum". Infection and Immunity 68, nr 5 (1.05.2000): 2566–72. http://dx.doi.org/10.1128/iai.68.5.2566-2572.2000.
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ABSTRACT Complexes containing lipopolysaccharide (LPS) and three outer membrane proteins (OMPs) are released by gram-negative bacteria incubated in human serum and into the circulation in an experimental model of sepsis. The same OMPs are bound by immunoglobulin G (IgG) in the cross-protective antiserum raised to Escherichia coliJ5 (anti-J5 IgG). This study was performed to identify the three OMPs. The 35-kDa OMP was identified as outer membrane protein A (OmpA) by immunoblotting studies using OmpA-deficient bacteria and recombinant OmpA protein. The 18-kDa OMP was identified as peptidoglycan-associated lipoprotein (PAL) based on peptide sequences from the purified protein and immunoblotting studies using PAL-deficient bacteria. The 5- to 9-kDa OMP was identified as murein lipoprotein (MLP) based on immunoblotting studies using MLP-deficient bacteria. The studies identify the OMPs released into human serum and into the circulation in an experimental model of sepsis as OmpA, PAL, and MLP.
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Chen, Chen, Nana Wu, Na Rong, Chao Kang, Chunlin Chen, Sanqiao Wu, Xiang Liu i Xiaoying Zhang. "Immunoprotective evaluation of Escherichia coli outer membrane protein A against the main pathogens of animal mastitis". Tropical Journal of Pharmaceutical Research 19, nr 1 (9.04.2020): 155–62. http://dx.doi.org/10.4314/tjpr.v19i1.23.
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Purpose: To evaluate prokaryotic expression of the Escherichia coli (E. coli) outer membrane protein A (OmpA) and its immunoprotective function against the main pathogens of animal mastitis.Methods: A molecular cloning method was used to develop a prokaryotic strain expressing OmpA protein, which was purified by Ni-affinity chromatography. Polyclonal antiserum was generated in mice immunized with OmpA protein. Enzyme-linked immunosorbent assay (ELISA) and western blotting were used to determine the titer and verify anti-OmpA serum specificity, respectively. Interaction between OmpA antiserum and main pathogens of animal mastitis was verified by ELISA and a pull-down method. The immune protective function of OmpA protein was evaluated in mice challenged with pathogens of animal mastitis. Optimal fermentation conditions to produce OmpA protein were determined by the L9(34) orthogonal test.Results: A prokaryotic strain expressing OmpA protein was developed, and purified OmpA was used to develop a mouse polyclonal antibody. The anti-OmpA serum exhibited high specificity and a titer of 1:1600. Anti-OmpA serum directly interacted with E. coli and Staphylococcus aureus (S. aureus). OmpA demonstrated a significant immune protective function of 58.33 % against E. coli and 46.15 % against S. aureus. The optimal conditions for expressing fermentation OmpA were a strain absorbance of 0.5 at a wavelength of 600 nm, IPTG final concentration of 0.3 mmol/L, induction time of 12 h, and induction temperature of 28 °C.Conclusion: OmpA possesses selective immunogenicity and a significant immune protective effect against the main pathogens of animal mastitis. The results suggest that OmpA may potentially be used as a vaccine for animal mastitis.
Keywords: E. coli, OmpA protein, Immunoprotection, Animal mastitis, Protein fermentation
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Zhang, J. J., M. Hamachi, T. Hamachi, Y. P. Zhao i D. T. Yu. "The bacterial outer membrane protein that reacts with anti-HLA-B27 antibodies is the OmpA protein." Journal of Immunology 143, nr 9 (1.11.1989): 2955–60. http://dx.doi.org/10.4049/jimmunol.143.9.2955.
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Abstract A bacterial outer membrane protein of 35-kDa Mr has been reported to react with several anti-HLA-B27 mAb. Here, we demonstrated that this protein showed the heat-modifiability of the OmpA protein during SDS-PAGE. Further, the protein was not detected in mutants of Escherichia coli in which the expression of the OmpA protein has been suppressed. The protein would be reexpressed when one of the mutants was transformed with an expression vector carrying the OmpA gene. Finally, the identity of the reactive protein to OmpA protein was verified by homology in amino acid sequences. An NH2-terminal fragment of this protein was generated by tryptic digestion. Inasmuch as this was unreactive with the anti-HLA-B27 antibody, we concluded that the carboxyl-terminus contributed directly or indirectly to the reactive domain.
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Power, Michelle L., Belinda C. Ferrari, Jane Littlefield-Wyer, David M. Gordon, Martin B. Slade i Duncan A. Veal. "A Naturally Occurring Novel Allele of Escherichia coli Outer Membrane Protein A Reduces Sensitivity to Bacteriophage". Applied and Environmental Microbiology 72, nr 12 (15.09.2006): 7930–32. http://dx.doi.org/10.1128/aem.01040-06.
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ABSTRACT A novel Escherichia coli outer membrane protein A (OmpA) was discovered through a proteomic investigation of cell surface proteins. DNA polymorphisms were localized to regions encoding the protein's surface-exposed loops which are known phage receptor sites. Bacteriophage sensitivity testing indicated an association between bacteriophage resistance and isolates having the novel ompA allele.
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Santiviago, Carlos A., Cecilia S. Toro, Alejandro A. Hidalgo, Philip Youderian i Guido C. Mora. "Global Regulation of the Salmonella enterica Serovar Typhimurium Major Porin, OmpD". Journal of Bacteriology 185, nr 19 (1.10.2003): 5901–5. http://dx.doi.org/10.1128/jb.185.19.5901-5905.2003.
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ABSTRACT The OmpD porin is the most abundant outer membrane protein in Salmonella enterica serovar Typhimurium and represents about 1% of total cell protein. Unlike the case with the less abundant OmpC and OmpF porins, the stoichiometry of OmpD in the outer membrane does not change in response to changes in osmolarity. The abundance of OmpD increases in response to anaerobiosis and decreases in response to low pH, conditions encountered by serovar Typhimurium during the infection of its murine host. By constructing an operon fusion of the lacZY genes with the ompD promoter, we show that the abundance of OmpD in the outer membrane is regulated primarily at the level of transcription and is subject to catabolite repression. In response to anaerobiosis, the abundance of OmpD in the outer membrane also appears to be controlled posttranscriptionally by a function dependent on Fnr.
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Ojogun, Nore, Amandeep Kahlon, Stephanie A. Ragland, Matthew J. Troese, Juliana E. Mastronunzio, Naomi J. Walker, Lauren VieBrock i in. "Anaplasma phagocytophilum Outer Membrane Protein A Interacts with Sialylated Glycoproteins To Promote Infection of Mammalian Host Cells". Infection and Immunity 80, nr 11 (20.08.2012): 3748–60. http://dx.doi.org/10.1128/iai.00654-12.
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ABSTRACTAnaplasma phagocytophilumis the tick-transmitted obligate intracellular bacterium that causes human granulocytic anaplasmosis (HGA).A. phagocytophilumbinding to sialyl Lewis x (sLex) and other sialylated glycans that decorate P selectin glycoprotein 1 (PSGL-1) and other glycoproteins is critical for infection of mammalian host cells. Here, we demonstrate the importance ofA. phagocytophilumouter membrane protein A (OmpA) APH_0338 in infection of mammalian host cells. OmpA is transcriptionally induced during transmission feeding ofA. phagocytophilum-infected ticks on mice and is upregulated during invasion of HL-60 cells. OmpA is presented on the pathogen's surface. Sera from HGA patients and experimentally infected mice recognize recombinant OmpA. Pretreatment ofA. phagocytophilumorganisms with OmpA antiserum reduces their abilities to infect HL-60 cells. The OmpA N-terminal region is predicted to contain the protein's extracellular domain. GlutathioneS-transferase (GST)-tagged versions of OmpA and OmpA amino acids 19 to 74 (OmpA19-74) but not OmpA75-205bind to, and competitively inhibitA. phagocytophiluminfection of, host cells. Pretreatment of host cells with sialidase or trypsin reduces or nearly eliminates, respectively, GST-OmpA adhesion. Therefore, OmpA interacts with sialylated glycoproteins. This study identifies the firstA. phagocytophilumadhesin-receptor pair and delineates the region of OmpA that is critical for infection.
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Skerniškytė, Jūratė, Emilija Karazijaitė, Asta Lučiūnaitė i Edita Sužiedėlienė. "OmpA Protein-Deficient Acinetobacter baumannii Outer Membrane Vesicles Trigger Reduced Inflammatory Response". Pathogens 10, nr 4 (31.03.2021): 407. http://dx.doi.org/10.3390/pathogens10040407.
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Multidrug resistant Acinetobacter baumannii shows a growing number of nosocomial infections worldwide during the last decade. The outer membrane vesicles (OMVs) produced by this bacterium draw increasing attention as a possible treatment target. OMVs have been implicated in the reduction of antibiotic level in the surrounding environment, transfer of virulence factors into the host cells, and induction of inflammatory response. Although the evidence on the involvement of OMVs in A. baumannii pathogenesis is currently growing, their role during inflammation is insufficiently explored. It is likely that bacteria, by secreting OMVs, can expand the area of their exposure and prepare surrounding matrix for infection. Here, we investigated the impact of A. baumannii OMVs on activation of macrophages in vitro. We show that OmpA protein present in A. baumannii OMVs substantially contributes to the proinflammatory response in J774 murine macrophages and to the cell death in both lung epithelium cells and macrophages. The loss of OmpA protein in OMVs, obtained from A. baumannii ∆ompA mutant, resulted in the altered expression of genes coding for IL-6, NLRP3 and IL-1β proinflammatory molecules in macrophages in vitro. These results imply that OmpA protein in bacterial OMVs could trigger a more intense proinflammatory response.
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Klose, M., A. Störiko, Y. D. Stierhof, I. Hindennach, B. Mutschler i U. Henning. "Membrane assembly of the outer membrane protein OmpA of Escherichia coli." Journal of Biological Chemistry 268, nr 34 (grudzień 1993): 25664–70. http://dx.doi.org/10.1016/s0021-9258(19)74441-x.
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White, Peter A., Sean P. Nair, Mi-Jurng Kim, Michael Wilson i Brian Henderson. "Molecular Characterization of an Outer Membrane Protein ofActinobacillus actinomycetemcomitans Belonging to the OmpA Family". Infection and Immunity 66, nr 1 (1.01.1998): 369–72. http://dx.doi.org/10.1128/iai.66.1.369-372.1998.
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ABSTRACT The major outer membrane protein (OMP) of Actinobacillus actinomycetemcomitans is an OmpA homolog that demonstrates electrophoretic heat modifiability. The gene encoding this protein was isolated from a genomic library of A. actinomycetemcomitansNCTC 9710 by immunoscreening with serum from a patient with localized juvenile periodontitis. Expression of the cloned gene inEscherichia coli and subsequent Western blot analysis revealed a protein with an approximate molecular mass of 34 kDa. The amino acid sequence predicted from the cloned gene demonstrated that the mature protein had a molecular mass of 34,911 Da and significant identity to members of the OmpA family of proteins. We have named the major OMP of A. actinomycetemcomitans Omp34, and its corresponding gene has been named omp34.
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Queiroz, Paula A., Jean E. Meneguello, Bruna R. Silva, Katiany R. Caleffi-Ferracioli, Regiane BL Scodro, Rosilene F. Cardoso, Rogério Marchiosi i Vera LD Siqueira. "Proteomic profiling of Klebsiella pneumoniae carbapenemase (KPC)-producer Klebsiella pneumoniae after induced polymyxin resistance". Future Microbiology 16, nr 15 (październik 2021): 1195–207. http://dx.doi.org/10.2217/fmb-2021-0005.
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Aim: To elucidate the changes in protein expression associated with polymyxin resistance in Klebsiella pneumoniae, we profiled a comparative proteomic analysis of polymyxin B-resistant mutants KPC-2-producing K. pneumoniae, and of its susceptible counterparts. Material & methods: Two-dimensional reversed phase nano ultra-performance liquid chromatography mass spectrometry was used for proteomic analysis. Results: Our results showed that the proteomic profile involved several biological processes, and we highlight the downregulation of outer membrane protein A (OmpA) and the upregulation of SlyB outer membrane lipoprotein (conserved protein member of the PhoPQ regulon) and AcrA multidrug efflux pump in polymyxin B-resistant strains. Conclusion: Our results highlight the possible participation of the SlyB, AcrA and OmpA proteins in the determination of polymyxin B heteroresistance in KPC-2-producing K. pneumoniae.
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Ried, G., I. Hindennach i U. Henning. "Role of lipopolysaccharide in assembly of Escherichia coli outer membrane proteins OmpA, OmpC, and OmpF." Journal of Bacteriology 172, nr 10 (1990): 6048–53. http://dx.doi.org/10.1128/jb.172.10.6048-6053.1990.
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Barel, Gilli, Alexandra Sirota, Hanne Volpin i Edouard Jurkevitch. "Fate of Predator and Prey Proteins during Growth of Bdellovibrio bacteriovorus on Escherichia coli and Pseudomonas syringae Prey". Journal of Bacteriology 187, nr 1 (1.01.2005): 329–35. http://dx.doi.org/10.1128/jb.187.1.329-335.2005.
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ABSTRACT A two-dimensional electrophoretic analysis of protein distribution followed by identification of selected proteins by mass spectrometry was performed on fresh bdellovibrio cultures containing attack phase cells of the predatory bacterium Bdellovibrio bacteriovorus strain 109J-1 and the remains of an Escherichia coli or a Pseudomonas syringae pv. tomato prey. Cleavage of the peptidoglycan-associated outer membrane proteins (OMPs) OmpA in E. coli and OprF in P. syringae occurred in both prey. The tryptic peptides obtained from the cleavage products of OmpA and OprF were all located within the 19-kDa pronase-resistant N-terminal parts of the corresponding proteins. The predator cell fraction was separated from the prey ghosts in fresh bdellovibrio cultures by centrifugation on a Percoll-sucrose cushion. Proteins from each fraction were separated by two-dimensional electrophoresis and identified by mass spectrometric analysis. As no prey OMP could be detected in the predator cell fraction, it was concluded that prey OMPs are not transferred to the predator, as had been suggested previously. However, a protein from the predator was found bound to ghost cell envelopes. This protein may correspond to a protein earlier suggested to be associated with the prey outer or cytoplasmic membranes. Along with recently described polypeptides from B. bacteriovorus strains 100 and 114, it forms a new family of putative outer membrane proteins.
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March, Catalina, David Moranta, Verónica Regueiro, Enrique Llobet, Anna Tomás, Junkal Garmendia i José A. Bengoechea. "Klebsiella pneumoniae Outer Membrane Protein A Is Required to Prevent the Activation of Airway Epithelial Cells". Journal of Biological Chemistry 286, nr 12 (28.01.2011): 9956–67. http://dx.doi.org/10.1074/jbc.m110.181008.
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Outer membrane protein A (OmpA) is a class of proteins highly conserved among the Enterobacteriaceae family and throughout evolution. Klebsiella pneumoniae is a capsulated Gram-negative pathogen. It is an important cause of community-acquired and nosocomial pneumonia. Evidence indicates that K. pneumoniae infections are characterized by a lack of an early inflammatory response. Data from our laboratory indicate that K. pneumoniae CPS helps to suppress the host inflammatory response. However, it is unknown whether K. pneumoniae employs additional factors to modulate host inflammatory responses. Here, we report that K. pneumoniae OmpA is important for immune evasion in vitro and in vivo. Infection of A549 and normal human bronchial cells with 52OmpA2, an ompA mutant, increased the levels of IL-8. 52145-ΔwcaK2ompA, which does not express CPS and ompA, induced the highest levels of IL-8. Both mutants could be complemented. In vivo, 52OmpA2 induced higher levels of tnfα, kc, and il6 than the wild type. ompA mutants activated NF-κB, and the phosphorylation of p38, p44/42, and JNK MAPKs and IL-8 induction was via NF-κB-dependent and p38- and p44/42-dependent pathways. 52OmpA2 engaged TLR2 and -4 to activate NF-κB, whereas 52145-ΔwcaK2ompA activated not only TLR2 and TLR4 but also NOD1. Finally, we demonstrate that the ompA mutant is attenuated in the pneumonia mouse model. The results of this study indicate that K. pneumoniae OmpA contributes to attenuate airway cell responses. This may facilitate pathogen survival in the hostile environment of the lung.
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Rolhion, Nathalie, Nicolas Barnich, Laurent Claret i Arlette Darfeuille-Michaud. "Strong Decrease in Invasive Ability and Outer Membrane Vesicle Release in Crohn's Disease-Associated Adherent-Invasive Escherichia coli Strain LF82 with the yfgL Gene Deleted". Journal of Bacteriology 187, nr 7 (1.04.2005): 2286–96. http://dx.doi.org/10.1128/jb.187.7.2286-2296.2005.
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ABSTRACT Adherent-invasive Escherichia coli strain LF82 recovered from a chronic lesion of a patient with Crohn's disease is able to invade cultured intestinal epithelial cells. Three mutants with impaired ability to invade epithelial cells had the Tn5phoA transposon inserted in the yfgL gene encoding the YfgL lipoprotein. A yfgL- negative isogenic mutant showed a marked decrease both in its ability to invade Intestine-407 cells and in the amount of the outer membrane proteins OmpA and OmpC in the culture supernatant, as shown by analysis of the culture supernatant protein contents by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and matrix-assisted laser desorption ionization-time of flight mass spectrometry. Transcomplementation of the LF82-ΔyfgL isogenic mutant with the cloned yfgL gene restored invasion ability and outer membrane protein release in the culture supernatant. The outer membrane proteins in the culture supernatant of strain LF82 resulted from the formation of vesicles. This was shown by Western blot analysis of periplasmic and outer membrane fraction markers typically found in outer membrane vesicles and by transmission electron microscopic analysis of ultracentrifuged cell-free LF82 supernatant pellets, indicating the presence of vesicles with a bilayered structure surrounding a central electron-dense core. Thus, deletion of the yfgL gene in strain LF82 resulted in a decreased ability to invade intestinal epithelial cells and a decreased release of outer membrane vesicles.
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Pornwiroon, Walairat, Apichai Bourchookarn, Christopher D. Paddock i Kevin R. Macaluso. "Proteomic Analysis of Rickettsia parkeri Strain Portsmouth". Infection and Immunity 77, nr 12 (21.09.2009): 5262–71. http://dx.doi.org/10.1128/iai.00911-09.
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ABSTRACT Rickettsia parkeri, a recently recognized pathogen of human, is one of several Rickettsia spp. in the United States that causes a spotted fever rickettsiosis. To gain insights into its biology and pathogenesis, we applied the proteomics approach to establish a two-dimensional gel proteome reference map and combined this technique with cell surface biotinylation to identify surface-exposed proteins of a low-passage isolate of R. parkeri obtained from a patient. We identified 91 proteins by matrix-assisted laser desorption ionization-tandem time of flight mass spectrometry. Of these, 28 were characterized as surface proteins, including virulence-related proteins (e.g., outer membrane protein A [OmpA], OmpB, β-peptide, and RickA). Two-dimensional immunoblotting with serum from the R. parkeri-infected index patient was utilized to identify the immunoreactive proteins as potential targets for diagnosis and vaccine development. In addition to the known rickettsial antigens, OmpA and OmpB, we identified translation initiation factor 2, cell division protein FtsZ, and cysteinyl-tRNA synthetase as immunoreactive proteins. The proteome map with corresponding cell surface protein analysis and antigen detection will facilitate a better understanding of the mechanisms of rickettsial pathogenesis.
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Davies, Robert L., i Inkyoung Lee. "Sequence Diversity and Molecular Evolution of the Heat-Modifiable Outer Membrane Protein Gene (ompA) of Mannheimia(Pasteurella) haemolytica, Mannheimia glucosida, and Pasteurella trehalosi". Journal of Bacteriology 186, nr 17 (1.09.2004): 5741–52. http://dx.doi.org/10.1128/jb.186.17.5741-5752.2004.
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ABSTRACT The OmpA (or heat-modifiable) protein is a major structural component of the outer membranes of gram-negative bacteria. The protein contains eight membrane-traversing β-strands and four surface-exposed loops. The genetic diversity and molecular evolution of OmpA were investigated in 31 Mannheimia (Pasteurella) haemolytica, 6 Mannheimia glucosida, and 4 Pasteurella trehalosi strains by comparative nucleotide sequence analysis. The OmpA proteins of M. haemolytica and M. glucosida contain four hypervariable domains located at the distal ends of the surface-exposed loops. The hypervariable domains of OmpA proteins from bovine and ovine M. haemolytica isolates are very different but are highly conserved among strains from each of these two host species. Fourteen different alleles representing four distinct phylogenetic classes, classes I to IV, were identified in M. haemolytica and M. glucosida. Class I, II, and IV alleles were associated with bovine M. haemolytica, ovine M. haemolytica, and M. glucosida strains, respectively, whereas class III alleles were present in certain M. haemolytica and M. glucosida isolates. Class I and II alleles were associated with divergent lineages of bovine and ovine M. haemolytica strains, respectively, indicating a history of horizontal DNA transfer and assortative (entire gene) recombination. Class III alleles have mosaic structures and were derived by horizontal DNA transfer and intragenic recombination. Our findings suggest that OmpA is under strong selective pressure from the host species and that it plays an important role in host adaptation. It is proposed that the OmpA protein of M. haemolytica acts as a ligand and is involved in binding to specific host cell receptor molecules in cattle and sheep. P. trehalosi expresses two OmpA homologs that are encoded by different tandemly arranged ompA genes. The P. trehalosi ompA genes are highly diverged from those of M. haemolytica and M. glucosida, and evidence is presented to suggest that at least one of these genes was acquired by horizontal DNA transfer.
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Godefroy, Sylvie, Nathalie Corvaia, Daniel Schmitt, Jean-Pierre Aubry, Jean-Yves Bonnefoy, Pascale Jeannin i Marie-Jeanne Staquet. "Outer membrane protein A (OmpA) activates human epidermal Langerhans cells". European Journal of Cell Biology 82, nr 4 (kwiecień 2003): 193–200. http://dx.doi.org/10.1078/0171-9335-00303.
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Freudl, Roland, Michael Klose i Ulf Henning. "Export and sorting of theEscherichia coli outer membrane protein OmpA". Journal of Bioenergetics and Biomembranes 22, nr 3 (czerwiec 1990): 441–49. http://dx.doi.org/10.1007/bf00763176.
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Arif, Eman Dhahir, Nahla Mohammad Saeed, Shwan Kamal Rachid, Hiewa Othman Dyary i Peshnyar M. A. Rashid. "Expression Level of the mip, pmp18D, and ompA Genes in Chlamydia abortus Isolated from Aborted Ewes". Polish Journal of Microbiology 71, nr 1 (1.03.2022): 115–21. http://dx.doi.org/10.33073/pjm-2022-014.
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Abstract In this manuscript, we report the proteins macrophage infectivity potentiator (mip, CAB080), major outer membrane protein (momp, CAB048), and polymorphic outer membrane protein (pmp18D, CAB776) that are expressed in different times of pregnancy in mice infected with Chlamydia abortus. Enzootic abortion of ewes (EAE) by C. abortus, an obligate intracellular pathogen, is a critical zoonotic disease-causing significant economic loss to livestock farming globally. This study was carried out for the detection and characterization of macrophage infectivity potentiator (mip, CAB080), major outer membrane protein (momp, CAB048), and polymorphic outer membrane protein (pmp18D, CAB776) using RT-qPCR. These proteins are believed to be expressed as virulence factors in C. abortus isolated from aborted ewes. BALB/c mice (pregnant and nonpregnant) were used as an animal model to be injected intraperitoneally with C. abortus culture in Vero cells since the endometrial lymphoid tissues of these animals resembles that of ewes. Also, the short duration of pregnancy in mice makes them a suitable animal model for obstetric studies. Tissue samples were taken from the mice after 10, 15, and 20 days of pregnancy to compare the expression of the genes mip, pmp18D, and ompA. Transcription level was quantified using RT-qPCR, the GAPDH transcription quantification, as a normalization signal. Abortion occurred in pregnant mice, and apparent differences between the transcriptional levels of the mip, pmp18D, and ompA genes in the samples taken during different time intervals of pregnancy were not observed (p > 0.05). The result indicated that the three bacterial genes, mip, pmp18D, and ompA, play a role as virulence factors in abortion and are differentially expressed in pregnant and nonpregnant animals. Inactivation of the genes is suggested to confirm the hypothesis.
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Baldermann, C., A. Lupas, J. Lubieniecki i H. Engelhardt. "The Regulated Outer Membrane Protein Omp21 from Comamonas acidovorans Is Identified as a Member of a New Family of Eight-Stranded β-Sheet Proteins by Its Sequence and Properties". Journal of Bacteriology 180, nr 15 (1.08.1998): 3741–49. http://dx.doi.org/10.1128/jb.180.15.3741-3749.1998.
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ABSTRACT Omp21, a minor outer membrane protein of the soil bacteriumComamonas acidovorans, was purified from a spontaneous mutant lacking a surface layer and long-chain lipopolysaccharide. Omp21 synthesis is enhanced by oxygen depletion, and the protein has a variable electrophoretic mobility in sodium dodecyl sulfate-polyacrylamide gel electrophoresis due to its heat-modifiable behavior. The structural gene omp21 encodes a precursor of 204 amino acids with a putative signal peptide of 21 amino acids. Mature Omp21 is a typical outer membrane protein with a high content of β structure as determined by infrared spectroscopy. Sequence comparisons show that it belongs to a new outer membrane protein family, characterized by eight amphipathic β strands, which includes virulence proteins, such as the neisserial opacity proteins,Salmonella typhimurium Rck, and Yersinia enterocolitica Ail, as well as the major outer membrane proteins OmpA from Escherichia coli and OprF fromPseudomonas aeruginosa.
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Prasadarao, Nemani V., Carol A. Wass, Monique F. Stins, Hiroyuki Shimada i Kwang Sik Kim. "Outer Membrane Protein A-Promoted Actin Condensation of Brain Microvascular Endothelial Cells Is Required for Escherichia coli Invasion". Infection and Immunity 67, nr 11 (1.11.1999): 5775–83. http://dx.doi.org/10.1128/iai.67.11.5775-5783.1999.
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ABSTRACT Escherichia coli is the most common gram-negative bacterium that causes meningitis during the neonatal period. We have previously shown that the entry of circulating E. coliorganisms into the central nervous system is due to their ability to invade the blood-brain barrier, which is composed of a layer of brain microvascular endothelial cells (BMEC). In this report, we show by transmission electron microscopy that E. coli transmigrates through BMEC in an enclosed vacuole without intracellular multiplication. The microfilament-disrupting agents cytochalasin D and latrunculin A completely blocked E. coli invasion of BMEC. Cells treated with the microtubule inhibitors nocodazole, colchicine, vincristin, and vinblastine and the microtubule-stabilizing agent taxol also exhibited 50 to 60% inhibition of E. coli invasion. Confocal laser scanning fluorescence microscopy showed F-actin condensation associated with the invasive E. coli but no alterations in microtubule distribution. These results suggest thatE. coli uses a microfilament-dependent phagocytosis-like endocytic mechanism for invasion of BMEC. Previously we showed that OmpA expression significantly enhances the E. coliinvasion of BMEC. We therefore examined whether OmpA expression is related to the recruitment of F-actin. OmpA+ E. coli induced the accumulation of actin in BMEC to a level similar to that induced by the parental strain, whereas OmpA− E. coli did not. Despite the presence of OmpA, a noninvasive E. coli isolate, however, did not show F-actin condensation. OmpA+-E. coli-associated condensation of F-actin was blocked by synthetic peptides corresponding to the N-terminal extracellular domains of OmpA as well as BMEC receptor analogues for OmpA, chitooligomers (GlcNAcβ1-4GlcNAc oligomers). These findings suggest that OmpA interaction is critical for the expression or modulation of other bacterial proteins that will subsequently cause actin accumulation for the uptake of bacteria.
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Skerniškytė, Jūratė, Emilija Karazijaitė, Julien Deschamps, Renatas Krasauskas, Romain Briandet i Edita Sužiedėlienė. "The Mutation of Conservative Asp268 Residue in the Peptidoglycan-Associated Domain of the OmpA Protein Affects Multiple Acinetobacter baumannii Virulence Characteristics". Molecules 24, nr 10 (22.05.2019): 1972. http://dx.doi.org/10.3390/molecules24101972.
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Acinetobacter baumannii is a nosocomial human pathogen of increasing concern due to its multidrug resistance profile. The outer membrane protein A (OmpA) is an abundant bacterial cell surface component involved in A. baumannii pathogenesis. It has been shown that the C-terminal domain of OmpA is located in the periplasm and non-covalently associates with the peptidoglycan layer via two conserved amino acids, thereby anchoring OmpA to the cell wall. Here, we investigated the role of one of the respective residues, D268 in OmpA of A. baumannii clinical strain Ab169, on its virulence characteristics by complementing the ΔompA mutant with the plasmid-borne ompAD268A allele. We show that while restoring the impaired biofilm formation of the ΔompA strain, the Ab169ompAD268A mutant tended to form bacterial filaments, indicating the abnormalities in cell division. Moreover, the Ab169 OmpA D268-mediated association to peptidoglycan was required for the manifestation of twitching motility, desiccation resistance, serum-induced killing, adhesion to epithelial cells and virulence in a nematode infection model, although it was dispensable for the uptake of β-lactam antibiotics by outer membrane vesicles. Overall, the results of this study demonstrate that the OmpA C-terminal domain-mediated association to peptidoglycan is critical for a number of virulent properties displayed by A. baumannii outside and within the host.
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Nicholson, Tracy F., Kristin M. Watts i David A. Hunstad. "OmpA of Uropathogenic Escherichia coli Promotes Postinvasion Pathogenesis of Cystitis". Infection and Immunity 77, nr 12 (21.09.2009): 5245–51. http://dx.doi.org/10.1128/iai.00670-09.
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ABSTRACT Type 1 pilus directs bladder epithelial binding and invasion by uropathogenic Escherichia coli (UPEC) in the initial stage of cystitis, but the bacterial determinants of postinvasion events in the pathogenesis of cystitis are largely undetermined. We show here that the UPEC outer membrane protein A (OmpA), a monomeric, major, integral protein component of the bacterial outer membrane, functions as a critical determinant of intracellular virulence for UPEC, promoting persistent infection within bladder epithelium. Using a murine urinary tract infection (UTI) model, we demonstrate that whereas deletion of the UPEC ompA gene did not disrupt initial epithelial binding and invasion by UPEC, it did preclude completion of the intracellular bacterial community (IBC) pathway, accompanied by diminishing bacterial loads in the bladder. This defect in epithelial persistence of the ompA mutant was enhanced in competitive infections with wild-type UPEC. Microscopic examinations revealed that the ompA mutant formed significantly fewer IBCs, and those that were initiated were unable to progress past the early stages of maturation. These defects could be corrected by complementation of ompA. In addition, expression of ompA during wild-type UTI was sharply increased at time points correlated with IBC development and the arrival of host immune effector cells. Our findings establish OmpA as a key UPEC virulence factor that functions after epithelial invasion to facilitate IBC maturation and chronic bacterial persistence.
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Singh, Shiva P., Yvonne U. Williams, Stephanie Miller i Hiroshi Nikaido. "The C-Terminal Domain of Salmonella enterica Serovar Typhimurium OmpA Is an Immunodominant Antigen in Mice but Appears To Be Only Partially Exposed on the Bacterial Cell Surface". Infection and Immunity 71, nr 7 (lipiec 2003): 3937–46. http://dx.doi.org/10.1128/iai.71.7.3937-3946.2003.
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ABSTRACT We examined the way the major outer membrane protein OmpA of Salmonella enterica serovar Typhimurium is recognized by the mouse immune system, by raising a panel of 12 monoclonal antibodies (MAbs) against this protein. Interaction between OmpA and these MAbs is competitively inhibited with several-hundredfold dilutions of mouse polyclonal sera obtained by immunization with live or heat-killed whole cells, suggesting that OmpA is one of the immunodominant antigens of serovar Typhimurium. All of the MAbs were specific for an identical epitope(s) located on the C-terminal domain of OmpA, as indicated by the use of OmpA fragments generated by protease or cyanogen bromide treatment and by competitive inhibition enzyme-linked immunosorbent assay. This epitope was highly conserved within (but not outside) the family Enterobacteriaceae. The strong immunogenicity of this epitope was surprising because the C-terminal domain of OmpA, usually thought to be located in the periplasm, is not expected to be exposed on the bacterial cell surface. A MAb, however, reacted in a cytofluorometry assay more strongly with outer-membrane-permeabilized cells than with untreated cells, a result supporting the predominantly periplasmic localization of the epitope. Significant, though low-level, reactivity of intact cells nevertheless suggests that in some cells the C-terminal domain of OmpA is exposed on the surface, a result consistent with the proposal that OmpA can fold into one of the two alternate conformations.
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Bi, Baoliang, Yin Yuan, Dan Jia, Wansheng Jiang, Hui Yan, Gailing Yuan i Yu Gao. "Identification and Pathogenicity of Emerging Fish Pathogen Acinetobacter johnsonii from a Disease Outbreak in Rainbow Trout (Oncorhynchus mykiss)". Aquaculture Research 2023 (4.02.2023): 1–13. http://dx.doi.org/10.1155/2023/1995494.
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In November 2017, a group of farmed rainbow trout (Oncorhynchus mykiss) died in Yunnan Province, China, likely due to infection. These rainbow trout exhibited slow movement, no feeding, dark body color, exophthalmia, and occasional ulcers on the body surface. Pathogens were isolated from diseased rainbow trout livers, head kidneys, spleens, and eyes, and the strain was preliminarily identified as Acinetobacter johnsonii based on morphology, biochemical tests, and 16S rRNA and rpoB sequences. The isolated strains were highly sensitive to florfenicol, ciprofloxacin, oxolinic acid, and norfloxacin but resistant to ampicillin, doxycycline, sulfadiazine, thiamphenicol, and sulfamethazine. The selected isolate was performed for the experimental infection of rainbow trout to confirm its pathogenicity. Experimentally infected fish showed disease symptoms similar to those observed in fish naturally infected with these bacteria. Vacuolar degeneration was prevalent in the liver and spleen of diseased fish. Cytoplasm volume was very high in the lymphocytes of the head kidney. The protein structure and topology of monomeric outer membrane protein A (OmpA), outer membrane protein 34 (Omp34), and a nucleoside-specific outer membrane transporter protein Tsx (OmpTsx) of A. johnsonii were predicted by AlphaFold 2. The predicted local distance difference test (pLDDT) score was used for the assessment of structure prediction. Comprehensive analysis of antigenic determinants of the OMP family member, OmpA, contains three antigenic determinants, which are 90% similar with epitopes of A. baumannii. OmpA is a recombinant protein with 35 kDa expressed in the Escherichia coli system. Based on these findings, A. johnsonii is regarded as an emerging opportunistic pathogen in farmed rainbow trout. OmpA protein can be used as a subunit vaccine candidate molecule of A. johnsonii.
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Hirakawa, Hidetada, Kazutomo Suzue, Ayako Takita i Haruyoshi Tomita. "Roles of OmpA in Type III Secretion System-Mediated Virulence of Enterohemorrhagic Escherichia coli". Pathogens 10, nr 11 (17.11.2021): 1496. http://dx.doi.org/10.3390/pathogens10111496.
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Outer membrane proteins are commonly produced by gram-negative bacteria, and they have diverse functions. A subgroup of proteins, which includes OmpA, OmpW and OmpX, is often involved in bacterial pathogenesis. Here we show that OmpA, rather than OmpW or OmpX, contributes to the virulence of enterohemorrhagic Escherichia coli (EHEC) through its type III secretion system (T3SS). Deletion of ompA decreased secretion of the T3SS proteins EspA and EspB; however, the expression level of the LEE genes that encode a set of T3SS proteins did not decrease. The ompA mutant had less abilities to form A/E lesions in host epithelial cells and lyse human red blood cells than the parent strain. Moreover, the virulence of an ompA mutant of Citrobacter rodentium (traditionally used to estimate T3SS-associated virulence in mice) was attenuated. Mice infected with the ompA mutant survived longer than those infected with the parent strain. Furthermore, mice infected with ompA developed symptoms of diarrhea more slowly than mice infected with the parent strain. Altogether, these results suggest that OmpA sustains the activity of the T3SS and is required for optimal virulence in EHEC. This work expands the roles of outer membrane proteins in bacterial pathogenesis.
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Sukumaran, Sunil K., Hiroyuki Shimada i Nemani V. Prasadarao. "Entry and Intracellular Replication of Escherichia coli K1 in Macrophages Require Expression of Outer Membrane Protein A". Infection and Immunity 71, nr 10 (październik 2003): 5951–61. http://dx.doi.org/10.1128/iai.71.10.5951-5961.2003.
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ABSTRACT Interactions between Escherichia coli K1, which causes meningitis in neonates, and macrophages have not been explored well. In this study we found that E. coli K1 was able to enter, survive, and replicate intracellularly in both murine and human macrophage cell lines, as well as in monocytes and macrophages of newborn rats. In addition, we demonstrated that OmpA + E. coli also enters and replicates in human peripheral blood monocytes in vitro. Outer membrane protein A (OmpA) expression on E. coli contributes to binding to macrophages, phagocytosis, and survival within macrophages. Opsonization with either complement proteins or antibody is not required for uptake and survival of the bacteria within the macrophages. Transmission electron microscopy and immunocytochemistry studies with the infected macrophages indicated that OmpA+ E. coli multiplies enormously in a single phagosome and bursts the cell. Internalization of OmpA+ E. coli by RAW 264.7 cells occurred by both actin- and microtubule-dependent processes, which are independent of RGD-mediated integrin receptors. Internalization and intracellular survival within phagocytic cells thus may play an important role in the development of bacteremia, which is crucial for E. coli crossing of the blood-brain barrier.
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Bista, Prabha K., Deepti Pillai i Sanjeev K. Narayanan. "Outer-Membrane Vesicles of Fusobacterium necrophorum: A Proteomic, Lipidomic, and Functional Characterization". Microorganisms 11, nr 8 (14.08.2023): 2082. http://dx.doi.org/10.3390/microorganisms11082082.
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Outer-membrane vesicles (OMVs) are extruded nanostructures shed by Gram-negative bacteria, containing periplasmic contents, and often including virulence factors with immunogenic properties. To assess their potential for use in vaccine development, we purified OMVs from the Fusobacterium necrophorum subspecies necrophorum, an opportunistic necrotic infection-causing pathogen, and characterized these structures using proteomics, lipid-profiling analyses, and cytotoxicity assays. A proteomic analysis of density-gradient-purified F. necrophorum OMVs identified 342 proteins, a large proportion of which were outer-membrane proteins (OMPs), followed by cytoplasmic proteins, based on a subcellular-localization-prediction analysis. The OMPs and toxins were among the proteins with the highest intensity identified, including the 43-kDa-OMP-, OmpA-, and OmpH-family proteins, the cell-surface protein, the FadA adhesin protein, the leukotoxin-LktA-family filamentous adhesin, the N-terminal domain of hemagglutinin, and the OMP transport protein and assembly factor. A Western blot analysis confirmed the presence of several OMPs and toxins in the F. necrophorum OMVs. The lipid-profiling analysis revealed phospholipids, sphingolipids, and acetylcarnitine as the main lipid contents of OMVs. The lactate-dehydrogenase-cytotoxicity assays showed that the OMVs had a high degree of cytotoxicity against a bovine B-lymphocyte cell line (BL-3 cells). Thus, our data suggest the need for further studies to evaluate the ability of OMVs to induce immune responses and assess their vaccine potential in vivo.
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Ayalew, Sahlu, Binu Shrestha, Marie Montelongo, Amanda E. Wilson i Anthony W. Confer. "Immunogenicity of Mannheimia haemolytica Recombinant Outer Membrane Proteins Serotype 1-Specific Antigen, OmpA, OmpP2, and OmpD15". Clinical and Vaccine Immunology 18, nr 12 (5.10.2011): 2067–74. http://dx.doi.org/10.1128/cvi.05332-11.
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ABSTRACTWe previously identifiedMannheimia haemolyticaouter membrane proteins (OMPs) that may be important immunogens by using immunoproteomic analyses. Genes for serotype 1-specific antigen (SSA-1), OmpA, OmpP2, and OmpD15 were cloned and expressed, and recombinant proteins were purified. Objective 1 of this study was to demonstrate immunogenicity of the four recombinant OMPs in mice and cattle. Objective 2 was to determine if the addition of individual recombinant OMPs or combinations of them would modify immune responsiveness of mice to the recombinant chimeric protein SAC89, containing the main epitope fromM. haemolyticaouter membrane lipoprotein PlpE and the neutralizing epitope ofM. haemolyticaleukotoxin. Mice vaccinated with recombinant OmpA (rOmpA), rSSA-1, rOmpD15, and rOmpP2 developed significant antibody responses toM. haemolyticaouter membranes and to the homologous recombinant OMP. Cattle vaccinated with rOmpA and rSSA-1 developed significant antibodies toM. haemolyticaouter membranes by day 28, whereas cattle vaccinated with rOmpD15 and rOmpP2 developed only minimal responses. Sera from cattle vaccinated with each of the recombinant proteins stimulated complement-mediated killing of the bacterium. Concurrent vaccination with SAC89 plus any of the four rOMPs singly resulted in increased endpoint anti-SAC89 titers, and for the SAC89/rSSA-1 vaccinees, the response was increased significantly. In contrast, the SAC89/P2/SSA-1 and SAC89/OmpA/P2/D15/SSA-1 combination vaccines resulted in significant decreases in anti-SAC89 antibodies compared to SAC89 vaccination alone. In conclusion, under the conditions of these experiments, vaccination of mice and cattle with rOmpA and rSSA-1 stimulated high antibody responses and may have protective vaccine potential.
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Zeng, Hui, Karamjeet Pandher i George L. Murphy. "Molecular Cloning of the Pasteurella haemolytica pomA Gene and Identification of Bovine Antibodies against PomA Surface Domains". Infection and Immunity 67, nr 9 (1.09.1999): 4968–73. http://dx.doi.org/10.1128/iai.67.9.4968-4973.1999.
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ABSTRACT The gene (pomA) encoding PomA, an OmpA-like major outer membrane protein of the bovine respiratory pathogen Pasteurella haemolytica, was cloned, and its nucleotide sequence was determined. The deduced amino acid sequence of PomA has significant identity with the sequences of other OmpA family proteins. Absorption of three different bovine immune sera with whole P. haemolytica cells resulted in a reduction of bovine immunoglobulin G reactivity with recombinant PomA in Western immunoblots, suggesting the presence of antibodies against PomA surface domains.
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Brunelle, Brian W., i George F. Sensabaugh. "The ompA Gene in Chlamydia trachomatis Differs in Phylogeny and Rate of Evolution from Other Regions of the Genome". Infection and Immunity 74, nr 1 (styczeń 2006): 578–85. http://dx.doi.org/10.1128/iai.74.1.578-585.2006.
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ABSTRACT Strains of Chlamydia trachomatis are classified into serovars based on nucleotide sequence differences in ompA, the gene that encodes the major outer membrane protein. Phylogenetic characterization of strains based on ompA, however, results in serovar groupings that are inconsistent with the distinguishing features of C. trachomatis pathobiology, e.g., tissue tropisms and disease presentation. We have compared nucleotide sequences at multiple sites distributed around the chlamydial genome from 18 strains representing 16 serovars; sampled regions included genes encoding housekeeping enzymes (totaling 2,073 bp), intergenic noncoding segments (1,612 bp), and a gene encoding a second outer membrane protein (porB; 1,023 bp), with the ompA sequence (1,194 bp) used for reference. These comparative analyses revealed substantial variation in nucleotide substitution patterns among the sampled regions, with average pairwise sequence differences ranging from 0.15% for the housekeeping genes to 12.1% for ompA. Phylogenetic characterization of the sampled genomic sequences yielded a strongly supported tree that divides the strains into groupings consistent with C. trachomatis biology and which has a topology quite distinct from the ompA tree. This phylogenetic incongruity can be accounted for by recombination of the ompA gene between different genomic backgrounds. We found, however, no evidence of recombination within or between any of the sampled regions around the C. trachomatis genome apart from ompA. Parallel analysis of published sequence data on four members of the pmp gene family are consistent with the phylogenetic analyses reported here.
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Shahryari, Shahab, Parvin Mohammadnejad i Kambiz Akbari Noghabi. "Screening of anti- Acinetobacter baumannii phytochemicals, based on the potential inhibitory effect on OmpA and OmpW functions". Royal Society Open Science 8, nr 8 (sierpień 2021): 201652. http://dx.doi.org/10.1098/rsos.201652.
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Therapeutic options including last-line or combined antibiotic therapies for multi-drug-resistant strains of Acinetobacter baumannii are ineffective. The outer membrane protein A (OmpA) and outer membrane protein W (OmpW) are two porins known for their different cellular functions. Identification of natural compounds with the potentials to block these putative porins can attenuate the growth of the bacteria and control the relating diseases. The current work aimed to screen a library of 384 phytochemicals according to their potentials to be used as a drug, and potentials to inhibit the function of OmpA and OmpW in A. baumannii . The phytocompounds were initially screened based on their physico-chemical, absorption, distribution, metabolism, excretion and toxicity (ADMET) drug-like properties. Afterwards, the selected ligands were subjected to standard docking calculations against the predicted three-dimensional structure of OmpA and OmpW in A. baumannii . We identified three phytochemicals (isosakuranetin, aloe-emodin and pinocembrin) possessing appreciable binding affinity towards the selected binding pocket of OmpA and OmpW. Molecular dynamics simulation analysis confirmed the stability of the complexes. Among them, isosakuranetin was suggested as the best phytocompound for further in vitro and in vivo study.
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Noh, Susan M., Kelly A. Brayton, Donald P. Knowles, Joseph T. Agnes, Michael J. Dark, Wendy C. Brown, Timothy V. Baszler i Guy H. Palmer. "Differential Expression and Sequence Conservation of the Anaplasma marginale msp2 Gene Superfamily Outer Membrane Proteins". Infection and Immunity 74, nr 6 (czerwiec 2006): 3471–79. http://dx.doi.org/10.1128/iai.01843-05.
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ABSTRACT Bacterial pathogens in the genera Anaplasma and Ehrlichia encode a protein superfamily, pfam01617, which includes the predominant outer membrane proteins (OMPs) of each species, major surface protein 2 (MSP2) and MSP3 of Anaplasma marginale and Anaplasma ovis, Anaplasma phagocytophilum MSP2 (p44), Ehrlichia chaffeensis p28-OMP, Ehrlichia canis p30, and Ehrlichia ruminantium MAP1, and has been shown to be involved in both antigenic variation within the mammalian host and differential expression between the mammalian and arthropod hosts. Recently, complete sequencing of the A. marginale genome has identified an expanded set of genes, designated omp1-14, encoding new members of this superfamily. Transcriptional analysis indicated that, with the exception of the three smallest open reading frames, omp2, omp3, and omp6, these superfamily genes are transcribed in A. marginale-infected erythrocytes, tick midgut and salivary glands, and the IDE8 tick cell line. OMPs 1, 4, 7 to 9, and 11 were confirmed to be expressed as proteins by A. marginale within infected erythrocytes, with expression being either markedly lower (OMPs 1, 4, and 7 to 9) or absent (OMP11) in infected tick cells, which reflected regulation at the transcript level. Although the pfam01617 superfamily includes the antigenically variable MSP2 and MSP3 surface proteins, analysis of the omp1-14 sequences throughout a cycle of acute and persistent infection in the mammalian host and tick transmission reveals a high degree of conservation, an observation supported by sequence comparisons between the St. Maries strain and Florida strain genomes.
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Feng, Hui-Min, Ted Whitworth, Juan P. Olano, Vsevolod L. Popov i David H. Walker. "Fc-Dependent Polyclonal Antibodies and Antibodies to Outer Membrane Proteins A and B, but Not to Lipopolysaccharide, Protect SCID Mice against Fatal Rickettsia conorii Infection". Infection and Immunity 72, nr 4 (kwiecień 2004): 2222–28. http://dx.doi.org/10.1128/iai.72.4.2222-2228.2004.
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ABSTRACT An emphasis on cellular immunity against Rickettsia has led to neglect of analysis of the role of antibody. The availability of an excellent mouse model of spotted fever rickettsiosis enabled investigation of a potential role of antibody in immunity to Rickettsia conorii. C3H severe combined immunodeficiency (SCID) mice were passively transfused with monoclonal antibodies against rickettsial outer membrane protein A (OmpA), OmpB, or lipopolysaccharide (LPS), polyclonal anti-R. conorii serum, Fab fragments of polyclonal antiserum, or no antibodies and then challenged 48 h later with 10 50% lethal doses (LD50) of R. conorii. All mice that received monoclonal antibodies against OmpA and two of four mice that received monoclonal antibodies against OmpB or polyclonal antisera were completely protected, but the recipients of anti-LPS antibodies or the Fab fragments were not protected. Polyclonal antibody treatment of C3H SCID mice that had been infected with 10 LD50 of R. conorii 4 or 5 days earlier prolonged the life of the infected mice from 10.4 to 22.5 days and resulted in decreased levels of infectious rickettsiae in the spleen and liver 24 and 48 h later. Treatment with protective antibodies resulted in the development of large aggregates of R. conorii antigens in splenic macrophages and intraphagolysosomal rickettsial death and digestion. The kinetics of development of antibodies to R. conorii determined by immunoblotting revealed antibodies to LPS on day 6 and antibodies to OmpA and OmpB on day 12, when recovery from the infection had already occurred. Antibodies to particular epitopes of OmpA and OmpB may protect against reinfection, but they may not play a key role in immunity against primary infection. Antibodies might be useful for treating infections with antibiotic-resistant organisms, and some B-cell epitopes should be included in a subunit vaccine.
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Liao, Chunyu, Miguel C. Santoscoy, Julia Craft, Chiron Anderson, Michelle L. Soupir i Laura R. Jarboe. "Allelic variation of Escherichia coli outer membrane protein A: Impact on cell surface properties, stress tolerance and allele distribution". PLOS ONE 17, nr 10 (13.10.2022): e0276046. http://dx.doi.org/10.1371/journal.pone.0276046.
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Outer membrane protein A (OmpA) is one of the most abundant outer membrane proteins of Gram-negative bacteria and is known to have patterns of sequence variations at certain amino acids—allelic variation—in Escherichia coli. Here we subjected seven exemplar OmpA alleles expressed in a K-12 (MG1655) ΔompA background to further characterization. These alleles were observed to significantly impact cell surface charge (zeta potential), cell surface hydrophobicity, biofilm formation, sensitivity to killing by neutrophil elastase, and specific growth rate at 42°C and in the presence of acetate, demonstrating that OmpA is an attractive target for engineering cell surface properties and industrial phenotypes. It was also observed that cell surface charge and biofilm formation both significantly correlate with cell surface hydrophobicity, a cell property that is increasingly intriguing for bioproduction. While there was poor alignment between the observed experimental values relative to the known sequence variation, differences in hydrophobicity and biofilm formation did correspond to the identity of residue 203 (N vs T), located within the proposed dimerization domain. The relative abundance of the (I, δ) allele was increased in extraintestinal pathogenic E. coli (ExPEC) isolates relative to environmental isolates, with a corresponding decrease in (I, α) alleles in ExPEC relative to environmental isolates. The (I, α) and (I, δ) alleles differ at positions 203 and 251. Variations in distribution were also observed among ExPEC types and phylotypes. Thus, OmpA allelic variation and its influence on OmpA function warrant further investigation.