Journal articles: 'Microbial peptides'

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Matsuzaki, K. "Why and how are peptide-lipid interactions utilized for self defence?" Biochemical Society Transactions 29, no. 4 (August 1, 2001): 598–601. http://dx.doi.org/10.1042/bst0290598.

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Animals defend themselves against invading pathogenic micro-organisms by utilizing cationic anti-microbial peptides, which rapidly kill various micro-organisms without exerting toxicity against the host. Physicochemical peptide-lipid interactions provide attractive mechanisms for innate immunity. Many of these peptides form amphipathic secondary structures (α-helices and β-sheets) which can selectively interact with anionic bacterial membranes by electrostatic interaction. Rapid, peptide-induced membrane permeabilization is an effective mechanism of anti-microbial action. Magainin 2 from frog skin forms a dynamic peptide-lipid supramolecular-complex pore that allows mutually coupled transmembrane transport of ions and lipids. The peptide molecule is internalized upon the disintegration of the pore. Several anti-microbial peptides are known to work synergistically.

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Dang, Xiangli, and Guangshun Wang. "Spotlight on the Selected New Antimicrobial Innate Immune Peptides Discovered During 2015-2019." Current Topics in Medicinal Chemistry 20, no. 32 (December 3, 2020): 2984–98. http://dx.doi.org/10.2174/1568026620666201022143625.

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Background: Antibiotic resistance is a global issue and new anti-microbials are required. Introduction: Anti-microbial peptides are important players of host innate immune systems that prevent infections. Due to their ability to eliminate drug-resistant pathogens, AMPs are promising candidates for developing the next generation of anti-microbials. Methods: The anti-microbial peptide database provides a useful tool for searching, predicting, and designing new AMPs. In the period from 2015-2019, ~500 new natural peptides have been registered. Results: This article highlights a select set of new AMP members with interesting properties. Teixobactin is a cell wall inhibiting peptide antibiotic, while darobactin inhibits a chaperone and translocator for outer membrane proteins. Remarkably, cOB1, a sex pheromone from commensal enterococci, restricts the growth of multidrug-resistant Enterococcus faecalis in the gut at a picomolar concentration. A novel proline-rich AMP has been found in a plant Brassica napus. A shrimp peptide MjPen-II comprises three different sequence domains: serine-rich, proline-rich, and cysteine-rich regions. Surprisingly, an amphibian peptide urumin specifically inhibits H1 hemagglutinin-bearing influenza A virus. Defensins are abundant and typically consist of three pairs of intramolecular disulfide bonds. However, rat rattusin dimerizes via forming five pairs of intermolecular disulfide bonds. While human LL-37 can be induced by vitamin D, vitamin A induces the expression of resistin-like molecule alpha (RELMα) in mice. The isolation and characterization of an alternative human cathelicidin peptide, TLN-58, substantiates the concept of one gene multiple peptides. The involvement of a fly AMP nemuri in sleep induction may promote the research on the relationship between sleep and infection control. Conclusion: The functional roles of AMPs continue to grow and the general term “innate immune peptides” becomes useful. These discoveries widen our view on antimicrobial peptides and may open new opportunities for developing novel peptide therapeutics for different applications.

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Cytryńska, Małgorzata, and Agnieszka Zdybicka-Barabas. "Defense peptides: recent developments." Biomolecular Concepts 6, no. 4 (August 1, 2015): 237–51. http://dx.doi.org/10.1515/bmc-2015-0014.

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AbstractDefense peptides are small amphipathic molecules that exhibit antimicrobial, antitumor, antiviral, and immunomodulatory properties. This review summarizes current knowledge on the mechanisms of antimicrobial activity of cationic and anionic defense peptides, indicating peptide-based as well as microbial cell-based factors affecting this activity. The peptide-based factors include charge, hydrophibicity, and amphipathicity, whereas the pathogen-based factors are membrane lipid composition, presence of sterols, membrane fluidity, cell wall components, and secreted factors such as extracellular proteinases. Since defense peptides have been considered very promising molecules that could replace conventional antibiotics in the era of drug-resistant pathogens, the issue of microbial resistance to antimicrobial peptides (AMPs) is addressed. Furthermore, selected approaches employed for optimization and de novo design of effective AMPs based on the properties recognized as important for the function of natural defense peptides are presented.

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Ruiz, Pedro J., Hideki Garren, David L. Hirschberg, Annette M. Langer-Gould, Mia Levite, Marcela V. Karpuj, Scott Southwood, Alessandro Sette, Paul Conlon, and Lawrence Steinman. "Microbial Epitopes Act as Altered Peptide Ligands to Prevent Experimental Autoimmune Encephalomyelitis." Journal of Experimental Medicine 189, no. 8 (April 19, 1999): 1275–84. http://dx.doi.org/10.1084/jem.189.8.1275.

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Molecular mimicry refers to structural homologies between a self-protein and a microbial protein. A major epitope of myelin basic protein (MBP), p87–99 (VHFFKNIVTPRTP), induces experimental autoimmune encephalomyelitis (EAE). VHFFK contains the major residues for binding of this self-molecule to T cell receptor (TCR) and to the major histocompatibility complex. Peptides from papilloma virus strains containing the motif VHFFK induce EAE. A peptide from human papilloma virus type 40 (HPV 40) containing VHFFR, and one from HPV 32 containing VHFFH, prevented EAE. A sequence from Bacillus subtilis (RKVVTDFFKNIPQRI) also prevented EAE. T cell lines, producing IL-4 and specific for these microbial peptides, suppressed EAE. Thus, microbial peptides, differing from the core motif of the self-antigen, MBPp87–99, function as altered peptide ligands, and behave as TCR antagonists, in the modulation of autoimmune disease.

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Grogan, Jane L., Achim Kramer, Axel Nogai, Liying Dong, Manuela Ohde, Jens Schneider-Mergener, and Thomas Kamradt. "Cross-Reactivity of Myelin Basic Protein-Specific T Cells with Multiple Microbial Peptides: Experimental Autoimmune Encephalomyelitis Induction in TCR Transgenic Mice." Journal of Immunology 163, no. 7 (October 1, 1999): 3764–70. http://dx.doi.org/10.4049/jimmunol.163.7.3764.

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Abstract Activation of autoreactive T cells is a crucial event in the pathogenesis of autoimmune diseases. Cross-reactivity between microbial and self Ags (molecular mimicry) is one hypothesis that could explain the activation of autoreactive T cells. We have systematically examined this hypothesis in experimental autoimmune encephalomyelitis using mice bearing exclusively myelin basic protein (MBP)-specific T cells (designated T+ α−). A peptide substitution analysis was performed in which each residue of the MBPAc1–11 peptide was exchanged by all 20 naturally occurring amino acids. This allowed the definition of the motif (supertope) that is recognized by the MBPAc1–11-specific T cells. The supertope was used to screen protein databases (SwissProt and TREMBL). By the search, 832 peptides of microbial origin were identified and synthesized. Of these, 61 peptides induced proliferation of the MBPAc1–11-specific transgenic T cells in vitro. Thus, the definition of a supertope by global amino acid substitution can identify multiple microbial mimic peptides that activate an encephalitogenic TCR. Peptides with only two native MBP-residues were sufficient to activate MBPAc1–11-specific T cells in vitro, and experimental autoimmune encephalomyelitis could be induced by immunizing mice with a mimic peptide with only four native MBP residues.

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RUISSEN, Anita L. A., Jasper GROENINK, Eva J. HELMERHORST, Els WALGREEN-WETERINGS, Wim van't HOF, Enno C. I. VEERMAN, and Arie V. NIEUW AMERONGEN. "Effects of histatin 5 and derived peptides on Candida albicans." Biochemical Journal 356, no. 2 (May 24, 2001): 361–68. http://dx.doi.org/10.1042/bj3560361.

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Three anti-microbial peptides were compared with respect to their killing activity against Candida albicans and their ability to disturb its cellular and internal membranes. Histatin 5 is an anti-fungal peptide occurring naturally in human saliva, while dhvar4 and dhvar5 are variants of its active domain, with increased anti-microbial activity. dhvar4has increased amphipathicity compared with histatin 5, whereas dhvar5has amphipathicity comparable with that of histatin 5. All three peptides caused depolarization of the cytoplasmic and/or mitochondrial membrane, indicating membranolytic activity. For the variant peptides both depolarization and killing occurred at a faster rate. With FITC-labelled peptides, no association with the cytoplasmic membrane was observed, contradicting the formation of permanent transmembrane multimeric peptide pores. Instead, the peptides were internalized and act on internal membranes, as demonstrated with mitochondrion- and vacuole-specific markers. In comparison with histatin 5, the variant peptides showed a more destructive effect on mitochondria. Entry of the peptides and subsequent killing were dependent on the metabolic state of the cells. Blocking of the mitochondrial activity led to complete protection against histatin 5 activity, whereas that of dhvar4 was hardly affected and that of dhvar5 was affected only intermediately.

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Nagler, Adi, Shelly Kalaora, Deborah Gitta Rosenberg, Michal Alon, Eilon Barnea, Ronen Levy, Kevin Vervier, et al. "672 Identification of microbial-derived HLA-bound peptides in melanoma." Journal for ImmunoTherapy of Cancer 8, Suppl 3 (November 2020): A710. http://dx.doi.org/10.1136/jitc-2020-sitc2020.0672.

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BackgroundThe query for tumor shared and neo-antigens as a therapeutic approach has been the focus of cancer immunology for the past two decades. Notably, these peptide sequences can bind to HLA molecules and present on the cell surface, subsequently to be recognized by T-cell receptors (TCRs), activating the immune system and so facilitating in tumor rejection.1–3 The search for new origins of targetable types of HLA peptides is consistently growing, and new studies show peptides that are derived from non-canonical open reading frames (ORFs), altered translation, proteasome splicing, viral proteins and more.4–6 In light of the new findings, showing the important role of intra-tumor and gut bacteria in tumor-genesis and their effect on the immune response,7–10 we went on a quest for discovering whether intracellular bacteria antigens can be presented by tumor cells, and whether these antigens may elicit an immune response.MethodsCombination of HLA peptidomics with 16S rDNA sequencing.ResultsCombination of HLA peptidomics with 16S rDNA sequencing of 17 melanoma metastasis derived from 9 different patients, lead us to the unbiased identification of an intracellular bacterial peptide repertoire presented on HLA-I and HLA-II molecules. We were able to validate these results by co-culturing the bacterial species identified by 16S sequencing with the patient derived melanoma cells, further validating the peptide’s presentation by preforming HLA peptidomics on the infected cells. Importantly, we were able to identify common bacterial peptides from different metastases of the same patient as well as from different patients. Some of the common bacterial peptides, as well as others, were able to elicit an immune response by the autologous tumor infiltrating lymphocytes (TILs), suggesting potential therapeutic implications of these peptides.ConclusionsThe insights gathered through this study elucidate the effect of intra-tumor bacteria on the immune response and so, may lead to the development of novel clinical applications.ReferencesNeefjes J, Jongsma ML, Paul P, Bakke O. Towards a systems understanding of MHC class I and MHC class II antigen presentation. Nat Rev Immunol 2011;11: 823–836.Stronen E, Toebes M, Kelderman S, et al. Targeting of cancer neoantigens with donor-derived T cell receptor repertoires. Science 2016; 352: 1337–1341.Rosenberg SA, Restifo NP. Adoptive cell transfer as personalized immunotherapy for human cancer. Science 2015; 348: 62–68.Chen J, Brunner AD, Cogan JZ, et al. Pervasive functional translation of noncanonical human open reading frames. Science 2020; 367: 1140–1146.Starck SR, Shastri N. Nowhere to hide: unconventional translation yields cryptic peptides for immune surveillance. Immunol Rev 2016;272:8–16.Croft NP, Smith SA, Pickering J, et al. Most viral peptides displayed by class I MHC on infected cells are immunogenic. Proc Natl Acad Sci U S A 2019; 116: 3112–3117.Gopalakrishnan V, Spencer CN, Nezi L, et al. Gut microbiome modulates response to anti-PD-1 immunotherapy in melanoma patients. Science 2018;359:97–103.Routy B, Le Chatelier E, Derosa L, et al. Gut microbiome influences efficacy of PD-1-based immunotherapy against epithelial tumors. Science 2018;359:91–97.Matson V, Fessler J, Bao R, et al. The commensal microbiome is associated with anti-PD-1 efficacy in metastatic melanoma patients. Science 2018;359:104–108.10. Nejman D, Livyatan I, Fuks G et al. The human tumor microbiome is composed of tumor type-specific intracellular bacteria. Science 2020;368:973–980.

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Wallace, R. J. "Acetylation of peptides inhibits their degradation by rumen micro-organisms." British Journal of Nutrition 68, no. 2 (September 1992): 365–72. http://dx.doi.org/10.1079/bjn19920095.

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Proteins and peptides were acetylated using acetic anhydride in order to block their N-terminal amino groups and thereby to prevent their hydrolysis by rumen microbial aminopeptidases. The effects of acetylation on peptide breakdown and ammonia production were determined by incubating unmodified and acetylated substrates with sheep rumen micro-organisms in vitro. Ammonia production from casein and lactalbumin was affected little by acetylation, but acetylation of the corresponding enzymic hydrolysates caused ammonia production to be more than halved after 3.6 h incubation. Estimation of peptides remaining in rumen fluid showed that the decreased ammonia production was a consequence of peptides being hydrolysed more slowly. Acetylated Ala-Ala, Ala-Ala-Ala (Ala3), Leu-Gly-Gly, Phe-Gly-Gly and Val-Gly-Ser-Glu survived incubation with rumen fluid in vitro for 6 h, whereas almost none of the corresponding unmodified peptides was present at 6 h. The protection afforded to larger pure peptides was less reliable: for example, 72% of acetylated bradykinin was hydrolysed after 1 h.N-Acetyl Ala3had only a minor inhibitory effect on the breakdown of Ala3and Ala4, suggesting that although acetyl peptides were broken down more slowly than unmodified peptides they did not inhibit peptidase activity.

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Ramón-García, Santiago, Ralf Mikut, Carol Ng, Serge Ruden, Rudolf Volkmer, Markus Reischl, Kai Hilpert, and Charles J. Thompson. "Targeting Mycobacterium tuberculosis and Other Microbial Pathogens Using Improved Synthetic Antibacterial Peptides." Antimicrobial Agents and Chemotherapy 57, no. 5 (March 11, 2013): 2295–303. http://dx.doi.org/10.1128/aac.00175-13.

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ABSTRACTThe lack of effective therapies for treating tuberculosis (TB) is a global health problem. WhileMycobacterium tuberculosisis notoriously resistant to most available antibiotics, we identified synthetic short cationic antimicrobial peptides that were active at low micromolar concentrations (less than 10 μM). These small peptides (averaging 10 amino acids) had remarkably broad spectra of antimicrobial activities against both bacterial and fungal pathogens and an indication of low cytotoxicity. In addition, their antimicrobial activities displayed various degrees of species specificity that were not related to taxonomy. For example,Candida albicansandStaphylococcus aureuswere the best surrogates to predict peptide activity againstM. tuberculosis, whileMycobacterium smegmatiswas a poor surrogate. Principle component analysis of activity spectrum profiles identified unique features associated with activity againstM. tuberculosisthat reflect their distinctive amino acid composition; active peptides were more hydrophobic and cationic, reflecting increased tryptophan with compensating decreases in valine and other uncharged amino acids and increased lysine. These studies provide foundations for development of cationic antimicrobial peptides as potential new therapeutic agents for TB treatment.

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Hearn, Jack, Jacob M. Riveron, Helen Irving, Gareth D. Weedall, and Charles S. Wondji. "Gene Conversion Explains Elevated Diversity in the Immunity Modulating APL1 Gene of the Malaria Vector Anopheles funestus." Genes 13, no. 6 (June 20, 2022): 1102. http://dx.doi.org/10.3390/genes13061102.

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Leucine-rich repeat proteins and antimicrobial peptides are the key components of the innate immune response to Plasmodium and other microbial pathogens in Anopheles mosquitoes. The APL1 gene of the malaria vector Anopheles funestus has exceptional levels of non-synonymous polymorphism across the range of An. funestus, with an average πn of 0.027 versus a genome-wide average of 0.002, and πn is consistently high in populations across Africa. Elevated APL1 diversity was consistent between the independent pooled-template and target-enrichment datasets, however no link between APL1 diversity and insecticide resistance was observed. Although lacking the diversity of APL1, two further mosquito innate-immunity genes of the gambicin anti-microbial peptide family had πn/πs ratios greater than one, possibly driven by either positive or balancing selection. The cecropin antimicrobial peptides were expressed much more highly than other anti-microbial peptide genes, a result discordant with current models of anti-microbial peptide activity. The observed APL1 diversity likely results from gene conversion between paralogues, as evidenced by shared polymorphisms, overlapping read mappings, and recombination events among paralogues. In conclusion, we hypothesize that higher gene expression of APL1 than its paralogues is correlated with a more open chromatin formation, which enhances gene conversion and elevated diversity at this locus.

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Sun, Xiaopeng, Min Wang, Chuanjin Xu, Shanglong Wang, Li Li, Shengcan Zou, Jia Yu, and Yuxi Wei. "Positive Effect of a Pea–Clam Two-Peptide Composite on Hypertension and Organ Protection in Spontaneously Hypertensive Rats." Nutrients 14, no. 19 (September 30, 2022): 4069. http://dx.doi.org/10.3390/nu14194069.

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In the present study, we prepared pea peptides with high angiotensin-converting enzyme (ACE) inhibitory activity in vitro using an enzymatic hydrolysis of pea protein and compounded them with clam peptides to obtain a pea-clam double peptide. The effects of the two-peptide composite and pea peptides on hypertension and the damage-repair of corresponding organs were studied in spontaneously hypertensive rats (SHRs). We found that both pea peptides and the two-peptide composite significantly reduced the blood pressure upon a single or long-term intragastric administration, with the two-peptide composite being more effective. Mechanistically, we found that the two-peptide composite could regulate the renal renin-angiotensin system (RAS), rebalance gut microbial dysbiosis, decrease renal and myocardial fibrosis, and improve renal and cardiac function and vascular remodeling. Additionally, hippocampal lesions caused by hypertension were also eliminated after two-peptide composite administration. Our research provides a scientific basis for the use of this two-peptide composite as a safe antihypertension ingredient in functional foods.

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Otvos Jr., Laszlo. "Immunomodulatory effects of anti-microbial peptides." Acta Microbiologica et Immunologica Hungarica 63, no. 3 (September 2016): 257–77. http://dx.doi.org/10.1556/030.63.2016.005.

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Kato, Hajime, Susumu Y. Imanishi, Kiyomi Tsuji, and Ken-ichi Harada. "Microbial degradation of cyanobacterial cyclic peptides." Water Research 41, no. 8 (April 2007): 1754–62. http://dx.doi.org/10.1016/j.watres.2007.01.003.

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Egorov, Tsezi A., Tatyana I. Odintsova, Vitaliy A. Pukhalsky, and Eugene V. Grishin. "Diversity of wheat anti-microbial peptides." Peptides 26, no. 11 (November 2005): 2064–73. http://dx.doi.org/10.1016/j.peptides.2005.03.007.

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Barreto-Santamaría, Adriana, Zuly Jenny Rivera, Javier Eduardo García, Hernando Curtidor, Manuel Elkin Patarroyo, Manuel Alfonso Patarroyo, and Gabriela Arévalo-Pinzón. "Shorter Antibacterial Peptide Having High Selectivity for E. coli Membranes and Low Potential for Inducing Resistance." Microorganisms 8, no. 6 (June 8, 2020): 867. http://dx.doi.org/10.3390/microorganisms8060867.

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Antimicrobial peptides (AMPs) have been recognised as a significant therapeutic option for mitigating resistant microbial infections. It has been found recently that Plasmodium falciparum-derived, 20 residue long, peptide 35409 had antibacterial and haemolytic activity, making it an AMP having reduced selectivity, and suggesting that it should be studied more extensively for obtaining new AMPs having activity solely targeting the bacterial membrane. Peptide 35409 was thus used as template for producing short synthetic peptides (<20 residues long) and evaluating their biological activity and relevant physicochemical characteristics for therapeutic use. Four of the sixteen short peptides evaluated here had activity against E. coli without any associated haemolytic effects. The 35409-1 derivative (17 residues long) had the best therapeutic characteristics as it had high selectivity for bacterial cells, stability in the presence of human sera, activity against E. coli multiresistant clinical isolates and was shorter than the original sequence. It had a powerful membranolytic effect and low potential for inducing resistance in bacteria. This peptide’s characteristics highlighted its potential as an alternative for combating infection caused by E. coli multiresistant bacteria and/or for designing new AMPs.

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Sun, Changbao, Yingying Li, Songsong Cao, Haimei Wang, Chenggang Jiang, Shiyue Pang, Muhammad Hussain, and Juncai Hou. "Antibacterial Activity and Mechanism of Action of Bovine Lactoferricin Derivatives with Symmetrical Amino Acid Sequences." International Journal of Molecular Sciences 19, no. 10 (September 27, 2018): 2951. http://dx.doi.org/10.3390/ijms19102951.

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In recent years, the overuse of antibiotics has become very serious. Many pathogenic bacteria have become resistant to them, with serious potential health consequences. Thus, it is urgent that we develop new antibiotic drugs. Antimicrobial peptides (AMPs) are important endogenous antibacterial molecules that contribute to immunity. Most have spectral antibacterial properties and do not confer drug resistance. In this paper, an 11-residue peptide (LFcinB18–28) with a sequence of KCRRWQWRMKK was modified by amino acid substitution to form a symmetrical amino acid sequence. The antibacterial activities and mechanisms of action of engineered peptides including KW-WK (KWRRWQWRRWK), FP-PF (FPRRWQWRRPF), FW-WF (FWRRWQWRRWF), and KK-KK (KKRRWQWRRKK) were investigated. The four engineered peptides could more effectively inhibit bacteria than the original peptide, LFcinB18–28. This suggested that a symmetrical amino acid sequence might enhance the antibacterial activity of AMPs. However, only peptides KW-WK, FP-PF, and KK-KK were safe; FW-WF displayed hemolytic activity. The engineered peptides shared cationic and amphipathic characteristics that facilitated interactions with the anionic microbial membranes, leading to disruption of membrane integrity and permeabilizing microbial membranes, resulting in cell death. Therefore, a symmetrical amino acid sequence and related structural parameters offer an alternative approach to the design of AMPs. This will provide a scientific basis for the design and synthesis of new AMPs.

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Hausmann, Stefan, Margarita Martin, Laurent Gauthier, and Kai W. Wucherpfennig. "Structural Features of Autoreactive TCR That Determine the Degree of Degeneracy in Peptide Recognition." Journal of Immunology 162, no. 1 (January 1, 1999): 338–44. http://dx.doi.org/10.4049/jimmunol.162.1.338.

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Abstract Structural aspects of human TCRs that allow the activation of autoreactive T cells by diverse microbial peptides were examined using two human myelin basic protein (MBP)-specific T cell clones. The TCR sequences of these clones differed only in the N region of TCR-α and -β since the clones had the same Vα-Jα and Vβ-Jβ rearrangements. The two clones had a similar fine specificity for the MBP peptide, except for the P5 position of the peptide (lysine). In the crystal structure of the HLA-DR2/MBP peptide complex, P5 lysine is a prominent, solvent-exposed residue in the center of the DR2/MBP peptide surface. Five microbial peptides with conservative or nonconservative changes at the P5 position (lysine to arginine, serine, or proline) activated one of these clones. In contrast, the other clone was activated only by three of these peptides which had a conservative lysine to arginine change at P5. The degree of specificity/degeneracy in recognition of the P5 side chain was the key difference between these TCRs since the Escherichia coli/Haemophilus influenzae peptide stimulated both clones when the P5 position was substituted from serine to arginine. These results demonstrate that the complementarity-determining region 3 loops contribute to the degree of degeneracy in peptide recognition by human MBP-specific TCRs.

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Russi, J. P., R. J. Wallace, and C. J. Newbold. "The influence of the pattern of peptide supply on microbial activity in the rumen simulating fermentor Rusitec." Proceedings of the British Society of Animal Science 2001 (2001): 28. http://dx.doi.org/10.1017/s1752756200004105.

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Peptides and to a lesser extent amino acids accumulate in rumen fluid in the early post feeding period and rapidly decline thereafter (Broderick & Wallace, 1988). Numerous studies have demonstrated benefits to feeding peptides, in terms of increased microbial growth in the rumen (Newbold, 1999). However, given that peptides will only be available in the rumen for a short time after feeding it may be necessary to match supply of peptides and energy in the rumen to maximise the stimulation in microbial activity. The objective of this study was thus to investigate if microbial protein synthesis in rumen fluid would be enhanced by a synchronous provision of peptides and energy.

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Maddah, Fayrouz El, Mamona Nazir, and Gabriele M. König. "The Rare Amino Acid Building Block 3-(3-furyl)-Alanine in the Formation of Non-ribosomal Peptides." Natural Product Communications 12, no. 1 (January 2017): 1934578X1701200. http://dx.doi.org/10.1177/1934578x1701200140.

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Microorganisms have made considerable contributions to the production of peptide secondary metabolites, many of them with therapeutic potential, e.g., the fungus-derived immunosuppressant cyclosporine A and the antibiotic daptomycin originating from Streptomyces. Most of the medically used peptides are the product of non-ribosomal peptide synthetases (NRPS), incorporating apart from proteinogenic also unique, non-proteinogenic amino acids into the peptides. An extremely rare such amino acid is 3-(3-furyl)-alanine. So far, only few peptides have been found that contain this residue, including the rhizonins, bingchamide B and endolides. The producer of the rhizonins was proven to be the bacterial endosymbiont Burkholderia endofungorum inside the fungus Rhizopus microsporus. The microbial origin, chemistry and bioactivity of the 3-(3-furyl)-alanine containing peptides are the focus of this review.

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Nelson, Ryan, and Marc Jenkins. "Implications of T cell receptor cross-reactivity on the CD4+ T cell repertoire (APP3P.111)." Journal of Immunology 194, no. 1_Supplement (May 1, 2015): 113.12. http://dx.doi.org/10.4049/jimmunol.194.supp.113.12.

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Abstract Naïve CD4+ T cell populations with T cell receptors (TCR) specific for different major histocompatibility complex II (MHCII)-bound foreign peptides vary in size for unknown reasons. Negative selection on self peptides could play a role. We found that MHCII-binding nonamer peptides only had to have the same residues at five positions to be recognized by the same TCR. This degree of TCR cross-reactivity between self and foreign peptides reduced the sizes of foreign peptide-specific T cell populations via clonal deletion. Small foreign p:MHCII-specific populations that underwent a greater degree of cross-reactive negative selection were on average lower affinity and produced more variable effector cell responses to immunization. In contrast, large foreign p:MHCII-specific T cell populations with minimal evidence of negative selection were higher affinity and produced larger responses to immunization. Reciprocally, an incompletely deleted naïve T cell population specific for a tissue-restricted self peptide could be triggered by similar microbial peptides to cause autoimmunity. Thus, TCR cross-reactivity between similar self and foreign peptides influences the size of certain foreign peptide-specific T cell populations, and may allow tissue-restricted self peptide-specific populations to cause autoimmunity after infection.

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Niemi, Liza Danielsson, and Ingegerd Johansson. "Salivary Statherin Peptide-Binding Epitopes of Commensal and Potentially Infectious Actinomyces spp. Delineated by a Hybrid Peptide Construct." Infection and Immunity 72, no. 2 (February 2004): 782–87. http://dx.doi.org/10.1128/iai.72.2.782-787.2004.

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ABSTRACT Adhesion of microorganisms to host receptor molecules such as salivary statherin molecules is a common event in oral microbial colonization. Here we used a hybrid peptide construct (with both a hydroxyapatite-binding portion and a test peptide portion) to map the interaction of Actinomyces species (and Candida albicans) with statherin. Adhesion to hybrid peptides and truncated statherin variants revealed three binding types, types I to III. (i) Type I strains of rat, hamster, and human infection origins bound C-terminal-derived QQYTF and PYQPQY peptides. The QQYTF peptide inhibited statherin binding for some strains but not for others. (ii) Type II strains of human and monkey tooth origins bound middle-region-derived YQPVPE and QPLYPQ peptides. Neither strain was inhibited by soluble peptides. (iii) Type III strains of human infection origins (and C. albicans) did not bind to either statherin-derived peptides or truncated statherin. Moreover, the type I strains inhibited by QQYTF were also inhibited by TF and QAATF peptides and were detached from statherin by the same peptides. In conclusion, it is suggested that commensal and potentially infectious microorganisms bind middle or C-terminal statherin differently and that other microbes might require discontinuous epitopes.

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Yang, Yu, Sabrina Schwiderek, Guido Grundmeier, and Adrian Keller. "Strain-Dependent Adsorption of Pseudomonas aeruginosa-Derived Adhesin-Like Peptides at Abiotic Surfaces." Micro 1, no. 1 (July 31, 2021): 129–39. http://dx.doi.org/10.3390/micro1010010.

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Implant-associated infections are an increasingly severe burden on healthcare systems worldwide and many research activities currently focus on inhibiting microbial colonization of biomedically relevant surfaces. To obtain molecular-level understanding of the involved processes and interactions, we investigate the adsorption of synthetic adhesin-like peptide sequences derived from the type IV pili of the Pseudomonas aeruginosa strains PAK and PAO at abiotic model surfaces, i.e., Au, SiO2, and oxidized Ti. These peptides correspond to the sequences of the receptor-binding domain 128–144 of the major pilin protein, which is known to facilitate P. aeruginosa adhesion at biotic and abiotic surfaces. Using quartz crystal microbalance with dissipation monitoring (QCM-D), we find that peptide adsorption is material- as well as strain-dependent. At the Au surface, PAO(128–144) shows drastically stronger adsorption than PAK(128–144), whereas adsorption of both peptides is markedly reduced at the oxide surfaces with less drastic differences between the two sequences. These observations suggest that peptide adsorption is influenced by not only the peptide sequence, but also peptide conformation. Our results furthermore highlight the importance of molecular-level investigations to understand and ultimately control microbial colonization of surfaces.

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Singh, D. P., T. Kikuchi, V. K. Singh, and T. Shinohara. "A single amino acid substitution in core residues of S-antigen prevents experimental autoimmune uveitis." Journal of Immunology 152, no. 9 (May 1, 1994): 4699–705. http://dx.doi.org/10.4049/jimmunol.152.9.4699.

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Abstract We have previously reported that microbial Ags, having a three- to six-amino-acid-sequence homology with a uveitopathogenic epitope (peptide M) of retinal soluble protein (S-Ag), induce experimental autoimmune uveitis (EAU). Another uveitopathogenic epitope (peptide G) of S-Ag also was characterized. In addition, we have characterized the core sequences by truncating peptides G and M from amino acid and carboxyl termini. In this study, we have further defined the core sequences using synthetic octapeptides with a single amino acid substitution. In addition, the analogues of peptides Gm5 or Mm4 are capable of inhibiting the proliferative response of T-lymphocytes from rats immunized with peptides G-8 or M-8, respectively. Co-injection of a pathogenic peptide with nonpathogenic substitution analogues blocked the induction of EAU. These results suggest that specific nonpathogenic analogues with single amino acid substitution derived from pathogenic peptides have potential for prevention and therapy of autoimmune diseases.

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Gu, Qiu-hua, Megan Huynh, Yue Shi, Xiao-yu Jia, Jie-jian Luo, Tai-jiao Jiang, Zhao Cui, Joshua D. Ooi, A. Richard Kitching, and Ming-hui Zhao. "Experimental Antiglomerular Basement Membrane GN Induced by a Peptide from Actinomyces." Journal of the American Society of Nephrology 31, no. 6 (May 22, 2020): 1282–95. http://dx.doi.org/10.1681/asn.2019060619.

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BackgroundAntiglomerular basement membrane (anti-GBM) disease is associated with HLA-DRB1*1501 (the major predisposing genetic factor in the disease), with α3127–148 as a nephritogenic T and B cell epitope. Although the cause of disease remains unclear, the association of infections with anti-GBM disease has been long suspected.MethodsTo investigate whether microbes might activate autoreactive T and B lymphocytes via molecular mimicry in anti-GBM disease, we used bioinformatic tools, including BLAST, SYFPEITHI, and ABCpred, for peptide searching and epitope prediction. We used sera from patients with anti-GBM disease to assess peptides recognized by antibodies, and immunized WKY rats and a humanized mouse model (HLA-DR15 transgenic mice) with each of the peptide candidates to assess pathogenicity.ResultsOn the basis of the critical motif, the bioinformatic approach identified 36 microbial peptides that mimic human α3127–148. Circulating antibodies in sera from patients with anti-GBM recognized nine of them. One peptide, B7, derived from Actinomyces species, induced proteinuria, linear IgG deposition on the GBM, and crescent formation when injected into WKY rats. The antibodies to B7 also targeted human and rat α3127–148. B7 induced T cell activation from human α3127–148-immunized rats. T cell responses to B7 were detected in rats immunized by Actinomyces lysate proteins or recombinant proteins. We confirmed B7’s pathogenicity in HLA-DR15 transgenic mice that developed kidney injury similar to that observed in α3135–145-immunized mice.ConclusionsSera from patients with anti-GBM disease recognized microbial peptides identified through a bioinformatic approach, and a peptide from Actinomyces induced experimental anti-GBM GN by T and B cell crossreactivity. These studies demonstrate that anti-GBM disease may be initiated by immunization with a microbial peptide.

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Ameen, Ayesha, and Shahid Raza. "Metaproteomics approaches and techniques: A review." International Journal of Advances in Scientific Research 3, no. 5 (June 5, 2017): 49. http://dx.doi.org/10.7439/ijasr.v3i5.4167.

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Extensive studies have been done on metagenomics for various microbial communities. The advancements in metagenomics level led to the need of metaproteomics approaches. Metaproteomics involve the identification, function and expression of various proteins present in microbial community, it also involves the identification and expression analysis of stress related proteins. The concepts of metaproteomics come with advancement in proteomics techniques which includes 2D gel electrophoresis for the identification of proteins and peptides in a particular microbial community. Mass spectrometry which is used to separate the proteins by desorption and ionization using a gas on a liquid medium. MALDI use for protein identification and separation, connected with TOF to give better results. The metaproteomics approaches become more advanced when HPLC and LC were used for peptides and protein with computational tools to sequence the peptide and protein. It is concluded that there is a requirement of research in metaproteomics. Many scientists have done research on these approaches but there is lack of better quality and desirable results.

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Nong, Nhung Thi Phuong, and Jue-Liang Hsu. "Bioactive Peptides: An Understanding from Current Screening Methodology." Processes 10, no. 6 (June 2, 2022): 1114. http://dx.doi.org/10.3390/pr10061114.

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Bioactive peptides with high potency against numerous human disorders have been regarded as a promising therapy in disease control. These peptides could be released from various dietary protein sources through hydrolysis processing using physical conditions, chemical agents, microbial fermentation, or enzymatic digestions. Considering the diversity of the original proteins and the complexity of the multiple structural peptides that existed in the hydrolysis mixture, the screening of bioactive peptides will be a challenge task. Well-organized and well-designed methods are necessarily required to enhance the efficiency of studying the potential peptides. This article, hence, provides an overview of bioactive peptides with an emphasis on the current strategy used for screening and characterization methods. Moreover, the understanding of the biological activities of peptides, mechanism inhibitions, and the interaction of the complex of peptide–enzyme is commonly evaluated using specific in vitro assays and molecular docking analysis.

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Luu, Dee Dee, Anna Joe, Yan Chen, Katarzyna Parys, Ofir Bahar, Rory Pruitt, Leanne Jade G. Chan, et al. "Biosynthesis and secretion of the microbial sulfated peptide RaxX and binding to the rice XA21 immune receptor." Proceedings of the National Academy of Sciences 116, no. 17 (April 4, 2019): 8525–34. http://dx.doi.org/10.1073/pnas.1818275116.

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The rice immune receptor XA21 is activated by the sulfated microbial peptide required for activation of XA21-mediated immunity X (RaxX) produced byXanthomonas oryzaepv.oryzae(Xoo). Mutational studies and targeted proteomics revealed that the RaxX precursor peptide (proRaxX) is processed and secreted by the protease/transporter RaxB, the function of which can be partially fulfilled by a noncognate peptidase-containing transporter component B (PctB). proRaxX is cleaved at a Gly–Gly motif, yielding a mature peptide that retains the necessary elements for RaxX function as an immunogen and host peptide hormone mimic. These results indicate that RaxX is a prokaryotic member of a previously unclassified and understudied group of eukaryotic tyrosine sulfated ribosomally synthesized, posttranslationally modified peptides (RiPPs). We further demonstrate that sulfated RaxX directly binds XA21 with high affinity. This work reveals a complete, previously uncharacterized biological process: bacterial RiPP biosynthesis, secretion, binding to a eukaryotic receptor, and triggering of a robust host immune response.

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Larder, Christina E., Michèle M. Iskandar, and Stan Kubow. "Dynamic Multi-Stage Gastrointestinal Digestion Model Assessment of Microbial Fermentation Products of Collagen Hydrolysates." Proceedings 61, no. 1 (October 30, 2020): 12. http://dx.doi.org/10.3390/iecn2020-06998.

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Proteins, peptides and amino acids (AAs) that bypass upper gastrointestinal (GI) digestion can be fermented in the colonic regions. This could lead to microbial production of health promoting short-chain fatty acids (SCFAs). Nitrogenous compounds can also be fermented to generate potentially harmful branched chain fatty acids (BCFAs). As collagen hydrolysate (CH) supplements contain a high peptide content, we evaluated whether peptides that undergo intestinal CH digestion and microbial fermentation can generate SCFAs and BCFAs. Two bovine-sourced CH formulations (CH-GL and CH-OPT) underwent digestive processes and microbial fermentation for 24 h in a dynamic GI digestion model containing human fecal matter. After 24 h, CH-OPT showed a significant (p < 0.05) increase in SCFAs (propionic, butyric and valeric acids) in the ascending colonic vessel with no changes observed with CH-GL. Only CH-OPT showed a significant (p < 0.05) increase in BCFAs, also noted in the ascending colon. No significant (p < 0.05) changes to SCFAs and BCFAs were observed in the transverse and descending colons for both CHs. These findings demonstrate that CHs can induce microbial production of SCFAs and BCFAs although this appears to depend on the CH tested. More studies are needed to determine the physiological significance of these microbial metabolites from intake of CH supplements.

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Kaul, Viraj, Shubhangi Warke, and Uma Tumlam. "Anti-microbial Peptides: New Weapon against Bacteria." International Journal of Current Microbiology and Applied Sciences, no. 9 (June 10, 2020): 2313–19. http://dx.doi.org/10.20546/ijcmas.2020.906.283.

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Pieters, Roland, Christopher Arnusch, and Eefjan Breukink. "Membrane Permeabilization by Multivalent Anti-Microbial Peptides." Protein & Peptide Letters 16, no. 7 (July 1, 2009): 736–42. http://dx.doi.org/10.2174/092986609788681841.

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Bulet, Philippe, Reto Stocklin, and Laure Menin. "Anti-microbial peptides: from invertebrates to vertebrates." Immunological Reviews 198, no. 1 (April 2004): 169–84. http://dx.doi.org/10.1111/j.0105-2896.2004.0124.x.

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Larrick, James W., Michimasa Hirata, Jian Zhong, and Susan C. Wright. "Anti-microbial activity of human CAP18 peptides." Immunotechnology 1, no. 1 (May 1995): 65–72. http://dx.doi.org/10.1016/1380-2933(95)00006-2.

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Javid, B., P. A. MacAry, W. Oehlmann, M. Singh, and P. J. Lehner. "Peptides complexed with the protein HSP70 generate efficient human cytolytic T-lymphocyte responses." Biochemical Society Transactions 32, no. 4 (August 1, 2004): 622–25. http://dx.doi.org/10.1042/bst0320622.

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Microbial HSPs (heat-shock proteins) are implicated in the induction of the innate and adaptive arms of the immune response. We set out to determine whether peptides complexed with HSP70 generate efficient CTL (cytolytic T-lymphocyte) responses. Human dendritic cells pulsed with peptide-loaded microbial HSP70 complexes generate potent antigen-specific CTL responses. Using fluorescence anisotropy, we have calculated the peptide-binding affinity of mycobacterial HSP70 (KD=14 μM) and show that 120 pM HSP70-bound peptide is sufficient to generate a peptide-specific CTL response that is four orders of magnitude more efficient than the peptide alone. Through the generation of mycobacterial HSP70 truncations, we find that the minimal 136 amino acid, mycobacterial HSP70 peptide-binding domain is sufficient to generate CTL responses. The design of an HSP70 mutant, in which the peptide-binding site of HSP70 is filled with a bulky hydrophobic residue, leads to a large decrease in the peptide-binding affinity. This mutant HSP70 retains stimulatory capacity but is unable to generate CTL and has separated antigen delivery from immunostimulation of dendritic cells.

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Przybylski, Rémi, Laurent Bazinet, Loubna Firdaous, Mostafa Kouach, Jean-François Goossens, Pascal Dhulster, and Naïma Nedjar-Arroume. "Electroseparation of Slaughterhouse By-Product: Antimicrobial Peptide Enrichment by pH Modification." Membranes 10, no. 5 (May 3, 2020): 90. http://dx.doi.org/10.3390/membranes10050090.

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The fractionation of bioactive peptides from hydrolysate is a main challenge to produce efficient alternative for synthetic additives. In this work, electrodialysis with ultrafiltration membrane (EDUF) was proposed to increase the purity of one antimicrobial peptide from slaughterhouse by-product hydrolysate. This targeted-peptide, α137–141 (653 Da, TSKYR), inhibits a large spectrum of microbial growths and delays meat rancidity; therefore, if concentrated, it could be used as food antimicrobial. In this context, three pH values were investigated during EDUF treatment to increase the α137–141 purity: 4.7, 6.5, and 9. pH 9 showed the highest purity increase—75-fold compared to the initial hydrolysate. Although the whole hydrolysate contains more than 100 peptides, only six peptides were recovered at a significant concentration. In this fraction, the α137–141 peptide represented more than 50% of the recovered total peptide concentration. The EDUF α137–141-enriched fraction obtained in this optimized condition would be a promising natural preservative to substitute synthetic additives used to protect food.

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Cardoso, Priscila, Hugh Glossop, Thomas G. Meikle, Arturo Aburto-Medina, Charlotte E. Conn, Vijayalekshmi Sarojini, and Celine Valery. "Molecular engineering of antimicrobial peptides: microbial targets, peptide motifs and translation opportunities." Biophysical Reviews 13, no. 1 (January 21, 2021): 35–69. http://dx.doi.org/10.1007/s12551-021-00784-y.

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Botelho, Cláudia M., Pedro Ferreira-Santos, Duarte Toubarro, Hugo Dinis, Hugo Osório, Augusto Costa-Barbosa, Paula Sampaio, Nelson Simões, and José A. Teixeira. "Chicken Feather Keratin Peptides for the Control of Keratinocyte Migration." Applied Sciences 11, no. 15 (July 23, 2021): 6779. http://dx.doi.org/10.3390/app11156779.

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FAO estimates that in 2030 the poultry meat production could reach 120 million tons, which is a challenge in terms of waste management. Feathers are mainly composed of keratin, an important biomaterial. Using feathers as a source of keratin will minimize the waste generated, while contributing to supply an important material for several industries, such as pharmaceutical and biomedical. The peptides were extracted from the feathers by microbial degradation. In this study, we evaluated the peptides effect on keratinocyte metabolic activity and migration. The influence of these peptides on non-activated and activated macrophages was also assessed. It was demonstrated that depending on the keratin peptide fraction in contact with keratinocytes, it is possible to modulate the migration rate of the keratinocytes. Peptide fraction with low molecular weight increases migration, while peptides with a high range of molecular sizes decreases it. Some peptide fractions induce the secretion of TNF-α in non-activated macrophages and not on activated macrophages, demonstrating that these peptides should only be placed in contact with cells, in the context of an ongoing inflammatory process. This work is a step forward on the understanding of keratin peptides influence on keratinocytes and immune cells system cells, macrophages.

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Solieri, Lisa, Andrea Baldaccini, Serena Martini, Aldo Bianchi, Valentina Pizzamiglio, and Davide Tagliazucchi. "Peptide Profiling and Biological Activities of 12-Month Ripened Parmigiano Reggiano Cheese." Biology 9, no. 7 (July 16, 2020): 170. http://dx.doi.org/10.3390/biology9070170.

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Proteolysis degree, biological activities, and water-soluble peptide patterns were evaluated in 12 month-ripened Parmigiano Reggiano (PR) cheeses collected in different dairy farms and showing different salt and fat content. Samples classified in high-salt and high-fat group (HH) generally showed lower proteolysis degree than samples having low-salt and low-fat content (LL). This positive correlation between salt/fat reduction and proteolysis was also confirmed by the analysis of biological activities, as the LL group showed higher average values of angiotensin-converting enzyme (ACE)-inhibitory and antioxidant activities. UHPLC/HR-MS allowed the identification of 805 unique peptides: LL and HH groups shared 59.3% of these peptides, while 20.9% and 19.9% were LL and HH specific, respectively. Frequency analysis of peptides identified a core of 183 peptides typical of 12-month ripened PR cheeses (corresponding to the 22.7% of total peptides), but no significant differences were detected in peptide patterns between LL and HH groups. Forty bioactive peptides, including 18 ACE-inhibitors and 12 anti-microbial peptides, were identified, of which 25 firstly found in PR cheese. Globally, this work contributed to unraveling the potentially healthy benefits of peptides fraction in PR cheese and provided prior evidence that PR with reduced fat/salt content showed the highest antihypertensive and antioxidant activities.

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Zinina, O., O. Neverova, P. Sharaviev, E. Neverova, and E. Aleksandrina. "Determination of the functional properties of protein hydrolysates by the in silico method." E3S Web of Conferences 395 (2023): 03004. http://dx.doi.org/10.1051/e3sconf/202339503004.

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Bioactive peptides are of increasing interest to scientists. The development of peptidomics and bioinformatics contributes to a deeper study of peptides obtained by enzymatic hydrolysis of raw materials. In this work, the in silico method was used to study the properties and biological value of peptides identified in protein hydrolysates obtained by microbial fermentation of the broiler chicken gizzards in whey with the addition of bifidobacteria and propionic acid bacteria. The activity of the peptides was determined using the BIOPEP database. Potential toxicity and such properties as hydrophobicity, hydropathicity, hydrophilicity, molecular weight of each peptide were predicted through the tool ToxinPred. The potential activity of the peptides was evaluated using the PeptideRanker database. The conducted studies made it possible to identify bioactive peptides TR, SY, VW, PPP, SW in hydrolysates, which have various physiological effects. Several peptides with high potential biological activity have also been identified. Due to the fact that not all peptides obtained during the fermentation of raw materials have been studied, in silico methods allow us to assess the feasibility of isolating certain peptides from hydrolysates.

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Serba, Elena, Liubov Rimareva, Marina Overchenko, Nadezhda Ignatova, Polina Tadzhibova, and Sergey Zorin. "Production of peptides and amino acids from microbial biomass in food and feed industries: biotechnological aspects." Foods and Raw Materials 8, no. 2 (September 30, 2020): 268–76. http://dx.doi.org/10.21603/2308-4057-2020-2-268-276.

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Introduction. Microbial biomass is a popular source of food ingredients and feed additives. Its high use has made it focus of many relevant studies. Yeast and fungal biomasses proved to be useful substrates that improve the quality and biological value of functional products. They differ in the content and composition of proteins and polysaccharides. The present research dealt with the enzymatic decomposition of proteins found in a novel fungal and yeast biomass. The research objective was to describe the peptide and amino acid composition of their enzymatic hydrolysates. Study objects and methods. The research featured a new fungal and yeast biomass mix. Aspergillus oryzae is a mycelial fungus and a popular industrial producer of hydrolytic enzymes in food industry. As for the yeast, it was the Saccharomyces cerevisiae strain, which is often used in baking. Results and discussion. The total content of identified amino acids in the fungal and yeast biomass was 306.0 mg/g, which was 1.5 times higher than in the fungal biomass alone. The biomass mix demonstrated a higher biological value of proteins than the yeast biomass. A set of experiments made it possible to compile a scheme for the biocatalytic destruction of polymers in the fungal and yeast biomass under the effect of fungal intracellular and endogenous enzymes. The article also contains a thorough description of the obtained enzymatic hydrolysates with various fractional compositions of peptides and free amino acids. Peptides with the molecular weight in the range of up to 29.0 kDa decreased by 2.1 times after 5 h of hydrolysis and by 10.7 times after 18 h. The designed conditions doubled the release of amino acids and increased the content of low-molecular-weight peptides up to 75.3%. Conclusion. The research provided a new algorithm for the biocatalytic conversion of microbial biomass. Regulating the conditions of enzymatic hydrolysis made it possible to obtain enzymatic hydrolysates with a desired degree of protein degradation. They could serve as peptides and amino acids in functional food and feed products.

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Endres, Kristina. "Amyloidogenic Peptides in Human Neuro-Degenerative Diseases and in Microorganisms: A Sorrow Shared Is a Sorrow Halved?" Molecules 25, no. 4 (February 19, 2020): 925. http://dx.doi.org/10.3390/molecules25040925.

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The term “amyloid” refers to proteinaceous deposits of peptides that might be generated from larger precursor proteins e.g., by proteolysis. Common to these peptides is a stable cross-β dominated secondary structure which allows self-assembly, leading to insoluble oligomers and lastly to fibrils. These highly ordered protein aggregates have been, for a long time, mainly associated with human neurodegenerative diseases such as Alzheimer’s disease (Amyloid-β peptides). However, they also exert physiological functions such as in release of deposited hormones in human beings. In the light of the rediscovery of our microbial commensals as important companions in health and disease, the fact that microbes also possess amyloidogenic peptides is intriguing. Transmission of amyloids by iatrogenic means or by consumption of contaminated meat from diseased animals is a well-known fact. What if also our microbial commensals might drive human amyloidosis or suffer from our aggregated amyloids? Moreover, as the microbial amyloids are evolutionarily older, we might learn from these organisms how to cope with the sword of Damocles forged of endogenous, potentially toxic peptides. This review summarizes knowledge about the interplay between human amyloids involved in neurodegenerative diseases and microbial amyloids.

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Ranilla, M. J., M. D. Carro, S. López, C. J. Newbold, and R. J. Wallace. "Influence of nitrogen source on the fermentation of fibre from barley straw and sugarbeet pulp by ruminal micro-organismsin vitro." British Journal of Nutrition 86, no. 6 (December 2001): 717–24. http://dx.doi.org/10.1079/bjn2001475.

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Incubations were carried out with a batch culture system to study the effects of different N sources on the fermentation by ruminal micro-organisms from Merino sheep of two fibre substrates derived from feedstuffs that differed in their fermentation rate. The substrates were neutral-detergent fibre (NDF) from barley straw and sugarbeet pulp. N sources were ammonia (NH4Cl) and peptides (Trypticase). Three treatments were made by replacing ammonia-N with peptide-N at levels of 0 (AMMO), 33 (PEPLOW) and 66 % (PEPHIGH) of total N. There were no differences (P>0·05) between treatments in NDF degradation for both the barley straw and the sugarbeet pulp. Peptides increased (P<0·05) total volatile fatty acids daily production for both substrates, with greater values (P<0·001) for PEPHIGH than for PEPLOW for the sugarbeet pulp. The presence of peptides also increased (P<0·05) microbial N synthesis compared with AMMO, with PEPHIGH supporting more growth (P<0·001) than PEPLOW when the sugarbeet pulp NDF was fermented. The presence of peptides increased (P<0·01) the amount of solids-associated micro-organisms (SAM)-N for both the barley straw and the sugarbeet pulp fibres, values in the PEPHIGH treatment being higher (P<0·001) than those in PEPLOW. The proportion of SAM-N in the total microbial N was not affected (P>0·05) by the presence of peptides compared with the AMMO treatment, but values were greater for the PEPHIGH compared with the PEPLOW N source, reaching statistical significance (P<0·05) only for the sugarbeet pulp. For liquid-associated micro-organisms, the AMMO treatment resulted in the greatest (P<0·05) proportion of N derived from ammonia for both substrates, with a further decrease (P<0·01) for the PEPHIGH treatment compared with the PEPLOW for the sugarbeet pulp, indicating preferential uptake of peptides when they were available. Microbial growth efficiency (g microbial N/kg NDF degraded) was not affected (P>0·05) by N source. These results indicate that N forms other than ammonia are needed for maximal growth of fibre-digesting ruminal micro-organisms.

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Zemanová, Jana, and Květoslava Šustová. "The Problem of Bitter Peptides Formed in the Process of Cheese Ripening." Chemické listy 117, no. 5 (May 15, 2023): 301–7. http://dx.doi.org/10.54779/chl20230301.

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Bitter peptides are formed by the breakdown of proteins and high-molecular peptides during proteolysis. Their formation in cheeses is related to the proteolytic activity of rennet in balance with the peptidase activity of microbial enzymes of lactic acid bacteria. The bitter taste then arises when there is a disproportion between the formation and degradation of bitter peptides by increasing their concentration above the perception threshold. The extent to which bitter peptides affect the overall taste of cheese depends on the balance between their formation and breakdown to non-bitter lower peptides and amino acids. Only a perfectly balanced proteolysis process enables the creation of quality matured cheese with a characteristic taste and aroma. Therefore, a complete clarification of the mechanism is desirable, and thus also the possibility of control and regulation of this process.

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Vo, Tien Duy, Christoph Spahn, Mike Heilemann, and Helge B. Bode. "Microbial Cationic Peptides as a Natural Defense Mechanism against Insect Antimicrobial Peptides." ACS Chemical Biology 16, no. 3 (February 17, 2021): 447–51. http://dx.doi.org/10.1021/acschembio.0c00794.

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Wallace, R. J. "Influence of acetylation on peptide breakdown by microorganisms from the sheep rumen." Proceedings of the British Society of Animal Production (1972) 1991 (March 1991): 46. http://dx.doi.org/10.1017/s0308229600019978.

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Protein is broken down by rumen microorganisms via peptides and amino acids to produce ammonia at rates which frequently exceed microbial requirements for N. Much of the ammonia-N formed in this way is eventually excreted as urea. If any of the steps in the degradation sequence could be inhibited, excessive ammonia production would be reduced. More protein, peptides or amino acids would escape fermentation in the rumen, thereby improving the protein nutrition of the host animal.The breakdown of peptides to amino acids is a central part of the degradation sequence. The main enzymic mechanism by which peptides are hydrolysed in the rumen is a bacterial dipeptidyl aminopeptidase, which cleaves dipeptides from the N-terminus of the peptide chain (Wallace & McKain, 1990). Little carboxypeptidase activity appears to be present. The present experiments were undertaken to find out to what extent blocking the N-terminus of peptides enables them to survive degradation in rumen fluid, and to determine which peptides can be protected in this way.

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Bhopale, Girish M. "Antimicrobial Peptides: A Promising Avenue for Human Healthcare." Current Pharmaceutical Biotechnology 21, no. 2 (February 12, 2020): 90–96. http://dx.doi.org/10.2174/1389201020666191011121722.

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Antimicrobial drugs resistant microbes have been observed worldwide and therefore alternative development of antimicrobial peptides has gained interest in human healthcare. Enormous progress has been made in the development of antimicrobial peptide during the last decade due to major advantages of AMPs such as broad-spectrum activity and low levels of induced resistance over the current antimicrobial agents. This review briefly provides various categories of AMP, their physicochemical properties and mechanism of action which governs their penetration into microbial cell. Further, the recent information on current status of antimicrobial peptide development, their applications and perspective in human healthcare are also described.

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Casciaro, Bruno, Floriana Cappiello, Maria Rosa Loffredo, Francesca Ghirga, and Maria Luisa Mangoni. "The Potential of Frog Skin Peptides for Anti-Infective Therapies: The Case of Esculentin-1a(1-21)NH2." Current Medicinal Chemistry 27, no. 9 (March 27, 2020): 1405–19. http://dx.doi.org/10.2174/0929867326666190722095408.

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Antimicrobial Peptides (AMPs) are the key effectors of the innate immunity and represent promising molecules for the development of new antibacterial drugs. However, to achieve this goal, some problems need to be overcome: (i) the cytotoxic effects at high concentrations; (ii) the poor biostability and (iii) the difficulty in reaching the target site. Frog skin is one of the richest natural storehouses of AMPs, and over the years, many peptides have been isolated from it, characterized and classified into several families encompassing temporins, brevinins, nigrocins and esculentins. In this review, we summarized how the isolation/characterization of peptides belonging to the esculentin-1 family drove us to the design of an analogue, i.e. esculentin-1a(1-21)NH2, with a powerful antimicrobial action and immunomodulatory properties. The peptide had a wide spectrum of activity, especially against the opportunistic Gram-negative bacterium Pseudomonas aeruginosa. We described the structural features and the in vitro/in vivo biological characterization of this peptide as well as the strategies used to improve its biological properties. Among them: (i) the design of a diastereomer carrying Damino acids in order to reduce the peptide’s cytotoxicity and improve its half-life; (ii) the covalent conjugation of the peptide to gold nanoparticles or its encapsulation into poly(lactide- co-glycolide) nanoparticles; and (iii) the peptide immobilization to biomedical devices (such as silicon hydrogel contact lenses) to obtain an antibacterial surface able to reduce microbial growth and attachment. Summing up the best results obtained so far, this review traces all the steps that led these frog-skin AMPs to the direction of peptide-based drugs for clinical use.

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Russi, Juan P., R. John Wallace, and C. James Newbold. "Influence of the pattern of peptide supply on microbial activity in the rumen simulating fermenter (RUSITEC)." British Journal of Nutrition 88, no. 1 (July 2002): 73–80. http://dx.doi.org/10.1079/bjn2002585.

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The source and pattern of N supply was varied in the rumen simulation technique (RUSITEC) in order to determine if continuous, rather than transient, availability of peptides was required for optimum ruminal fermentation. The energy source was fibre prepared from sugar-beet pulp. N was added as NH3continuously infused (AC) or peptides (Bacto®Casitone, a pancreatic hydrolysate of casein; Difco Laboratories, Detroit, MI, USA) continuously infused (PC) or added as a single dose at the time of feeding (PS). Free peptides were detected in the fermenter liquid for 4 h after feeding in the AC treatment, for 10 h in the PS treatment, and at all times with the PC treatment. Treatments had no effect on DM degradation. Approximately 40 % of the degradation occurred during the time no peptides were detected in the PS treatment. Microbial N flow tended to be higher with the peptide additions (P<0·061), with no significant difference between the two peptides treatments. The production of liquid-associated micro-organisms (LAM) was higher in the PC treatment (P<0·05) and the proportion of LAM derived from NH3lower (P<0·05). However, LAM only accounted for 20–30 % total microbial population. Our main conclusion was that peptides had a small stimulatory effect on the fermentation, but there was no indication that synchrony of supply of energy and amino acid-N in the fermenter promoted a more efficient fermentation than non-synchronous supply. This conclusion must be qualified, however, because some N remained in the fibre and may have become available progressively as the fibre was digested by the micro-organisms.

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HETRU, Charles, Lucienne LETELLIER, Ziv OREN, Jules A. HOFFMANN, and Yechiel SHAI. "Androctonin, a hydrophilic disulphide-bridged non-haemolytic anti-microbial peptide: a plausible mode of action." Biochemical Journal 345, no. 3 (January 25, 2000): 653–64. http://dx.doi.org/10.1042/bj3450653.

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Androctonin is a 25-residue non-haemolytic anti-microbial peptide isolated from the scorpion Androctonus australis and contains two disulphide bridges. Androctonin is different from known native anti-microbial peptides, being a relatively hydrophilic and non-amphipathic molecule. This raises the possibility that the target of androctonin might not be the bacterial membrane, shown to be a target for most amphipathic lytic peptides. To shed light on its mode of action on bacteria and its non-haemolytic activity, we synthesized androctonin, its fluorescent derivatives and its all-D-amino acid enantiomer. The enantiomer preserved high activity, suggesting a lipid-peptide interaction between androctonin and bacterial membranes. In Gram-positive and (at higher concentrations) Gram-negative bacteria, androctonin induced an immediate perturbation of the permeability properties of the cytoplasmic membrane of the bacterial energetic state, concomitant with perturbation of the morphology of the cell envelope as revealed by electron microscopy. Androctonin binds only to negatively charged lipid vesicles and induces the leakage of markers at high concentrations and with a slow kinetics, in contrast with amphipathic α-helical anti-microbial peptides that bind and permeate negatively charged vesicles, and to a smaller extent also zwitterionic ones. This might explain the selective lytic activity of androctonin towards bacteria but not red blood cells. Polarized attenuated total reflection-Fourier transform infrared spectroscopy revealed that androctonin adopts a β-sheet structure in membranes and did not affect the lipid acyl chain order, which supports a detergent-like effect. The small size of androctonin, its hydrophilic character and its physicochemical properties are favourable features for its potential application as a replacement for commercially available antibiotics to which bacteria have developed resistance.

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Rojas, Verónica, Luis Rivas, Constanza Cárdenas, and Fanny Guzmán. "Cyanobacteria and Eukaryotic Microalgae as Emerging Sources of Antibacterial Peptides." Molecules 25, no. 24 (December 9, 2020): 5804. http://dx.doi.org/10.3390/molecules25245804.

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Cyanobacteria and microalgae are oxygen-producing photosynthetic unicellular organisms encompassing a great diversity of species, which are able to grow under all types of extreme environments and exposed to a wide variety of predators and microbial pathogens. The antibacterial compounds described for these organisms include alkaloids, fatty acids, indoles, macrolides, peptides, phenols, pigments and terpenes, among others. This review presents an overview of antibacterial peptides isolated from cyanobacteria and microalgae, as well as their synergism and mechanisms of action described so far. Antibacterial cyanopeptides belong to different orders, but mainly from Oscillatoriales and Nostocales. Cyanopeptides have different structures but are mainly cyclic peptides. This vast peptide repertoire includes ribosomal and abundant non-ribosomal peptides, evaluated by standard conventional methodologies against pathogenic Gram-negative and Gram-positive bacteria. The antibacterial activity described for microalgal peptides is considerably scarcer, and limited to protein hydrolysates from two Chlorella species, and few peptides from Tetraselmis suecica. Despite the promising applications of antibacterial peptides and the importance of searching for new natural sources of antibiotics, limitations still persist for their pharmaceutical applications.

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Carrizosa, Ana M., Lindsay B. Nicholson, Michael Farzan, Scott Southwood, Alessandro Sette, Raymond A. Sobel, and Vijay K. Kuchroo. "Expansion by Self Antigen Is Necessary for the Induction of Experimental Autoimmune Encephalomyelitis by T Cells Primed with a Cross-Reactive Environmental Antigen." Journal of Immunology 161, no. 7 (October 1, 1998): 3307–14. http://dx.doi.org/10.4049/jimmunol.161.7.3307.

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Abstract Cross-reactivity with environmental antigens has been postulated as a mechanism responsible for the induction of autoimmune disease. Experimental autoimmune encephalomyelitis is a T cell-mediated autoimmune disease model inducible in susceptible strains of laboratory animals by immunization with protein constituents of myelin. We used myelin proteolipid protein (PLP) peptide 139–151 and its analogues to define motifs to search a protein database for structural homologues of PLP139–151 and identified five peptides derived from microbial Ags that elicit immune responses that cross-react with this self peptide. Exposure of naive SJL mice to the cross-reactive environmental peptides alone was insufficient to induce autoimmune disease even when animals were treated with Ag-nonspecific stimuli (superantigen or LPS). However, immunization of SJL mice with suboptimal doses of PLP139–151 after priming with cross-reactive environmental peptides consistently induced experimental autoimmune encephalomyelitis. Furthermore, T cell lines from mice immunized with cross-reactive environmental peptides and restimulated in vitro with PLP139–151 could induce disease upon transfer into naive recipients. These data suggest that expansion by self Ag is required to break the threshold to autoimmune disease in animals primed with cross-reactive peptides.

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Journal articles on the topic 'Microbial peptides'

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