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1
Lai, Zon W., Agnese Petrera et Oliver Schilling. « Protein amino-terminal modifications and proteomic approaches for N-terminal profiling ». Current Opinion in Chemical Biology 24 (février 2015) : 71–79. http://dx.doi.org/10.1016/j.cbpa.2014.10.026.
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Voronina, A. I., Yu V. Miroshnichenko et V. S. Skvortsov. « Bioinformatic identification of proteins with altered PTM levels in a mouse line established to study the mechanisms of the development of fibromuscular dysplasia ». Biomeditsinskaya Khimiya 70, no 4 (2024) : 248–55. http://dx.doi.org/10.18097/pbmc20247004248.
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Data from a mass spectrometry experiment of a mouse line developed to study the mechanisms of fibromuscular dysplasia and deposited by d'Escamard et al. in ProteomeXchange (PXD051750) have been analyzed. Identification of peptides with post-translational modifications (PTMs) was repeated using more stringent conditions than in the original work. The following modifications were considered during analysis of changes in the PTM levels in experimental and control groups of mice: acetylation of lysine residue and N-terminal protein peptide, ubiquitination of lysine residue, phosphorylation of serine, threonine and tyrosine residues, and deamination of asparagine and glutamine residues. The multistage analysis resulted in selection of 23 proteins with PTMs for which different levels of modification between experimental and control groups could be assumed. These included six proteins with N-terminal protein acetylation, which were particularly interesting: P80318 (T-complex protein 1 subunit gamma), P43274 (Histone H1.4), P97823 (Acyl-protein thioesterase 1), P63242 (Eukaryotic translation initiation factor 5A-1), Q3UMT1 (Protein phosphatase 1 regulatory subunit 12C), Q9D8Y0 (EF-hand domain-containing protein D2). Thus, repeated bioinformatic analysis of the data deposited in the specialized databases resulted in detection of changes in the level of N-terminal acetylation of proteins that might be functionally significant in the mechanisms underlying the development of fibromuscular dysplasia.
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Yu, Guann-Yi, Ki-Jeong Lee, Lu Gao et Michael M. C. Lai. « Palmitoylation and Polymerization of Hepatitis C Virus NS4B Protein ». Journal of Virology 80, no 12 (15 juin 2006) : 6013–23. http://dx.doi.org/10.1128/jvi.00053-06.
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ABSTRACT Hepatitis C Virus (HCV) NS4B protein induces a specialized membrane structure which may serve as the replication platform for HCV RNA replication. In the present study, we demonstrated that NS4B has lipid modifications (palmitoylation) on two cysteine residues (cysteines 257 and 261) at the C-terminal end. Site-specific mutagenesis of these cysteine residues on individual NS4B proteins and on an HCV subgenomic replicon showed that the lipid modifications, particularly of Cys261, are important for protein-protein interaction in the formation of the HCV RNA replication complex. We further demonstrated that NS4B can undergo polymerization. The main polymerization determinants were mapped in the N-terminal cytosolic domain of NS4B protein; however, the lipid modifications on the C terminus also facilitate the polymerization process. The lipid modification and the polymerization activity could be two properties of NS4B important for its induction of the specialized membrane structure involved in viral RNA replication.
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Dissmeyer, Nico. « Conditional Protein Function via N-Degron Pathway–Mediated Proteostasis in Stress Physiology ». Annual Review of Plant Biology 70, no 1 (29 avril 2019) : 83–117. http://dx.doi.org/10.1146/annurev-arplant-050718-095937.
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The N-degron pathway, formerly the N-end rule pathway, regulates functions of regulatory proteins. It impacts protein half-life and therefore directs the actual presence of target proteins in the cell. The current concept holds that the N-degron pathway depends on the identity of the amino (N)-terminal amino acid and many other factors, such as the follow-up sequence at the N terminus, conformation, flexibility, and protein localization. It is evolutionarily conserved throughout the kingdoms. One possible entry point for substrates of the N-degron pathway is oxidation of N-terminal Cys residues. Oxidation of N-terminal Cys is decisive for further enzymatic modification of various neo–N termini by arginylation that generates potentially neofunctionalized or instable proteoforms. Here, I focus on the posttranslational modifications that are encompassed by protein degradation via the Cys/Arg branch of the N-degron pathway—part of the PROTEOLYSIS 6 (PRT6)/N-degron pathway—as well as the underlying physiological principles of this branch and its biological significance in stress response.
5
Meinnel, Thierry, et Carmela Giglione. « Tools for analyzing and predicting N-terminal protein modifications ». PROTEOMICS 8, no 4 (février 2008) : 626–49. http://dx.doi.org/10.1002/pmic.200700592.
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Rose, K., P. O. Regamey, R. Anderegg, T. N. C. Wells et A. E. I. Proudfoot. « Human interleukin-5 expressed in Escherichia coli has N-terminal modifications ». Biochemical Journal 286, no 3 (15 septembre 1992) : 825–28. http://dx.doi.org/10.1042/bj2860825.
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Recombinant human interleukin-5 exists as four major isoforms all possessing N-terminal methionine. Peptide mapping and subsequent analysis by fast-atom-bombardment mass spectrometry (f.a.b.-m.s.) have shown that N-terminal modifications are the cause of the charge heterogeneity. In order of decreasing abundance, these are unmodified methionine, retention of N-terminal formyl group, oxidation of N-terminal methionine to sulphoxide and carbamoylation of the N-terminus. These results were confirmed by analysis of the reduced and alkylated intact protein by electrospray-ionization mass spectrometry. The implications of these findings for the production and characterization of recombinant proteins are briefly discussed.
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Lee, Seon Hwa, et Tomoyuki Oe. « Oxidative stress-mediated N-terminal protein modifications and MS-based approaches for N-terminal proteomics ». Drug Metabolism and Pharmacokinetics 31, no 1 (février 2016) : 27–34. http://dx.doi.org/10.1016/j.dmpk.2015.12.002.
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Ouidir, Tassadit, Frédérique Jarnier, Pascal Cosette, Thierry Jouenne et Julie Hardouin. « Characterization of N-terminal protein modifications in Pseudomonas aeruginosa PA14 ». Journal of Proteomics 114 (janvier 2015) : 214–25. http://dx.doi.org/10.1016/j.jprot.2014.11.006.
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Giglione, Carmela, Sonia Fieulaine et Thierry Meinnel. « N-terminal protein modifications : Bringing back into play the ribosome ». Biochimie 114 (juillet 2015) : 134–46. http://dx.doi.org/10.1016/j.biochi.2014.11.008.
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Van Damme, Petra. « Charting the N-Terminal Acetylome : A Comprehensive Map of Human NatA Substrates ». International Journal of Molecular Sciences 22, no 19 (2 octobre 2021) : 10692. http://dx.doi.org/10.3390/ijms221910692.
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N-terminal acetylation (Nt-acetylation) catalyzed by conserved N-terminal acetyltransferases or NATs embodies a modification with one of the highest stoichiometries reported for eukaryotic protein modifications to date. Comprising the catalytic N-alpha acetyltransferase (NAA) subunit NAA10 plus the ribosome anchoring regulatory subunit NAA15, NatA represents the major acetyltransferase complex with up to 50% of all mammalian proteins representing potential substrates. Largely in consequence of the essential nature of NatA and its high enzymatic activity, its experimentally confirmed mammalian substrate repertoire remained poorly charted. In this study, human NatA knockdown conditions achieving near complete depletion of NAA10 and NAA15 expression resulted in lowered Nt-acetylation of over 25% out of all putative NatA targets identified, representing an up to 10-fold increase in the reported number of substrate N-termini affected upon human NatA perturbation. Besides pointing to less efficient NatA substrates being prime targets, several putative NatE substrates were shown to be affected upon human NatA knockdown. Intriguingly, next to a lowered expression of ribosomal proteins and proteins constituting the eukaryotic 48S preinitiation complex, steady-state levels of protein N-termini additionally point to NatA Nt-acetylation deficiency directly impacting protein stability of knockdown affected targets.
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Millar, A. Harvey, Joshua L. Heazlewood, Carmela Giglione, Michael J. Holdsworth, Andreas Bachmair et Waltraud X. Schulze. « The Scope, Functions, and Dynamics of Posttranslational Protein Modifications ». Annual Review of Plant Biology 70, no 1 (29 avril 2019) : 119–51. http://dx.doi.org/10.1146/annurev-arplant-050718-100211.
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Assessing posttranslational modification (PTM) patterns within protein molecules and reading their functional implications present grand challenges for plant biology. We combine four perspectives on PTMs and their roles by considering five classes of PTMs as examples of the broader context of PTMs. These include modifications of the N terminus, glycosylation, phosphorylation, oxidation, and N-terminal and protein modifiers linked to protein degradation. We consider the spatial distribution of PTMs, the subcellular distribution of modifying enzymes, and their targets throughout the cell, and we outline the complexity of compartmentation in understanding of PTM function. We also consider PTMs temporally in the context of the lifetime of a protein molecule and the need for different PTMs for assembly, localization, function, and degradation. Finally, we consider the combined action of PTMs on the same proteins, their interactions, and the challenge ahead of integrating PTMs into an understanding of protein function in plants.
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Nassiri Toosi, Zahra, Xinya Su, Ruth Austin, Shilpa Choudhury, Wei Li, Yui Tik Pang, James C. Gumbart et Matthew P. Torres. « Combinatorial phosphorylation modulates the structure and function of the G protein γ subunit in yeast ». Science Signaling 14, no 688 (22 juin 2021) : eabd2464. http://dx.doi.org/10.1126/scisignal.abd2464.
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Intrinsically disordered regions (IDRs) in proteins are often targets of combinatorial posttranslational modifications, which serve to regulate protein structure and function. Emerging evidence suggests that the N-terminal tails of G protein γ subunits, which are essential components of heterotrimeric G proteins, are intrinsically disordered, phosphorylation-dependent determinants of G protein signaling. Here, we found that the yeast Gγ subunit Ste18 underwent combinatorial, multisite phosphorylation events within its N-terminal IDR. G protein–coupled receptor (GPCR) activation and osmotic stress induced phosphorylation at Ser7, whereas glucose and acid stress induced phosphorylation at Ser3, which was a quantitative indicator of intracellular pH. Each site was phosphorylated by a distinct set of kinases, and phosphorylation of one site affected phosphorylation of the other, as determined through exposure to serial stimuli and through phosphosite mutagenesis. Last, we showed that phosphorylation resulted in changes in IDR structure and that different combinations of phosphorylation events modulated the activation rate and amplitude of the downstream mitogen-activated protein kinase Fus3. These data place Gγ subunits among intrinsically disordered proteins that undergo combinatorial posttranslational modifications that govern signaling pathway output.
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Brettrager, Segura et van Waardenburg. « Tyrosyl-DNA Phosphodiesterase I N-Terminal Domain Modifications and Interactions Regulate Cellular Function ». Genes 10, no 11 (6 novembre 2019) : 897. http://dx.doi.org/10.3390/genes10110897.
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The conserved eukaryotic DNA repair enzyme Tyrosyl-DNA phosphodiesterase I (Tdp1) removes a diverse array of adducts from the end of DNA strand breaks. Tdp1 specifically catalyzes the hydrolysis of phosphodiester linked DNA-adducts. These DNA lesions range from damaged nucleotides to peptide-DNA adducts to protein-DNA covalent complexes and are products of endogenously or exogenously induced insults or simply failed reaction products. These adducts include DNA inserted ribonucleotides and non-conventional nucleotides, as well as covalent reaction intermediates of DNA topoisomerases with DNA and a Tdp1-DNA adduct in trans. This implies that Tdp1 plays a role in maintaining genome stability and cellular homeostasis. Dysregulation of Tdp1 protein levels or catalysis shifts the equilibrium to genome instability and is associated with driving human pathologies such as cancer and neurodegeneration. In this review, we highlight the function of the N-terminal domain of Tdp1. This domain is understudied, structurally unresolved, and the least conserved in amino acid sequence and length compared to the rest of the enzyme. However, over time it emerged that the N-terminal domain was post-translationally modified by, among others, phosphorylation, SUMOylation, and Ubiquitinoylation, which regulate Tdp1 protein interactions with other DNA repair associated proteins, cellular localization, and Tdp1 protein stability.
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Paskevicius, Tautvydas, Rabih Abou Farraj, Marek Michalak et Luis B. Agellon. « Calnexin, More than Just a Molecular Chaperone ». Cells 12, no 3 (24 janvier 2023) : 403. http://dx.doi.org/10.3390/cells12030403.
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Calnexin is a type I integral endoplasmic reticulum (ER) membrane protein with an N-terminal domain that resides in the lumen of the ER and a C-terminal domain that extends into the cytosol. Calnexin is commonly referred to as a molecular chaperone involved in the folding and quality control of membrane-associated and secreted proteins, a function that is attributed to its ER- localized domain with a structure that bears a strong resemblance to another luminal ER chaperone and Ca2+-binding protein known as calreticulin. Studies have discovered that the cytosolic C-terminal domain of calnexin undergoes distinct post-translational modifications and interacts with a variety of proteins. Here, we discuss recent findings and hypothesize that the post-translational modifications of the calnexin C-terminal domain and its interaction with specific cytosolic proteins play a role in coordinating ER functions with events taking place in the cytosol and other cellular compartments.
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Engle, Sarah M., Justin J. Crowder, Sheldon G. Watts, Christopher J. Indovina, Samuel Z. Coffey et Eric M. Rubenstein. « Acetylation of N-terminus and two internal amino acids is dispensable for degradation of a protein that aberrantly engages the endoplasmic reticulum translocon ». PeerJ 5 (22 août 2017) : e3728. http://dx.doi.org/10.7717/peerj.3728.
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Conserved homologues of the Hrd1 ubiquitin ligase target for degradation proteins that persistently or aberrantly engage the endoplasmic reticulum translocon, including mammalian apolipoprotein B (apoB; the major protein component of low-density lipoproteins) and the artificial yeast protein Deg1-Sec62. A complete understanding of the molecular mechanism by which translocon-associated proteins are recognized and degraded may inform the development of therapeutic strategies for cholesterol-related pathologies. Both apoB and Deg1-Sec62 are extensively post-translationally modified. Mass spectrometry of a variant of Deg1-Sec62 revealed that the protein is acetylated at the N-terminal methionine and two internal lysine residues. N-terminal and internal acetylation regulates the degradation of a variety of unstable proteins. However, preventing N-terminal and internal acetylation had no detectable consequence for Hrd1-mediated proteolysis of Deg1-Sec62. Our data highlight the importance of empirically validating the role of post-translational modifications and sequence motifs on protein degradation, even when such elements have previously been demonstrated sufficient to destine other proteins for destruction.
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Yao, Shixiang, et Chibuike C. Udenigwe. « Peptidomics of potato protein hydrolysates : implications of post-translational modifications in food peptide structure and behaviour ». Royal Society Open Science 5, no 7 (juillet 2018) : 172425. http://dx.doi.org/10.1098/rsos.172425.
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Post-translational modifications (PTMs) often occur in proteins and play a regulatory role in protein function. There is an increasing interest in the bioactivity of food protein-derived peptides, but the occurrence of PTMs and their influence on food peptide structure and behaviour remain largely unknown. In this study, the shotgun-based peptidomics strategy was used to identify the occurrence of PTMs in peptides generated from potato protein hydrolysis using digestive proteases. Diverse PTMs were found in the potato peptides, including acetylation of lysine, N-terminal of proteins and peptides, C-terminal amidation, de-amidation of asparagine/glutamine, methylation and trimethylation, methionine oxidation and N-terminal pyro-glutamyl residue formation. The modifications may have been formed naturally or as a result of chemical reactions during isolation and enzymatic processing of the potato proteins. Most of the PTMs were calculated to decrease the isoelectric point and increase molecular hydrophobicity of the peptides, which will influence their bioactivity while also potentially altering their solubility in an aqueous environment. This is the first study to unravel that food-derived peptides can be widely modified by PTMs associated with notable changes in peptide chemical properties. The findings have broader implications on the bioavailability, biomolecular interactions and biological activities of food peptides.
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Umelo-Njaka, Elizabeth, Wade H. Bingle, Faten Borchani, Khai D. Le, Peter Awram, Theo Blake, John F. Nomellini et John Smit. « Caulobacter crescentus Synthesizes an S-Layer-Editing Metalloprotease Possessing a Domain Sharing Sequence Similarity with Its Paracrystalline S-Layer Protein ». Journal of Bacteriology 184, no 10 (15 mai 2002) : 2709–18. http://dx.doi.org/10.1128/jb.184.10.2709-2718.2002.
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ABSTRACT Strains of Caulobacter crescentus elaborate an S-layer, a two-dimensional protein latticework which covers the cell surface. The S-layer protein (RsaA) is secreted by a type I mechanism (relying on a C-terminal signal) and is unusual among type I secreted proteins because high levels of protein are produced continuously. In efforts to adapt the S-layer for display of foreign peptides and proteins, we noted a proteolytic activity that affected S-layer monomers with foreign inserts. The cleavage was precise, resulting in fragments with an unambiguous N-terminal sequence. We developed an assay to screen for loss of this activity (i.e., presentation of foreign peptides without degradation), using transposon and traditional mutagenesis. A metalloprotease gene designated sap (S-layer-associated protease) was identified which could complement the protease-negative mutants. The N-terminal half of Sap possessed significant similarity to other type I secreted proteases (e.g., alkaline protease of Pseudomonas aeruginosa), including the characteristic RTX repeat sequences, but the C-terminal half which normally includes the type I secretion signal exhibited no such similarity. Instead, there was a region of significant similarity to the N-terminal region of RsaA. We hypothesize that Sap evolved by combining the catalytic portion of a type I secreted protease with an S-layer-like protein, perhaps to associate with nascent S-layer monomers to “scan” for modifications.
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Schwarz-Ben Meir, N., T. Glaser et N. S. Kosower. « Band 3 protein degradation by calpain is enhanced in erythrocytes of old people ». Biochemical Journal 275, no 1 (1 avril 1991) : 47–52. http://dx.doi.org/10.1042/bj2750047.
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Band 3 protein is a major erythrocyte transmembrane glycoprotein. We compared the degradation of band 3 protein by calpain I (a cytoplasmic, micromolar-Ca2(+)-requiring thiol proteinase) in the cells from old individuals (greater than 70 years old) to that in the cells from young ones (20-30 years old). In the young, little degradation of band 3 protein occurred in calpain-treated erythrocyte ghosts. In the old, significant band 3 protein degradation was found in erythrocyte ghosts treated similarly. The difference between young and old in the susceptibility of band 3 protein to calpain was retained in membrane vesicles (membranes stripped of peripheral proteins by NaOH) and in chymotrypsin-generated 60 kDa fragment (CH-60). The isolated N-terminal cytoplasmic 43 kDa fragment was degraded by calpain to a similar extent in old and in young. The separated 17 kDa membrane domain of the CH-60 and the trypsin-generated C-terminal 55 kDa membrane-spanning fragment were not degraded by calpain I in the young, nor in the old. Thus the N-terminal cytoplasmic domain is the domain degraded by calpain I. Enhanced sensitivity in the old is observed in intact band 3 protein and in CH-60, the isolated cytoplasmic domain being equally susceptible in young and old. The observed age-related enhanced sensitivity to calpain is consistent with the presence of modifications in band 3 protein and alterations in the association with the calpain-calpastatin system. Band 3 protein has several important functions, with modifications in the protein having implications for altered cell behaviour in the old individual.
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Wieczorek, Andrew, Clara K. Chan, Suzana Kovacic, Cindy Li, Thomas Dierks et Nancy R. Forde. « Genetically modified human type II collagen for N- and C-terminal covalent tagging ». Canadian Journal of Chemistry 96, no 2 (février 2018) : 204–11. http://dx.doi.org/10.1139/cjc-2017-0335.
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Collagen is the predominant structural protein in vertebrates, where it contributes to connective tissues and the ECM; it is also widely used in biomaterials and tissue engineering. Dysfunction of this protein and its processing can lead to a wide variety of developmental disorders and connective tissue diseases. Recombinantly engineering the protein is challenging due to post-translational modifications generally required for its stability and secretion from cells. Introducing end labels into the protein is problematic, because the N- and C-termini of the physiologically relevant tropocollagen lie internal to the initially flanking N- and C-propeptide sequences. Here, we introduce mutations into human type II procollagen in a manner that addresses these concerns and purify the recombinant protein from a stably transfected HT1080 human fibrosarcoma cell line. Our approach introduces chemically addressable groups into the N- and C-telopeptide termini of tropocollagen. Simultaneous overexpression of formylglycine generating enzyme (FGE) allows the endogenous production of an aldehyde tag in a defined, substituted sequence in the N terminus of the mutated collagen, whereas the C-terminus of each chain presents a sulfhydryl group from an introduced cysteine. These modifications are designed to enable specific covalent end-labelling of collagen. We find that the doubly mutated protein folds and is secreted from cells. Higher order assembly into well-ordered collagen fibrils is demonstrated through transmission electron microscopy. Chemical tagging of thiols is successful; however, background from endogenous aldehydes present in wild-type collagen has thus far obscured the desired specific N-terminal labelling. Strategies to overcome this challenge are proposed.
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Starheim, Kristian K., Darina Gromyko, Rune Evjenth, Anita Ryningen, Jan Erik Varhaug, Johan R. Lillehaug et Thomas Arnesen. « Knockdown of Human Nα-Terminal Acetyltransferase Complex C Leads to p53-Dependent Apoptosis and Aberrant Human Arl8b Localization ». Molecular and Cellular Biology 29, no 13 (27 avril 2009) : 3569–81. http://dx.doi.org/10.1128/mcb.01909-08.
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ABSTRACT Protein Nα-terminal acetylation is one of the most common protein modifications in eukaryotic cells. In yeast, three major complexes, NatA, NatB, and NatC, catalyze nearly all N-terminal acetylation, acetylating specific subsets of protein N termini. In human cells, only the NatA and NatB complexes have been described. We here identify and characterize the human NatC (hNatC) complex, containing the catalytic subunit hMak3 and the auxiliary subunits hMak10 and hMak31. This complex associates with ribosomes, and hMak3 acetylates Met-Leu protein N termini in vitro, suggesting a model in which the human NatC complex functions in cotranslational N-terminal acetylation. Small interfering RNA-mediated knockdown of NatC subunits results in p53-dependent cell death and reduced growth of human cell lines. As a consequence of hMAK3 knockdown, p53 is stabilized and phosphorylated and there is a significant transcriptional activation of proapoptotic genes downstream of p53. Knockdown of hMAK3 alters the subcellular localization of the Arf-like GTPase hArl8b, supporting that hArl8b is a hMak3 substrate in vivo. Taken together, hNatC-mediated N-terminal acetylation is important for maintenance of protein function and cell viability in human cells.
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Cornish, Jasmine, Darerca Owen et Helen R. Mott. « RLIP76 : A Structural and Functional Triumvirate ». Cancers 13, no 9 (4 mai 2021) : 2206. http://dx.doi.org/10.3390/cancers13092206.
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RLIP76/RalBP1 is an ATP-dependent transporter of glutathione conjugates, which is overexpressed in various human cancers, but its diverse functions in normal cells, which include endocytosis, stress response and mitochondrial dynamics, are still not fully understood. The protein can be divided into three distinct regions, each with its own structural properties. At the centre of the protein are two well-defined domains, a GTPase activating protein domain targeting Rho family small G proteins and a small coiled-coil that binds to the Ras family small GTPases RalA and RalB. In engaging with Rho and Ral proteins, RLIP76 bridges these two distinct G protein families. The N-terminal region is predicted to be disordered and is rich in basic amino acids, which may mediate membrane association, consistent with its role in transport. RLIP76 is an ATP-dependent transporter with ATP-binding sites within the N-terminus and the Ral binding domain. Furthermore, RLIP76 is subject to extensive phosphorylation, particularly in the N-terminal region. In contrast, the C-terminal region is thought to form an extensive coiled-coil that could mediate dimerization. Here, we review the structural features of RLIP76, including experimental data and computational predictions, and discuss the implications of its various post-translational modifications.
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Ogino, Tomoaki, Hiroyuki Fukuda, Shinobu Imajoh-Ohmi, Michinori Kohara et Akio Nomoto. « Membrane Binding Properties and Terminal Residues of the Mature Hepatitis C Virus Capsid Protein in Insect Cells ». Journal of Virology 78, no 21 (1 novembre 2004) : 11766–77. http://dx.doi.org/10.1128/jvi.78.21.11766-11777.2004.
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ABSTRACT The immature core protein (p23, residues 1 to 191) of hepatitis C virus undergoes posttranslational modifications including intramembranous proteolysis within its C-terminal signal sequence by signal peptide peptidase to generate the mature form (p21). In this study, we analyzed the cleavage site and other amino acid modifications that occur on the core protein. To produce the posttranslationally modified core protein, we used a baculovirus-insect cell expression model system. As previously reported, p23 is processed to form p21 in insect as well as in mammalian cells. p21 was found to be associated with the cytoplasmic membrane, and its significant portion behaved as an integral membrane protein. The protein was purified from the membrane by a simple and unique procedure on the basis of its membrane-binding properties and solubility in detergents. Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) analysis of purified p21 showed that the average molecular mass (m/z 19,307) of its single-charged ion differs by m/z 1,457 from that calculated for p23. To determine the posttranslational modifications, tryptic p21 peptides were analyzed by MALDI-TOF MS. We found three peptides that did not match the theoretically derived peptides of p23. Analysis of these peptides by MALDI-TOF tandem MS revealed that they correspond to N-terminal peptides (residues 2 to 9 and 2 to 10) starting with α-N-acetylserine and C-terminal peptide (residues 150 to 177) ending with phenylalanine. These results suggest that the mature core protein (molecular mass of 19,306 Da) includes residues 2 to 177 and that its N terminus is blocked with an acetyl group.
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Webber, Matthew J., Eric A. Appel, Brittany Vinciguerra, Abel B. Cortinas, Lavanya S. Thapa, Siddharth Jhunjhunwala, Lyle Isaacs, Robert Langer et Daniel G. Anderson. « Supramolecular PEGylation of biopharmaceuticals ». Proceedings of the National Academy of Sciences 113, no 50 (28 novembre 2016) : 14189–94. http://dx.doi.org/10.1073/pnas.1616639113.
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The covalent modification of therapeutic biomolecules has been broadly explored, leading to a number of clinically approved modified protein drugs. These modifications are typically intended to address challenges arising in biopharmaceutical practice by promoting improved stability and shelf life of therapeutic proteins in formulation, or modifying pharmacokinetics in the body. Toward these objectives, covalent modification with poly(ethylene glycol) (PEG) has been a common direction. Here, a platform approach to biopharmaceutical modification is described that relies on noncovalent, supramolecular host–guest interactions to endow proteins with prosthetic functionality. Specifically, a series of cucurbit[7]uril (CB[7])–PEG conjugates are shown to substantially increase the stability of three distinct protein drugs in formulation. Leveraging the known and high-affinity interaction between CB[7] and an N-terminal aromatic residue on one specific protein drug, insulin, further results in altering of its pharmacological properties in vivo by extending activity in a manner dependent on molecular weight of the attached PEG chain. Supramolecular modification of therapeutic proteins affords a noncovalent route to modify its properties, improving protein stability and activity as a formulation excipient. Furthermore, this offers a modular approach to append functionality to biopharmaceuticals by noncovalent modification with other molecules or polymers, for applications in formulation or therapy.
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Bennick, A. « Structural and Genetic Aspects of Proline-rich Proteins ». Journal of Dental Research 66, no 2 (février 1987) : 457–61. http://dx.doi.org/10.1177/00220345870660021201.
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Considerable advances have been made in the genetics of salivary proline-rich proteins (PRP). The genes for acidic, basic, and glycosylated PRP have been cloned. They code for precursor proteins that all have an acidic N-terminal followed by proline-rich repeat sequences. Structural studies on secreted proteins have demonstrated that not only acidic but also some basic PRPs have this general structure. It is possible that mRNA for different PRP may have originated from a single gene by differential mRNA splicing, but post-translational cleavages of the primary translation product apparently also occur. In vitro translation of salivary gland mRNA results in a single precursor protein for acidic PRP. Such in vitro translated protein can be cleaved by salivary kallikrein, giving rise to two commonly secreted acidic PRPs, and kallikrein or kallikrein-like enzymes may be responsible for other post-translational cleavages of PRPs. Acidic as well as some basic PRPs are phosphorylated. A protein kinase has been demonstrated in salivary glands which phosphorylates the PRPs and other secreted salivary proteins in a cAMP and Ca2+-calmodulinindependent manner. Knowledge of the conformation of PRPs is limited. There is no conclusive evidence of polyproline-like structure in the proline-rich part of PRPs. Ca2+ binding studies on acidic PRPs indicate that there is interaction between the Ca2+ binding N-terminal end and the proline-rich C-terminal part. This interaction is relieved by modification of arginine side-chains. 1H, 32P, and 43Ca NMR studies have further elucidated the conformation of acidic PRPs in solution. Present evidence shows that salivary PRPs constitute a unique superfamily of proteins which pose a number of interesting questions concerning gene structure, pre- and post-translational modifications, and protein conformation.
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Franco, Aitor, Jorge Cuéllar, José Ángel Fernández-Higuero, Igor de la Arada, Natalia Orozco, José M. Valpuesta, Adelina Prado et Arturo Muga. « Truncation-Driven Lateral Association of α-Synuclein Hinders Amyloid Clearance by the Hsp70-Based Disaggregase ». International Journal of Molecular Sciences 22, no 23 (30 novembre 2021) : 12983. http://dx.doi.org/10.3390/ijms222312983.
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The aggregation of α-synuclein is the hallmark of a collective of neurodegenerative disorders known as synucleinopathies. The tendency to aggregate of this protein, the toxicity of its aggregation intermediates and the ability of the cellular protein quality control system to clear these intermediates seems to be regulated, among other factors, by post-translational modifications (PTMs). Among these modifications, we consider herein proteolysis at both the N- and C-terminal regions of α-synuclein as a factor that could modulate disassembly of toxic amyloids by the human disaggregase, a combination of the chaperones Hsc70, DnaJB1 and Apg2. We find that, in contrast to aggregates of the protein lacking the N-terminus, which can be solubilized as efficiently as those of the WT protein, the deletion of the C-terminal domain, either in a recombinant context or as a consequence of calpain treatment, impaired Hsc70-mediated amyloid disassembly. Progressive removal of the negative charges at the C-terminal region induces lateral association of fibrils and type B* oligomers, precluding chaperone action. We propose that truncation-driven aggregate clumping impairs the mechanical action of chaperones, which includes fast protofilament unzipping coupled to depolymerization. Inhibition of the chaperone-mediated clearance of C-truncated species could explain their exacerbated toxicity and higher propensity to deposit found in vivo.
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Abdul, Shiraazkhan, Frank W. G. Leebeek, Dingeman C. Rijken et Shirley Uitte de Willige. « Natural heterogeneity of α2-antiplasmin : functional and clinical consequences ». Blood 127, no 5 (4 février 2016) : 538–45. http://dx.doi.org/10.1182/blood-2015-09-670117.
Texte intégralRésumé :
AbstractHuman α2-antiplasmin (α2AP, also called α2-plasmin inhibitor) is the main physiological inhibitor of the fibrinolytic enzyme plasmin. α2AP inhibits plasmin on the fibrin clot or in the circulation by forming plasmin-antiplasmin complexes. Severely reduced α2AP levels in hereditary α2AP deficiency may lead to bleeding symptoms, whereas increased α2AP levels have been associated with increased thrombotic risk. α2AP is a very heterogeneous protein. In the circulation, α2AP undergoes both amino terminal (N-terminal) and carboxyl terminal (C-terminal) proteolytic modifications that significantly modify its activities. About 70% of α2AP is cleaved at the N terminus by antiplasmin-cleaving enzyme (or soluble fibroblast activation protein), resulting in a 12-amino-acid residue shorter form. The glutamine residue that serves as a substrate for activated factor XIII becomes more efficient after removal of the N terminus, leading to faster crosslinking of α2AP to fibrin and consequently prolonged clot lysis. In approximately 35% of circulating α2AP, the C terminus is absent. This C terminus contains the binding site for plasmin(ogen), the key component necessary for the rapid and efficient inhibitory mechanism of α2AP. Without its C terminus, α2AP can no longer bind to the lysine binding sites of plasmin(ogen) and is only a kinetically slow plasmin inhibitor. Thus, proteolytic modifications of the N and C termini of α2AP constitute major regulatory mechanisms for the inhibitory function of the protein and may therefore have clinical consequences. This review presents recent findings regarding the main aspects of the natural heterogeneity of α2AP with particular focus on the functional and possible clinical implications.
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Ji, Chengjie, Zhengping Wang et Liang Li. « Protein mass measurement combined with mass spectrometric sequencing of protein digests for detection and characterization of protein modifications1 ». Canadian Journal of Chemistry 84, no 7 (1 juillet 2006) : 986–97. http://dx.doi.org/10.1139/v06-114.
Texte intégralRésumé :
A method for the characterization of modifications of low molecular weight proteins (<20 kDa) extracted from a microorganism based on the use of multiple separation tools and mass spectrometric techniques is described. In this method, intact proteins from cell extracts are first separated and fractionated by liquid chromatography (LC). Individual fractions are then analyzed by matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS) to provide intact protein mass information. The fractions are further characterized by using trypsin digestion and LC electrospray ionization (ESI) MS/MS analysis of the resultant peptides to identify the proteins. Gel electrophoresis of a fraction is also carried out to estimate the molecular masses of the proteins. The gel bands are identified by in-gel digestion and peptide mass mapping and sequencing using MALDI-MS and MALDI-MS/MS. The combined information generated from these experiments is interpreted for detecting and characterizing modified proteins. This method has been developed and applied to the analysis of posttranslational modifications (PTMs) of low-mass proteins (5–20 kDa) extracted from a relatively well-characterized microorganism, Escherichia coli. Using this method, not only previously reported PTMs involving acetylation, methylation, oxidation, and the removal of signal peptides, but also two novel PTMs, namely loss of N-terminal Met-Thr-Met (MTM) and hydroxylation of arginine, were identified. It is envisaged that this method should be applicable to other relatively simple microorganisms for the discovery of new PTMs.Key words: top-down proteomics, protein modification, HPLC, gel electrophoresis, tandem mass spectrometry.
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Sharma, Ajit K., Abhilasha Mansukh, Ashok Varma, Nikhil Gadewal et Sanjay Gupta. « Molecular Modeling of Differentially Phosphorylated Serine 10 and Acetylated lysine 9/14 of Histone H3 Regulates their Interactions with 14-3-3ζ, MSK1, and MKP1 ». Bioinformatics and Biology Insights 7 (janvier 2013) : BBI.S12449. http://dx.doi.org/10.4137/bbi.s12449.
Texte intégralRésumé :
Histone modifications occur in precise patterns, with several modifications known to affect the binding of proteins. These interactions affect the chromatin structure, gene regulation, and cell cycle events. The dual modifications on the H3 tail, serine10 phosphorylation, and lysine14 acetylation (H3Ser10PLys14Ac) are reported to be crucial for interaction with 14-3-3ζ. However, the mechanism by which H3Ser10P along with neighboring site-specific acetylation(s) is targeted by its regulatory proteins, including kinase and phosphatase, is not fully understood. We carried out molecular modeling studies to understand the interaction of 14-3-3ζ, and its regulatory proteins, mitogen-activated protein kinase phosphatase-1 (MKP1), and mitogen- and stress-activated protein kinase-1 (MSK1) with phosphorylated H3Ser10 alone or in combination with acetylated H3Lys9 and Lys14. In silico molecular association studies suggested that acetylated Lys14 and phosphorylated Ser10 of H3 shows the highest binding affinity towards 14-3-3ζ. In addition, acetylation of H3Lys9 along with Ser10PLys14Ac favors the interaction of the phosphatase, MKP1, for dephosphorylation of H3Ser10P. Further, MAP kinase, MSK1 phosphorylates the unmodified H3Ser10 containing N-terminal tail with maximum affinity compared to the N-terminal tail with H3Lys9AcLys14Ac. The data clearly suggest that opposing enzymatic activity of MSK1 and MKP1 corroborates with non-acetylated and acetylated, H3Lys9Lys14, respectively. Our in silico data highlights that site-specific phosphorylation (H3Ser10P) and acetylation (H3Lys9 and H3Lys14) of H3 are essential for the interaction with their regulatory proteins (MKP1, MSK1, and 14-3-3ζ) and plays a major role in the regulation of chromatin structure.
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Zlatkine, P., B. Mehul et A. I. Magee. « Retargeting of cytosolic proteins to the plasma membrane by the Lck protein tyrosine kinase dual acylation motif ». Journal of Cell Science 110, no 5 (1 mars 1997) : 673–79. http://dx.doi.org/10.1242/jcs.110.5.673.
Texte intégralRésumé :
Several members of the Src family of protein tyrosine kinases have a N-terminal dual acylation motif which specifies their myristoylation and S-acylation. These lipid modifications are necessary for correct intracellular localisation to the plasma membrane and to detergent-resistant glycolipid-enriched membrane domains (GEMs). Using chimaeras of the Lck dual acylation motif with two normally cytosolic proteins (chloramphenicol acetyl transferase and galectin-3), we show here that this motif is sufficient to encode correct lipid modification and to target these chimaeras to the plasma membrane, as demonstrated by subcellular fractionation and confocal immunofluorescence microscopy of transiently transfected COS cells. In addition, the chimaeras are resistant to extraction with cold non-ionic detergent, indicating targeting to GEM subdomains in the plasma membrane. The dual acylation motif has potential for targeting proteins to specific plasma membrane subdomains involved in signalling.
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Azevedo, Cristina, et Adolfo Saiardi. « The new world of inorganic polyphosphates ». Biochemical Society Transactions 44, no 1 (9 février 2016) : 13–17. http://dx.doi.org/10.1042/bst20150210.
Texte intégralRésumé :
Post-translational modifications (PTMs) add regulatory features to proteins that help establish the complex functional networks that make up higher organisms. Advances in analytical detection methods have led to the identification of more than 200 types of PTMs. However, some modifications are unstable under the present detection methods, anticipating the existence of further modifications and a much more complex map of PTMs. An example is the recently discovered protein modification polyphosphorylation. Polyphosphorylation is mediated by inorganic polyphosphate (polyP) and represents the covalent attachment of this linear polymer of orthophosphate to lysine residues in target proteins. This modification has eluded MS analysis as both polyP itself and the phosphoramidate bonds created upon its reaction with lysine residues are highly unstable in acidic conditions. Polyphosphorylation detection was only possible through extensive biochemical characterization. Two targets have been identified: nuclear signal recognition 1 (Nsr1) and its interacting partner, topoisomerase 1 (Top1). Polyphosphorylation occurs within a conserved N-terminal polyacidic serine (S) and lysine (K) rich (PASK) cluster. It negatively regulates Nsr1–Top1 interaction and impairs Top1 enzymatic activity, namely relaxing supercoiled DNA. Modulation of cellular levels of polyP regulates Top1 activity by modifying its polyphosphorylation status. Here we discuss the significance of the recently identified new role of inorganic polyP.
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Shuvo, Sabbir R., Uliana Kovaltchouk, Abdullah Zubaer, Ayush Kumar, William A. T. Summers, Lynda J. Donald, Georg Hausner et Deborah A. Court. « Functional characterization of an N-terminally-truncated mitochondrial porin expressed in Neurospora crassa ». Canadian Journal of Microbiology 63, no 8 (août 2017) : 730–38. http://dx.doi.org/10.1139/cjm-2016-0764.
Texte intégralRésumé :
Mitochondrial porin, which forms voltage-dependent anion-selective channels (VDAC) in the outer membrane, can be folded into a 19-β-stranded barrel. The N terminus of the protein is external to the barrel and contains α-helical structure. Targeted modifications of the N-terminal region have been assessed in artificial membranes, leading to different models for gating in vitro. However, the in vivo requirements for gating and the N-terminal segment of porin are less well-understood. Using Neurospora crassa porin as a model, the effects of a partial deletion of the N-terminal segment were investigated. The protein, ΔN2-12porin, is assembled into the outer membrane, albeit at lower levels than the wild-type protein. The resulting strain displays electron transport chain deficiencies, concomitant expression of alternative oxidase, and decreased growth rates. Nonetheless, its mitochondrial genome does not contain any significant mutations. Most of the genes that are expressed in high levels in porin-less N. crassa are expressed at levels similar to that of wild type or are slightly increased in ΔN2-12porin strains. Thus, although the N-terminal segment of VDAC is required for complete function in vivo, low levels of a protein lacking part of the N terminus are able to rescue some of the defects associated with the absence of porin.
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Nevitt, Chris, John G. Tooley et Christine E. Schaner Tooley. « N-terminal acetylation and methylation differentially affect the function of MYL9 ». Biochemical Journal 475, no 20 (23 octobre 2018) : 3201–19. http://dx.doi.org/10.1042/bcj20180638.
Texte intégralRésumé :
Deciphering the histone code has illustrated that acetylation or methylation on the same residue can have analogous or opposing roles. However, little is known about the interplay between these post-translational modifications (PTMs) on the same nonhistone residues. We have recently discovered that N-terminal acetyltransferases (NATs) and N-terminal methyltransferases (NRMTs) can have overlapping substrates and identified myosin regulatory light chain 9 (MYL9) as the first confirmed protein to occur in either α-amino-methylated (Nα-methyl) or α-amino-acetylated (Nα-acetyl) states in vivo. Here we aim to determine if these PTMs function similarly or create different MYL9 proteoforms with distinct roles. We use enzymatic assays to directly verify MYL9 is a substrate of both NRMT1 and NatA and generate mutants of MYL9 that are exclusive for Nα-acetylation or Nα-methylation. We then employ eukaryotic cell models to probe the regulatory functions of these Nα-PTMs on MYL9. Our results show that, contrary to prevailing dogma, neither of these modifications regulate the stability of MYL9. Rather, exclusive Nα-acetylation promotes cytoplasmic roles of MYL9, while exclusive Nα-methylation promotes the nuclear role of MYL9 as a transcription factor. The increased cytoplasmic activity of Nα-acetylated MYL9 corresponds with increased phosphorylation at serine 19, a key MYL9 activating PTM. Increased nuclear activity of Nα-methylated MYL9 corresponds with increased DNA binding. Nα-methylation also results in a decrease of interactions between the N-terminus of MYL9 and a host of cytoskeletal proteins. These results confirm that Nα-acetylation and Nα-methylation differentially affect MYL9 function by creating distinct proteoforms with different internal PTM patterns and binding properties.
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Crandall, I., et I. W. Sherman. « Plasmodium falciparum (human malaria)-induced modifications in human erythrocyte band 3 protein ». Parasitology 102, no 3 (juin 1991) : 335–40. http://dx.doi.org/10.1017/s0031182000064271.
Texte intégralRésumé :
A monoclonal antibody, 1C4, was produced which recognizes a 65 kDa protein that is localized to the plasma membrane of human erythrocytes infected with Plasmodium falciparum. By immunofluorescence the antigen was visualized as dots on the surface of the infected cell. The 65 kDa protein was present in 4 strains of diverse geographical origin, and in erythrocytes infected with a knobless strain. The 65 kDa protein was insoluble in non-ionic detergents, but was partly soluble in SDS and some high (1 M) śalt solutions. The 65 kDa protein is recognized by antibodies specific for the cytoplasmic domain and the N-terminal side of the membrane-spanning region of human band 3, but was not recognized by an antibody specific to the C-terminal side of the membrane-spanning region. The results of treatment of the 65 kDa protein with trypsin and chymotrypsin are consistent with the 65 kDa protein being a truncated and covalently modified band 3 molecule which consists of the first 540 amino acids of human band 3.
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Feng, Jinlin, Jianxin Hu, Yan Li, Ruiqi Li, Hao Yu et Ligeng Ma. « The N-Terminal Acetyltransferase Naa50 Regulates Arabidopsis Growth and Osmotic Stress Response ». Plant and Cell Physiology 61, no 9 (16 juin 2020) : 1565–75. http://dx.doi.org/10.1093/pcp/pcaa081.
Texte intégralRésumé :
Abstract N-terminal acetylation (Nt-acetylation) is one of the most common protein modifications in eukaryotes. The function of Naa50, the catalytic subunit of the evolutionarily conserved N-terminal acetyltransferase (Nat) E complex, has not been reported in Arabidopsis. In this study, we found that a loss of Naa50 resulted in a pleiotropic phenotype that included dwarfism and sterility, premature leaf senescence and a shortened primary root. Further analysis revealed that root cell patterning and various root cell properties were severely impaired in naa50 mutant plants. Moreover, defects in auxin distribution were observed due to the mislocalization of PIN auxin transporters. In contrast to its homologs in yeast and animals, Naa50 showed no co-immunoprecipitation with any subunit of the Nat A complex. Moreover, plants lacking Naa50 displayed hypersensitivity to abscisic acid and osmotic stress. Therefore, our results suggest that protein N-terminal acetylation catalyzed by Naa50 plays an essential role in Arabidopsis growth and osmotic stress responses.
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Beranger, F., H. Paterson, S. Powers, J. de Gunzburg et J. F. Hancock. « The effector domain of Rab6, plus a highly hydrophobic C terminus, is required for Golgi apparatus localization ». Molecular and Cellular Biology 14, no 1 (janvier 1994) : 744–58. http://dx.doi.org/10.1128/mcb.14.1.744-758.1994.
Texte intégralRésumé :
C-terminal lipid modifications are essential for the interaction of Ras-related proteins with membranes. While all Ras proteins are farnesylated and some palmitoylated, the majority of other Ras-related proteins are geranylgeranylated. One such protein, Rab6, is associated with the Golgi apparatus and has a C-terminal CXC motif that is geranylgeranylated on both cysteines. We show here that farnesylation alone cannot substitute for geranylgeranylation in targeting Rab6 to the Golgi apparatus and that whereas Ras proteins that are farnesylated and palmitoylated are targeted to the plasma membrane, mutant Rab proteins that are both farnesylated and palmitoylated associate with the Golgi apparatus. Using chimeric Ras-Rab proteins, we find that there are sequences in the N-terminal 71 amino acids of Rab6 which are required for Golgi complex localization and show that these sequences comprise or include the effector domain. The C-terminal hypervariable domain is not essential for the Golgi complex targeting of Rab6 but is required to prevent prenylated and palmitoylated Rab6 from localizing to the plasma membrane. Functional analysis of these mutant Rab6 proteins in Saccharomyces cerevisiae shows that wild-type Rab6 and C-terminal mutant Rab6 proteins which localize to the Golgi apparatus in mammalian cells can complement the temperature-sensitive phenotype of ypt6 null mutants. Interestingly, therefore, the C-terminal hypervariable domain of Rab6 is not required for this protein to function in S. cerevisiae.
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Beranger, F., H. Paterson, S. Powers, J. de Gunzburg et J. F. Hancock. « The effector domain of Rab6, plus a highly hydrophobic C terminus, is required for Golgi apparatus localization. » Molecular and Cellular Biology 14, no 1 (janvier 1994) : 744–58. http://dx.doi.org/10.1128/mcb.14.1.744.
Texte intégralRésumé :
C-terminal lipid modifications are essential for the interaction of Ras-related proteins with membranes. While all Ras proteins are farnesylated and some palmitoylated, the majority of other Ras-related proteins are geranylgeranylated. One such protein, Rab6, is associated with the Golgi apparatus and has a C-terminal CXC motif that is geranylgeranylated on both cysteines. We show here that farnesylation alone cannot substitute for geranylgeranylation in targeting Rab6 to the Golgi apparatus and that whereas Ras proteins that are farnesylated and palmitoylated are targeted to the plasma membrane, mutant Rab proteins that are both farnesylated and palmitoylated associate with the Golgi apparatus. Using chimeric Ras-Rab proteins, we find that there are sequences in the N-terminal 71 amino acids of Rab6 which are required for Golgi complex localization and show that these sequences comprise or include the effector domain. The C-terminal hypervariable domain is not essential for the Golgi complex targeting of Rab6 but is required to prevent prenylated and palmitoylated Rab6 from localizing to the plasma membrane. Functional analysis of these mutant Rab6 proteins in Saccharomyces cerevisiae shows that wild-type Rab6 and C-terminal mutant Rab6 proteins which localize to the Golgi apparatus in mammalian cells can complement the temperature-sensitive phenotype of ypt6 null mutants. Interestingly, therefore, the C-terminal hypervariable domain of Rab6 is not required for this protein to function in S. cerevisiae.
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Suzuki, Takashi, Masaaki Ito, Toru Ezure, Masamitsu Shikata, Eiji Ando, Toshihiko Utsumi, Susumu Tsunasawa et Osamu Nishimura. « N-Terminal protein modifications in an insect cell-free protein synthesis system and their identification by mass spectrometry ». PROTEOMICS 6, no 16 (août 2006) : 4486–95. http://dx.doi.org/10.1002/pmic.200600126.
Texte intégral
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Yao, Xuejing, Guiping Qi, Yaocheng Qu, Shasha Yun, Wenlong Sun, Chungang Liang, Mupeng Du et Zhuanglin Li. « Structural Characterization of RC28-E, a Recombinant Fusion Protein With Dual Targets on VEGF and FGF2 ». Natural Product Communications 17, no 3 (mars 2022) : 1934578X2210869. http://dx.doi.org/10.1177/1934578x221086989.
Texte intégralRésumé :
Vascular endothelial growth factor (VEGF) and fibroblast growthfactor (FGF) play important roles in angiogenesis-related diseases. RC28-E is a soluble fusion protein composed of the human VEGF receptor 1 (VEGFR1) extracellular domain 2 (ECD 2), VEGFR2 ECD 3, FGFR1 ECDs 2 and 3, and the Fc regions of human immunoglobulin G1. By targeting both VEGF and FGF2, RC28-E may represent a useful antiangiogenetic agent, but structural and functional characterizations of this fusion protein are needed. Liquid chromatography–tandem mass spectrometry, size exclusion high-performance liquid chromatography, capillary electrophoresis-sodium dodecyl sulfate, imaged capillary isoelectric focusing, and bio-layer interferometry were used to characterize the properties of RC28-E. The purity of RC28-E was confirmed to be 98% or greater. The glycosylation modification of RC28-E was found to be very complicated, with 11 potential N-linked glycosylation points and 23 types of N-glycans, causing high heterogeneity of the protein. The primary modifications of the amino acid sequence of RC28-E protein included C-terminal K truncation, N-deamidation, and M-oxidation modification. Notably, RC28-E demonstrated a higher affinity for both VEGF and FGF2 than VEGF trap or FGF trap for their respective targets.
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Soshnikova, N. V., A. A. Sheynov, Eu V. Tatarskiy et S. G. Georgieva. « The DPF Domain As a Unique Structural Unit Participating in Transcriptional Activation, Cell Differentiation, and Malignant Transformation ». Acta Naturae 12, no 4 (22 décembre 2020) : 57–65. http://dx.doi.org/10.32607/actanaturae.11092.
Texte intégralRésumé :
The DPF (double PHD finger) domain consists of two PHD fingers organized in tandem. The two PHD-finger domains within a DPF form a single structure that interacts with the modification of the N-terminal histone fragment in a way different from that for single PHD fingers. Several histone modifications interacting with the DPF domain have already been identified. They include acetylation of H3K14 and H3K9, as well as crotonylation of H3K14. These modifications are found predominantly in transcriptionally active chromatin. Proteins containing DPF belong to two classes of protein complexes, which are the transcriptional coactivators involved in the regulation of the chromatin structure. These are the histone acetyltransferase complex belonging to the MYST family and the SWI/SNF chromatin-remodeling complex. The DPF domain is responsible for the specificity of the interactions between these complexes and chromatin. Proteins containing DPF play a crucial role in the activation of the transcription of a number of genes expressed during the development of an organism. These genes are important in the differentiation and malignant transformation of mammalian cells.
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Heissenberger, Clemens, Lisa Liendl, Fabian Nagelreiter, Yulia Gonskikh, Guohuan Yang, Elena M. Stelzer, Teresa L. Krammer et al. « Loss of the ribosomal RNA methyltransferase NSUN5 impairs global protein synthesis and normal growth ». Nucleic Acids Research 47, no 22 (13 novembre 2019) : 11807–25. http://dx.doi.org/10.1093/nar/gkz1043.
Texte intégralRésumé :
Abstract Modifications of ribosomal RNA expand the nucleotide repertoire and thereby contribute to ribosome heterogeneity and translational regulation of gene expression. One particular m5C modification of 25S ribosomal RNA, which is introduced by Rcm1p, was previously shown to modulate stress responses and lifespan in yeast and other small organisms. Here, we report that NSUN5 is the functional orthologue of Rcm1p, introducing m5C3782 into human and m5C3438 into mouse 28S ribosomal RNA. Haploinsufficiency of the NSUN5 gene in fibroblasts from William Beuren syndrome patients causes partial loss of this modification. The N-terminal domain of NSUN5 is required for targeting to nucleoli, while two evolutionary highly conserved cysteines mediate catalysis. Phenotypic consequences of NSUN5 deficiency in mammalian cells include decreased proliferation and size, which can be attributed to a reduction in total protein synthesis by altered ribosomes. Strikingly, Nsun5 knockout in mice causes decreased body weight and lean mass without alterations in food intake, as well as a trend towards reduced protein synthesis in several tissues. Together, our findings emphasize the importance of single RNA modifications for ribosome function and normal cellular and organismal physiology.
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Bleve, Gianluca, Giuseppe Zacheo, Maria Stella Cappello, Franco Dellaglio et Francesco Grieco. « Subcellular localization and functional expression of the glycerol uptake protein 1 (GUP1) of Saccharomyces cerevisiae tagged with green fluorescent protein ». Biochemical Journal 390, no 1 (9 août 2005) : 145–55. http://dx.doi.org/10.1042/bj20042045.
Texte intégralRésumé :
GFP (green fluorescent protein) from Aequorea victoria was used as an in vivo reporter protein when fused to the N- and C-termini of the glycerol uptake protein 1 (Gup1p) of Saccharomyces cerevisiae. The subcellular localization and functional expression of biologically active Gup1–GFP chimaeras was monitored by confocal laser scanning and electron microscopy, thus supplying the first study of GUP1 dynamics in live yeast cells. The Gup1p tagged with GFP is a functional glycerol transporter localized at the plasma membrane and endoplasmic reticulum levels of induced cells. The factors involved in proper localization and turnover of Gup1p were revealed by expression of the Gup1p–GFP fusion protein in a set of strains bearing mutations in specific steps of the secretory and endocytic pathways. The chimaerical protein was targeted to the plasma membrane through a Sec6-dependent process; on treatment with glucose, it was endocytosed through END3 and targeted for degradation in the vacuole. Gup1p belongs to the list of yeast proteins rapidly down-regulated by changing the carbon source in the culture medium, in agreement with the concept that post-translational modifications triggered by glucose affect proteins of peripheral functions. The immunoelectron microscopy assays of cells expressing either Gup1–GFP or GFP–Gup1 fusions suggested the Gup1p membrane topology: the N-terminus lies in the periplasmic space, whereas its C-terminal tail has an intracellular location. An extra cytosolic location of the N-terminal tail is not generally predicted or determined in yeast membrane transporters.
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Pauly, P. C., et C. Klein. « Lack of glycosyl-phosphatidylinositol anchoring leads to precursor retention by a unique mechanism in Dictyostelium discoideum ». Biochemical Journal 306, no 3 (15 mars 1995) : 643–50. http://dx.doi.org/10.1042/bj3060643.
Texte intégralRésumé :
Gp80, a cell-adhesion molecule in Dictyostelium discoideum, is modified by N- and O-linked oligosaccharides, and a glycosylphosphatidylinositol (GPI) anchor. To identify sequences important for the addition of these modifications to gp80, we created a hybrid protein in which the C-terminal 136 amino acids of yeast invertase were replaced by the C-terminal 110 amino acids of gp80. When expressed in D. discoideum, this protein (Inv-gp80) was not GPI-anchored and was retained in a pre-Golgi compartment. Inv-gp80 did, however, display characteristics of a transmembrane protein, suggesting a novel mechanism for its retention. We also expressed a truncated version of the hybrid protein in which the C-terminal 22 amino acids of the Inv-gp80 were deleted. The truncated protein (Inv-gp80stop) was O-glycosylated and secreted. These observations indicate that the hybrid protein is not abnormally folded and demonstrate the importance of the C-terminal 22 amino acids in the retention of Inv-gp80. Together, the data suggest that oligomerization of the protein blocks its GPI anchoring.
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Shang, Tao, Chee Mun Fang, Chin Eng Ong et Yan Pan. « Heterologous Expression of Recombinant Human Cytochrome P450 (CYP) in Escherichia coli : N-Terminal Modification, Expression, Isolation, Purification, and Reconstitution ». BioTech 12, no 1 (7 février 2023) : 17. http://dx.doi.org/10.3390/biotech12010017.
Texte intégralRésumé :
Cytochrome P450 (CYP) enzymes play important roles in metabolising endogenous and xenobiotic substances. Characterisations of human CYP proteins have been advanced with the rapid development of molecular technology that allows heterologous expression of human CYPs. Among several hosts, bacteria systems such as Escherichia coli (E. coli) have been widely used thanks to their ease of use, high level of protein yields, and affordable maintenance costs. However, the levels of expression in E. coli reported in the literature sometimes differ significantly. This paper aims to review several contributing factors, including N-terminal modifications, co-expression with a chaperon, selections of vectors and E. coli strains, bacteria culture and protein expression conditions, bacteria membrane preparations, CYP protein solubilizations, CYP protein purifications, and reconstitution of CYP catalytic systems. The common factors that would most likely lead to high expression of CYPs were identified and summarised. Nevertheless, each factor may still require careful evaluation for individual CYP isoforms to achieve a maximal expression level and catalytic activity. Recombinant E. coli systems have been evidenced as a useful tool in obtaining the ideal level of human CYP proteins, which ultimately allows for subsequent characterisations of structures and functions.
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Kumar, Raj, et Iain J. McEwan. « Allosteric Modulators of Steroid Hormone Receptors : Structural Dynamics and Gene Regulation ». Endocrine Reviews 33, no 2 (20 mars 2012) : 271–99. http://dx.doi.org/10.1210/er.2011-1033.
Texte intégralRésumé :
Steroid hormones are synthesized from cholesterol primarily in the adrenal gland and the gonads and play vital roles in normal physiology, the control of development, differentiation, metabolic homeostasis, and reproduction. The actions of these small lipophilic molecules are mediated by intracellular receptor proteins. It is just over 25 yr since the first cDNA for steroid receptors were cloned, a development that led to the birth of a superfamily of ligand-activated transcription factors: the nuclear receptors. The receptor proteins share structurally and functionally related ligand binding and DNA-binding domains but possess distinct N-terminal domains and hinge regions that are intrinsically disordered. Since the original cloning experiments, considerable progress has been made in our understanding of the structure, mechanisms of action, and biology of this important class of ligand-activated transcription factors. In recent years, there has been interest in the structural plasticity and function of the N-terminal domain of steroid hormone receptors and in the allosteric regulation of protein folding and function in response to hormone, DNA response element architecture, and coregulatory protein binding partners. The N-terminal domain can exist as an ensemble of conformers, having more or less structure, which prime this region of the receptor to rapidly respond to changes in the intracellular environment through hormone binding and posttranslation modifications. In this review, we address the question of receptor structure and function dynamics with particular emphasis on the structurally flexible N-terminal domain, intra- and interdomain communications, and the allosteric regulation of receptor action.
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Reed, Brian D., Michael J. Meyer, Valentin Abramzon, Omer Ad, Omer Ad, Pat Adcock, Faisal R. Ahmad et al. « Real-time dynamic single-molecule protein sequencing on an integrated semiconductor device ». Science 378, no 6616 (14 octobre 2022) : 186–92. http://dx.doi.org/10.1126/science.abo7651.
Texte intégralRésumé :
Studies of the proteome would benefit greatly from methods to directly sequence and digitally quantify proteins and detect posttranslational modifications with single-molecule sensitivity. Here, we demonstrate single-molecule protein sequencing using a dynamic approach in which single peptides are probed in real time by a mixture of dye-labeled N-terminal amino acid recognizers and simultaneously cleaved by aminopeptidases. We annotate amino acids and identify the peptide sequence by measuring fluorescence intensity, lifetime, and binding kinetics on an integrated semiconductor chip. Our results demonstrate the kinetic principles that allow recognizers to identify multiple amino acids in an information-rich manner that enables discrimination of single amino acid substitutions and posttranslational modifications. With further development, we anticipate that this approach will offer a sensitive, scalable, and accessible platform for single-molecule proteomic studies and applications.
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Malo, Mackenzie E., et Larry Fliegel. « Physiological role and regulation of the Na+/H+ exchanger ». Canadian Journal of Physiology and Pharmacology 84, no 11 (novembre 2006) : 1081–95. http://dx.doi.org/10.1139/y06-065.
Texte intégralRésumé :
In mammalian eukaryotic cells, the Na+/H+ exchanger is a family of membrane proteins that regulates ions fluxes across membranes. Plasma membrane isoforms of this protein extrude 1 intracellular proton in exchange for 1 extracellular sodium. The family of Na+/H+ exchangers (NHEs) consists of 9 known isoforms, NHE1–NHE9. The NHE1 isoform was the first discovered, is the best characterized, and exists on the plasma membrane of all mammalian cells. It contains an N-terminal 500 amino acid membrane domain that transports ions, plus a 315 amino acid C-terminal, the intracellular regulatory domain. The Na+/H+ exchanger is regulated by both post-translational modifications including protein kinase-mediated phosphorylation, plus by a number of regulatory-binding proteins including phosphatidylinositol-4,5-bisphosphate, calcineurin homologous protein, ezrin, radixin and moesin, calmodulin, carbonic anhydrase II, and tescalcin. The Na+/H+ exchanger is involved in a variety of complex physiological and pathological events that include regulation of intracellular pH, cell movement, heart disease, and cancer. This review summarizes recent advances in the understanding of the physiological role and regulation of this protein.
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Wu, Si, Roslyn N. Brown, Samuel H. Payne, Da Meng, Rui Zhao, Nikola Tolić, Li Cao et al. « Top-Down Characterization of the Post-Translationally Modified Intact Periplasmic Proteome from the Bacterium Novosphingobium aromaticivorans ». International Journal of Proteomics 2013 (10 mars 2013) : 1–10. http://dx.doi.org/10.1155/2013/279590.
Texte intégralRésumé :
The periplasm of Gram-negative bacteria is a dynamic and physiologically important subcellular compartment where the constant exposure to potential environmental insults amplifies the need for proper protein folding and modifications. Top-down proteomics analysis of the periplasmic fraction at the intact protein level provides unrestricted characterization and annotation of the periplasmic proteome, including the post-translational modifications (PTMs) on these proteins. Here, we used single-dimension ultra-high pressure liquid chromatography coupled with the Fourier transform mass spectrometry (FTMS) to investigate the intact periplasmic proteome of Novosphingobium aromaticivorans. Our top-down analysis provided the confident identification of 55 proteins in the periplasm and characterized their PTMs including signal peptide removal, N-terminal methionine excision, acetylation, glutathionylation, pyroglutamate, and disulfide bond formation. This study provides the first experimental evidence for the expression and periplasmic localization of many hypothetical and uncharacterized proteins and the first unrestrictive, large-scale data on PTMs in the bacterial periplasm.
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Jung, Gwanghyun, Jing Wang, Pawel Wlodarski, Barbara Barylko, Derk D. Binns, Hongjun Shu, Helen L. Yin et Joseph P. Albanesi. « Molecular determinants of activation and membrane targeting of phosphoinositol 4-kinase IIβ ». Biochemical Journal 409, no 2 (21 décembre 2007) : 501–9. http://dx.doi.org/10.1042/bj20070821.
Texte intégralRésumé :
Mammalian cells contain two isoforms of the type II PI4K (phosphoinositol 4-kinase), PI4KIIα and β. These 55 kDa proteins have highly diverse N-terminal regions (approximately residues 1–90) but conserved catalytic domains (approximately from residue 91 to the C-termini). Nearly the entire pool of PI4KIIα behaves as an integral membrane protein, in spite of a lack of a transmembrane domain. This integral association with membranes is due to palmitoylation of a cysteine-rich motif, CCPCC, located within the catalytic domain. Although the CCPCC motif is conserved in PI4KIIβ, only 50% of PI4KIIβ is membrane-associated, and approximately half of this pool is only peripherally attached to the membranes. Growth factor stimulation or overexpression of a constitutively active Rac mutant induces the translocation of a portion of cytosolic PI4KIIβ to plasma membrane ruffles and stimulates its activity. Here, we demonstrate that membrane-associated PI4KIIβ undergoes two modifications, palmitoylation and phosphorylation. The cytosolic pool of PI4KIIβ is not palmitoylated and has much lower lipid kinase activity than the membrane-associated kinase. Although only membrane-associated PI4KIIβ is phosphorylated in the unique N-terminal region, this modification apparently does not influence its membrane binding or activity. A series of truncation mutants and α/β chimaeras were generated to identify regions responsible for the isoform-specific behaviour of the kinases. Surprisingly, the C-terminal approx. 160 residues, and not the diverse N-terminal regions, contain the sites that are most important in determining the different solubilities, palmitoylation states and stimulus-dependent redistributions of PI4KIIα and β.
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Preston, George W., et David H. Phillips. « Protein Adductomics : Analytical Developments and Applications in Human Biomonitoring ». Toxics 7, no 2 (25 mai 2019) : 29. http://dx.doi.org/10.3390/toxics7020029.
Texte intégralRésumé :
Proteins contain many sites that are subject to modification by electrophiles. Detection and characterisation of these modifications can give insights into environmental agents and endogenous processes that may be contributing factors to chronic human diseases. An untargeted approach, utilising mass spectrometry to detect modified amino acids or peptides, has been applied to blood proteins haemoglobin and albumin, focusing in particular on the N-terminal valine residue of haemoglobin and the cysteine-34 residue in albumin. Technical developments to firstly detect simultaneously multiple adducts at these sites and then subsequently to identify them are reviewed here. Recent studies in which the methods have been applied to biomonitoring human exposure to environmental toxicants are described. With advances in sensitivity, high-throughput handling of samples and robust quality control, these methods have considerable potential for identifying causes of human chronic disease and of identifying individuals at risk.
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Araki, S., K. Kaibuchi, T. Sasaki, Y. Hata et Y. Takai. « Role of the C-terminal region of smg p25A in its interaction with membranes and the GDP/GTP exchange protein ». Molecular and Cellular Biology 11, no 3 (mars 1991) : 1438–47. http://dx.doi.org/10.1128/mcb.11.3.1438-1447.1991.
Texte intégralRésumé :
smg p25A is a ras p21-like small GTP-binding protein which is implicated in the regulated secretory processes. We have recently found that bovine brain smg p25A is geranylgeranylated at its C-terminal region. In this study, we examined the function(s) of the C-terminal region of smg p25A. Limited proteolysis of bovine brain smg p25A with Achromobacter protease I produced an N-terminal fragment and a C-terminal tail. The Mrs of intact smg p25A, the N-terminal fragment, and the C-terminal tail were estimated to be about 24,000, 20,000, and less than 2,000, respectively, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The N-terminal fragment contained the consensus amino acid sequences for GDP/GTP-binding and GTPase activities and showed these activities with kinetic properties similar to those of the intact protein but did not bind to plasma membranes or phosphatidylserine-linked Affigel under conditions in which the intact protein bound to them. The C-terminal tail neither contained the consensus amino acid sequences for GDP/GTP-binding and GTPase activities nor bound to plasma membranes or phosphatidylserine-linked Affigel. The GDP/GTP exchange protein specific for smg p25A, named GDP dissociation inhibitor (GDI), made a complex with the GDP-bound form of the intact smg p25A at a molar ratio of 1:1 and thereby inhibited its GDP/GTP exchange reaction but neither made a complex with the N-terminal fragment or the C-terminal tail nor affected the GDP/GTP exchange reaction of the N-terminal fragment. We expressed smg p25A in Escherichia coli and purified it to near homogeneity. This bacterial protein was not geranylgeranylated. Bacterial smg p25A did not bind to plasma membranes or phosphatidylserine-linked Affigel. smg p25A GDI neither made a complex with bacterial smg p25A nor affected its GDP/GTP exchange reaction. These results suggest that the N-terminal region of smg p25A has GDP/GTP-binding and GTPase activities but lacks the ability to interact with membranes and smg p25A GDI, that the C-terminal region of smg p25A plays important roles in its interaction with membranes and smg p25A GDI, and that some modifications of the C-terminal region, such as geranylgeranylation, which are absent in bacterial smg p25A, are important for these interactions.