Nα-terminal Acetylation of Eukaryotic Proteins (2000)

NH2-terminal, Nα-terminal N-terminal acetyltransferase The two cotranslational processes, cleavage of N-terminal methionine residues and N-terminal1 acetylation, are by far the most common modifications, occurring on the vast majority of eukaryotic proteins. Studies with the yeast Saccharomyces cerevisiae revealed three N-terminal acetyltransferases, NatA, NatB, and NatC, that acted on groups of substrates, each containing degenerate motifs. Orthologous genes encoding the three N-terminal acetyltransferases and the patterns of N-terminal acetylation suggest that eukaryotes generally use the same systems for N-terminal acetylation. The biological significance of this N-terminal modification varies with the particular protein, with some proteins requiring acetylation for function, whereas others do not. Cleavage of N-terminal methionine residues is by far the most common modification, occurring on the vast majority of proteins. Proteins from prokaryotes, mitochondria, and chloroplasts initiate with formylmethionine, whereas proteins from the cytosol of eukaryotes initiate with methionine. The formyl group is usually removed from prokaryotic proteins by a deformylase, resulting in methionine at N termini. The methionine at N termini is cleaved from nascent chains of most prokaryotic and eukaryotic proteins. Results with altered iso-1-cytochromes c from yeast (1Tsunasawa S. Stewart J.W. Sherman F. J. Biol. Chem. 1985; 260: 5382-5391Abstract Full Text PDF PubMed Google Scholar) were the basis for the hypothesis that methionine is cleaved from penultimate residues having radii of gyration of 1.29 Å or less (glycine, alanine, serine, cysteine, threonine, proline, and valine) (2Sherman F. Stewart J.W. Tsunasawa S. Bioessays. 1985; 3: 27-31Crossref PubMed Scopus (230) Google Scholar), a hypothesis that was confirmed from the results of a complete set of altered iso-1 having all possible amino acids at the penultimate position (3Moerschell R.P. Hosokawa Y. Tsunasawa S. Sherman F. J. Biol. Chem. 1990; 265: 19638-19643Abstract Full Text PDF PubMed Google Scholar). A similar pattern of cleavage also was observed with prokaryotic systems in vivo (4Hirel H-P. Schmitter J-M. Dessen P. Fayat G. Blanquet S. Proc. Natl. Acad. Sci. U. S. A. 1989; 86: 8247-8251Crossref PubMed Scopus (668) Google Scholar, 5Dalbı̈ge H. Bayen S. Pedersen J. FEBS Lett. 1990; 266: 1-3Crossref PubMed Scopus (71) Google Scholar) and in vitro (6Ben-Bassat A. Bauer K. Chang S.Y. Myambo K. Boosman A. Chang S. J. Bacteriol. 1987; 169: 751-757Crossref PubMed Google Scholar, 7Wingfield P. Graber P. Turcatti G. Movva N.R. Pelletier M. Craig S. Rose K. Miller C.G. Eur. J. Biochem. 1989; 180: 23-32Crossref PubMed Scopus (32) Google Scholar), and other eukaryotic systems in vivo (8Huang S. Elliott R.C. Liu P.S. Koduri R.K. Weickmann J.L. Lee J.H. Blair L.C. Gosh-Dastidar P. Bradshaw R.A. Bryan K.M. Einarson B. Kendall R.L. Kolacs K.H. Saito K. Biochemistry. 1987; 26: 8242-8246Crossref PubMed Scopus (151) Google Scholar, 9Boissel J.P. Kasper T.J. Bunn H.F. J. Biol. Chem. 1988; 263: 8443-8449Abstract Full Text PDF PubMed Google Scholar) and in vitro (10Chang Y.-H. Teichert U. Smith J.A. J. Biol. Chem. 1990; 265: 19892-19897Abstract Full Text PDF PubMed Google Scholar). Only minor differences were observed between the quantitative results obtained in vivo with yeast iso-1-cytochrome cand with the two proteins, TimJp and TimLp, from Escherichia coli (3Moerschell R.P. Hosokawa Y. Tsunasawa S. Sherman F. J. Biol. Chem. 1990; 265: 19638-19643Abstract Full Text PDF PubMed Google Scholar, 4Hirel H-P. Schmitter J-M. Dessen P. Fayat G. Blanquet S. Proc. Natl. Acad. Sci. U. S. A. 1989; 86: 8247-8251Crossref PubMed Scopus (668) Google Scholar, 5Dalbı̈ge H. Bayen S. Pedersen J. FEBS Lett. 1990; 266: 1-3Crossref PubMed Scopus (71) Google Scholar). The lack of action of methionine aminopeptidase on proteins with large penultimate residues can now be explained by steric hindrance, as deduced from the high resolution crystal structure of the inhibitor complex of methionine aminopeptidase from E. coli(11Lowther W.T. Orville A.M. Madden D.T. Lim S. Rich D.H. Matthews B.W. Biochemistry. 1999; 38: 7678-7688Crossref PubMed Scopus (137) Google Scholar). However, N-terminal methionine is completely or partially retained on certain exceptional proteins having penultimate residues with intermediate sizes of side chains. The mature forms of the S27A, S27B, and L42B ribosomal proteins have Met-Val-Leu or Met-Val-Asn terminal regions (12Arnold R. Polevoda B. Reilly J.P. Sherman F. J. Biol. Chem. 1999; 274: 37035-37040Abstract Full Text Full Text PDF PubMed Scopus (74) Google Scholar). Furthermore, Moerschell et al. (3Moerschell R.P. Hosokawa Y. Tsunasawa S. Sherman F. J. Biol. Chem. 1990; 265: 19638-19643Abstract Full Text PDF PubMed Google Scholar) demonstrated antepenultimate (the third residue) proline residues can inhibit methionine cleavage from certain residues with intermediate sizes of side chains. Also, methionine cleavage was completely inhibited from the Met-Val-Pro sequence of a mutant human hemoglobin (13Prchal J.T. Cashman D.P. Kan Y.W. Proc. Natl. Acad. Sci. U. S. A. 1986; 83: 24-27Crossref PubMed Scopus (32) Google Scholar). In other studies with E. coli, antepenultimate proline residues partially inhibited cleavage from Met-Ala-Pro (4Hirel H-P. Schmitter J-M. Dessen P. Fayat G. Blanquet S. Proc. Natl. Acad. Sci. U. S. A. 1989; 86: 8247-8251Crossref PubMed Scopus (668) Google Scholar, 14Yamada T. Kato K. Kawahara K. Nishimura O. Biochem. Biophys. Res. Commun. 1986; 135: 837-843Crossref PubMed Scopus (39) Google Scholar) and Met-Thr-Pro (15Devlin P.E. Drummond R.J. Toy P. Mark D.F. Watt K.W. Devlin J.J. Gene ( Amst. ). 1988; 65: 13-22Crossref PubMed Scopus (43) Google Scholar). Methionine excision occurs before completion of the nascent chain and before other N-terminal processing events, such as N-terminal acetylation (16Driessen H.P. de Jong W.W. Tesser G.I. Bloemendal H. CRC Crit. Rev. Biochem. 1985; 18: 281-325Crossref PubMed Scopus (180) Google Scholar, 17Kendall R.L. Yamada R. Bradshaw R.A. Methods Enzymol. 1990; 185: 398-407Crossref PubMed Scopus (49) Google Scholar). S. cerevisiae contains two types of methionine aminopeptidases, Map1p and Map2p (18Li X. Chang Y.-H. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 12357-12361Crossref PubMed Scopus (256) Google Scholar). Mutants containing either map1 or map2 null mutations are viable, but the map1 map2 double mutants are nonviable (18Li X. Chang Y.-H. Proc. Natl. Acad. Sci. U. S. A. 1995; 92: 12357-12361Crossref PubMed Scopus (256) Google Scholar). Thus, removal of N-terminal methionine is an essential function in yeast, as in prokaryotes, but the process can be carried out by either of two enzymes. There are probably a number of reasons why N-terminal methionine removal is required for viability. For example,N-myristoylation is essential for growth, andN-myristoyltransferase requires a free N-terminal glycine (19Towler D.A. Eubanks S.R. Towery D.S. Adams S.P. Glaser L. J. Biol. Chem. 1987; 262: 1030-1036Abstract Full Text PDF PubMed Google Scholar). Also, N-terminal residues can be important for the activity of a variety of diverse proteins, such as actin (20Abe A. Saeki K. Yasunaga T. Wakabayashi T. Biochem. Biophys. Res. Commun. 2000; 268: 14-19Crossref PubMed Scopus (44) Google Scholar, 21Hansen J.E. Marner J. Pavlov D. Rubenstein P.A. Reisler E. Biochemistry. 2000; 39: 1792-1799Crossref PubMed Scopus (11) Google Scholar) and proteasome subunits (22Arendt C.S. Hochstrasser M. EMBO J. 1999; 18: 3575-3585Crossref PubMed Scopus (130) Google Scholar, 23Groll M. Heinemeyer W. Jager S. Ullrich T. Bochtler M. Wolf D.H. Huber R. Proc. Natl. Acad. Sci. U. S. A. 1999; 96: 10976-10983Crossref PubMed Scopus (241) Google Scholar). N-terminal acetylation of proteins is catalyzed by NATs that transfer acetyl groups from acetyl-CoA to termini of α-amino groups. Similar to N-terminal methionine cleavage, N-terminal acetylation is one of the most common protein modifications in eukaryotes, occurring on approximately 85% of the different varieties of eukaryotic proteins but rarely on prokaryotic proteins (16Driessen H.P. de Jong W.W. Tesser G.I. Bloemendal H. CRC Crit. Rev. Biochem. 1985; 18: 281-325Crossref PubMed Scopus (180) Google Scholar). In vitro studies indicated that N-terminal acetylation of eukaryotic proteins occurs cotranslationally when there are between 20 and 50 residues extruding from the ribosome (16Driessen H.P. de Jong W.W. Tesser G.I. Bloemendal H. CRC Crit. Rev. Biochem. 1985; 18: 281-325Crossref PubMed Scopus (180) Google Scholar, 17Kendall R.L. Yamada R. Bradshaw R.A. Methods Enzymol. 1990; 185: 398-407Crossref PubMed Scopus (49) Google Scholar). N-terminal acetylation also can occur at internal sites after specific proteolytic processing of the completely translated protein, as in the cases of peptide hormones (24Dores R.M. McDonald L.K. Steveson T.C. Sei C.A. Brain Behav. Evol. 1990; 36: 80-99Crossref PubMed Scopus (57) Google Scholar). Posttranslational acetylation of each of the different proteins occurs with different NATs having different specificities, and these differ from the set of NATs carrying out cotranslational acetylation. Interestingly, internal threonine residues were acetylated when the propeptide region of several proteasome subunits was replaced by a ubiquitin sequence (22Arendt C.S. Hochstrasser M. EMBO J. 1999; 18: 3575-3585Crossref PubMed Scopus (130) Google Scholar). When such artificial protein fusions are expressed in yeast, ubiquitin is rapidly cleaved by deubiquitinating enzymes, presumably on the growing nascent chain, and N termini can serve as substrates for co-translational acetylation. On the other hand, after translation of normal mRNA containing the propeptide region and after near completion of proteasome assembly, subunits are processed at a conserved Gly-Thr motif, exposing the catalytic N-terminal Thr residues, which are not acetylated. Thus, in this instance N-terminal acetylation did not occur when the appropriate N-terminus was formed posttranslationally. Furthermore, artificial constructs with a Met-Thr terminus have the expected cleavage of methionine and N-terminal acetylation of the penultimate threonine residue, resulting in the lack of function. Eukaryotic proteins susceptible to N-terminal acetylation have a variety of different N-terminal sequences with no simple consensus motifs and with no dependence on a single type of residue. Eukaryotic proteins with serine and alanine termini are the most frequently acetylated, and these residues along with methionine, glycine, and threonine account for over 95% of the N-terminal acetylated residues (16Driessen H.P. de Jong W.W. Tesser G.I. Bloemendal H. CRC Crit. Rev. Biochem. 1985; 18: 281-325Crossref PubMed Scopus (180) Google Scholar, 17Kendall R.L. Yamada R. Bradshaw R.A. Methods Enzymol. 1990; 185: 398-407Crossref PubMed Scopus (49) Google Scholar, 25Bradshaw R.A. Brickey W.W. Walker K.W. Trends Biochem. Sci. 1998; 23: 263-267Abstract Full Text Full Text PDF PubMed Scopus (411) Google Scholar, 26Persson B. Flinta C. von Heijne G. Jörnvall H. Eur. J. Biochem. 1985; 152: 523-527Crossref PubMed Scopus (154) Google Scholar). However, only subsets of proteins with any of these N-terminal residues are acetylated, and none of these N-terminal residues guarantee acetylation. Ard1p, Nat3p, and Mak3p are related to each other by amino acid sequence and are believed to be the catalytic subunits of three different NATs, designated NatA, NatB, and NatC, respectively, each acting on different sets of proteins having different N-terminal regions (27Polevoda B. Norbeck J. Takakura H. Blomberg A. Sherman F. EMBO J. 1999; 18: 6155-6168Crossref PubMed Scopus (174) Google Scholar, 28Tercero J.C. Wickner R.B. J. Biol. Chem. 1992; 267: 20277-20281Abstract Full Text PDF PubMed Google Scholar, 29Tercero J.C. Riles L.E. Wickner R.B. J. Biol. Chem. 1992; 267: 20270-20276Abstract Full Text PDF PubMed Google Scholar) (Fig. 1). Ard1p activity requires two subunits, Ard1p itself and Nat1p. Anat1 − mutant was originally uncovered by screening a collection of heavily mutagenized strains for protein acetyltransferase activity in vitro (30Mullen J.R. Kayne P.S. Moerschell R.P. Tsunasawa S. Gribskov M. Colavito-Shepanski M. Grunstein M. Sherman F. Sternglanz R. EMBO J. 1989; 8: 2067-2075Crossref PubMed Scopus (245) Google Scholar). The previously identified ard1 − mutant was first suspected to be related to nat1 − because of certain similar phenotypes (30Mullen J.R. Kayne P.S. Moerschell R.P. Tsunasawa S. Gribskov M. Colavito-Shepanski M. Grunstein M. Sherman F. Sternglanz R. EMBO J. 1989; 8: 2067-2075Crossref PubMed Scopus (245) Google Scholar). Overexpression of both Ard1p and Nat1p subunits is required for increased NAT activity in vivo (30Mullen J.R. Kayne P.S. Moerschell R.P. Tsunasawa S. Gribskov M. Colavito-Shepanski M. Grunstein M. Sherman F. Sternglanz R. EMBO J. 1989; 8: 2067-2075Crossref PubMed Scopus (245) Google Scholar), and both interact with each other to form an active complex in vitro(31Park E.-C. Szostak J.W. EMBO J. 1992; 11: 2087-2093Crossref PubMed Scopus (139) Google Scholar). The MAK3 gene encodes a NAT that is required for the N-terminal acetylation of the killer viral major coat protein,gag, with an Ac-Met-Leu-Arg-Phe terminus. MAK3was first identified from mak3 −-deficient mutants that did not assemble or maintain the L-A double-stranded RNA viral particle (28Tercero J.C. Wickner R.B. J. Biol. Chem. 1992; 267: 20277-20281Abstract Full Text PDF PubMed Google Scholar, 32Tercero J.C. Dinman J.D. Wickner R.B. J. Bacteriol. 1993; 175: 3192-3194Crossref PubMed Scopus (54) Google Scholar). The co-purification of Mak3p, Mak10p, and Mak31p suggests that these three subunits form a complex that is required for N-terminal acetylation (33Rigaut G. Shevchenko A. Rutz B. Wilm M. Mann M. Seraphin B. Nature Biotechnol. 1999; 17: 1030-1032Crossref PubMed Scopus (2287) Google Scholar). Nat3p was originally identified on the basis of similarities of its amino acid sequence to those of Ard1p and Mak3p (27Polevoda B. Norbeck J. Takakura H. Blomberg A. Sherman F. EMBO J. 1999; 18: 6155-6168Crossref PubMed Scopus (174) Google Scholar). Previous attempts to predict N-terminal acetylation based on the properties of amino acid residues distributed along the N-terminal region were unsuccessful (16Driessen H.P. de Jong W.W. Tesser G.I. Bloemendal H. CRC Crit. Rev. Biochem. 1985; 18: 281-325Crossref PubMed Scopus (180) Google Scholar, 26Persson B. Flinta C. von Heijne G. Jörnvall H. Eur. J. Biochem. 1985; 152: 523-527Crossref PubMed Scopus (154) Google Scholar, 34Flinta C. Persson B. Jörnvall H. von Heijne G. Eur. J. Biochem. 1986; 154: 193-196Crossref PubMed Scopus (241) Google Scholar, 35Augen J. Wold F. Trends Biochem. Sci. 1986; 11: 494-497Abstract Full Text PDF Scopus (28) Google Scholar). However, new insights on this problem have been provided by using yeast mutants deleted in one or another of these NAT genes. The substrate specificities for each of the Ard1p, Nat3p, and Mak3p enzymes were deduced from considering the lack of acetylation of the following groups of protein in mutants containing one or another of the ard1-Δ,nat1-Δ, nat3-Δ, or mak3-Δ deletions: mutationally altered iso-1-cytochromes c (27Polevoda B. Norbeck J. Takakura H. Blomberg A. Sherman F. EMBO J. 1999; 18: 6155-6168Crossref PubMed Scopus (174) Google Scholar); mutationally altered β-galactosidases (32Tercero J.C. Dinman J.D. Wickner R.B. J. Bacteriol. 1993; 175: 3192-3194Crossref PubMed Scopus (54) Google Scholar); abundant proteins (27Polevoda B. Norbeck J. Takakura H. Blomberg A. Sherman F. EMBO J. 1999; 18: 6155-6168Crossref PubMed Scopus (174) Google Scholar,36Perrot M. Sagliocco F. Mini T. Monbirot C. Schneider U. Shevchenko A. Mann M. Jeno P. Boucherie H. Electrophoresis. 1999; 20: 2280-2298Crossref PubMed Scopus (118) Google Scholar, 37Garrels J.I. McLaughlin C.S. Warner J.R. Futcher B. Latter G.I. Kobayashi R. Schwender B. Volpe T. Anderson D.S. Mesquita-Fuentes R. Payne W.E. Electrophoresis. 1997; 18: 1347-1360Crossref PubMed Scopus (116) Google Scholar); ribosomal proteins (12Arnold R. Polevoda B. Reilly J.P. Sherman F. J. Biol. Chem. 1999; 274: 37035-37040Abstract Full Text Full Text PDF PubMed Scopus (74) Google Scholar); and 20 S proteasome subunits (38Kimura Y. Takaoka M. Tanaka S. Sassa H. Tanaka K. Polevoda B. Sherman F. Hirano H. J. Biol. Chem. 2000; 275: 4635-4639Abstract Full Text Full Text PDF PubMed Scopus (97) Google Scholar). As summarized in Fig. 1, subclasses of proteins with Ser, Ala, Gly, or Thr termini are not acetylated in ard1-Δ mutants (NatA substrates) (27Polevoda B. Norbeck J. Takakura H. Blomberg A. Sherman F. EMBO J. 1999; 18: 6155-6168Crossref PubMed Scopus (174) Google Scholar); proteins with Met-Glu or Met-Asp termini and subclasses of proteins with Met-Asn termini are not acetylated innat3-Δ mutants (NatB substrates) (27Polevoda B. Norbeck J. Takakura H. Blomberg A. Sherman F. EMBO J. 1999; 18: 6155-6168Crossref PubMed Scopus (174) Google Scholar); and subclasses of proteins with Met-Ile, Met-Leu, Met-Trp, or Met-Phe termini are not acetylated in mak3-Δ mutants (NatC substrates) (27Polevoda B. Norbeck J. Takakura H. Blomberg A. Sherman F. EMBO J. 1999; 18: 6155-6168Crossref PubMed Scopus (174) Google Scholar, 32Tercero J.C. Dinman J.D. Wickner R.B. J. Bacteriol. 1993; 175: 3192-3194Crossref PubMed Scopus (54) Google Scholar,38Kimura Y. Takaoka M. Tanaka S. Sassa H. Tanaka K. Polevoda B. Sherman F. Hirano H. J. Biol. Chem. 2000; 275: 4635-4639Abstract Full Text Full Text PDF PubMed Scopus (97) Google Scholar). In addition, a special subclass of NatA substrates with Ser-Glu, Ser-Asp, Ala-Glu, or Gly-Glu termini, designated NatD substrates, is also only partially acetylated in nat3-Δ andmak3-Δ mutants (Table I, Fig. 1) (12Arnold R. Polevoda B. Reilly J.P. Sherman F. J. Biol. Chem. 1999; 274: 37035-37040Abstract Full Text Full Text PDF PubMed Scopus (74) Google Scholar, 27Polevoda B. Norbeck J. Takakura H. Blomberg A. Sherman F. EMBO J. 1999; 18: 6155-6168Crossref PubMed Scopus (174) Google Scholar).Table IExamples of N-terminal acetylation of NatD and other substratesApproximate acetylationNatANatBNatCTypeGeneSequenceNormalard1, nat1nat3mak3Ref.%%%%CYC1–795Thr-Glu-Phe-Leu-Ala-027Polevoda B. Norbeck J. Takakura H. Blomberg A. Sherman F. EMBO J. 1999; 18: 6155-6168Crossref PubMed Scopus (174) Google ScholarNatACYC1–1383Ac-Ser-Glu-Ile-Thr-Ala-10001001001-aB. Polevoda and F. Sherman, unpublished result.NatBCYC1–853Ac-Met-Glu-Phe-Leu-Ala-100100010027Polevoda B. Norbeck J. Takakura H. Blomberg A. Sherman F. EMBO J. 1999; 18: 6155-6168Crossref PubMed Scopus (174) Google ScholarNatCCYC1–1162Ac-Met-Ile-Arg-Leu-Lys-94100100027Polevoda B. Norbeck J. Takakura H. Blomberg A. Sherman F. EMBO J. 1999; 18: 6155-6168Crossref PubMed Scopus (174) Google ScholarNatDCYC1–963Ac-Gly-Glu-Phe-Leu-Ala-100050601-bThe percent N-terminal acetylation was determined by mass spectrometry (B. Polevoda and F. Sherman, unpublished result), correcting the values determined earlier by HPLC (27).CYC1–962Ac-Ala-Glu-Phe-Leu-Ala-100010401-bThe percent N-terminal acetylation was determined by mass spectrometry (B. Polevoda and F. Sherman, unpublished result), correcting the values determined earlier by HPLC (27).RPS20Ac-Ser-Asp-Phe-Gln-Lys-1000906012Arnold R. Polevoda B. Reilly J.P. Sherman F. J. Biol. Chem. 1999; 274: 37035-37040Abstract Full Text Full Text PDF PubMed Scopus (74) Google ScholarRPS24AAc-Ser-Asp-Ala-Val-Thr-100010040121-a B. Polevoda and F. Sherman, unpublished result.1-b The percent N-terminal acetylation was determined by mass spectrometry (B. Polevoda and F. Sherman, unpublished result), correcting the values determined earlier by HPLC (27Polevoda B. Norbeck J. Takakura H. Blomberg A. Sherman F. EMBO J. 1999; 18: 6155-6168Crossref PubMed Scopus (174) Google Scholar). Open table in a new tab One possible interpretation of the NatD substrates is that they are a subclass of NatA substrates requiring, in addition to Ard1p and Nat1p, other factors whose full active form requires acetylation by Mak3p and Nat3p. The lack of acetylation of the auxiliary factors may in no or only acetylation, on the particular NatD as summarized in acetylation be from the amino acid Only the substrates have common sequences that can be and these are of and probably As by Moerschell et al. (3Moerschell R.P. Hosokawa Y. Tsunasawa S. Sherman F. J. Biol. Chem. 1990; 265: 19638-19643Abstract Full Text PDF PubMed Google Scholar), all eukaryotic Met-Glu and Met-Asp proteins uncovered in and were acetylated, but not any of the prokaryotic proteins with the same terminal Furthermore, all normal yeast proteins having Met-Glu and Met-Asp were acetylated (3Moerschell R.P. Hosokawa Y. Tsunasawa S. Sherman F. J. Biol. Chem. 1990; 265: 19638-19643Abstract Full Text PDF PubMed Google Scholar, R. Polevoda B. Reilly J.P. Sherman F. J. Biol. Chem. 1999; 274: 37035-37040Abstract Full Text Full Text PDF PubMed Scopus (74) Google Scholar, 27Polevoda B. Norbeck J. Takakura H. Blomberg A. Sherman F. EMBO J. 1999; 18: 6155-6168Crossref PubMed Scopus (174) Google Scholar, 32Tercero J.C. Dinman J.D. Wickner R.B. J. Bacteriol. 1993; 175: 3192-3194Crossref PubMed Scopus (54) Google Scholar). However, there are Met-Glu and Met-Asp iso-1-cytochromes c with of acetylation, and (Table suggest that all the substrates any one of these required but acetylation is by For from the with the iso-1 having only acetylation, one can suggest that proline residues the action of Nat3p. Moerschell et al. (3Moerschell R.P. Hosokawa Y. Tsunasawa S. Sherman F. J. Biol. Chem. 1990; 265: 19638-19643Abstract Full Text PDF PubMed Google Scholar) demonstrated that antepenultimate proline residues can inhibit methionine cleavage from certain of similar sequences that are partially or not acetylation values are that to be with acetylation are certain residues that to be required for acetylation are in The acetylation values are that to be with acetylation are certain residues that to be required for acetylation are in of the N-terminal region of NatD substrates and related sequences an but not for residues, or at the antepenultimate position suggest that NATs on substrates with specific but degenerate sequences and that the can be by suggest that acetylation can be by the residues on the nascent chain at the of this Thus, the of acetylation is the of or residues and Furthermore, this lack of acetylation be because of the of required residues or the of For the antepenultimate residue, in sequence can be complete acetylation, whereas the antepenultimate residue, in the sequence can be resulting in only acetylation (Table On the other hand, the antepenultimate residues, in sequence acetylation because is not of a required the other of the in the sequence and the in the can be the of required and residues are the of a protein to be acetylated be from the Also, is an amino acid position is by required or For in the by the L-A and proteins (Table is the is of the required sequence or residues the action of the of substrates and related proteins are also in The NatA substrates to be the most a of those with N-terminal residues of serine or In approximately and of the and proteins, respectively, are acetylated (16Driessen H.P. de Jong W.W. Tesser G.I. Bloemendal H. CRC Crit. Rev. Biochem. 1985; 18: 281-325Crossref PubMed Scopus (180) Google Scholar). of related acetylated and proteins having serine, alanine, or threonine termini are in the for the lack of acetylation of most of these proteins is the N-terminal region of of the proteins related to both NatA and substrates contains residues, and as as proline residues, whereas some proteins related to substrates residues, such as but not the c is acetylated (Table one can suggest that residues sites amino acid residues from the terminus. the required and residues may acetylation to and because residues may sites in the nascent chain, acetylated and sequences is The that N-terminal acetylation, occurring increased of the action of is the of the biological of this modification S. D.A. PubMed Scopus Google Scholar, S. PubMed Scopus (97) Google Scholar). However, there are the biological of N-terminal acetylation occurring at of acetylation, of J.A. M. J. Biol. PubMed Scopus Google Scholar) and the E. coli ribosomal S protein K. J. Biol. PubMed Scopus Google Scholar). actin from is less in the of the acetylated form G. L. J.L. Biochem. PubMed Scopus Google Scholar). et al. A. H. E. G. Rose Proc. Natl. Acad. Sci. U. S. A. Scholar) observed that c and from were not in in to the from yeast, which were Also, et al. S. M. C. E. T. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar) that N-terminal acetylation c from in be that in these and other the proteins acetylated termini also other differences in amino acid In R. E. et al. E. and C. W. unpublished and nat1 − yeast strains to acetylated and of and yeast respectively, and observed of ubiquitin each both yeast forms were both of the Thus, the in of and yeast is because of differences other N-terminal acetylation. Furthermore, et al. A. N.R. A. 1989; PubMed Scopus Google Scholar) observed of N-terminal acetylated proteins in a A for the of N-terminal acetylation from the in As the are partially − and ard1 to a a In − and ard1 − mutants of of strains to and the to when for (30Mullen J.R. Kayne P.S. Moerschell R.P. Tsunasawa S. Gribskov M. Colavito-Shepanski M. Grunstein M. Sherman F. Sternglanz R. EMBO J. 1989; 8: 2067-2075Crossref PubMed Scopus (245) Google Scholar). these are because of the lack of N-terminal acetylation of one or specific proteins requiring acetylation for function. function by the lack of acetylation of the protein, for can the of A.M. Sternglanz R. Biol. 11: PubMed Scopus Google Scholar), whereas function of any one of a number of proteins in the can the to and the of to (30Mullen J.R. Kayne P.S. Moerschell R.P. Tsunasawa S. Gribskov M. Colavito-Shepanski M. Grunstein M. Sherman F. Sternglanz R. EMBO J. 1989; 8: 2067-2075Crossref PubMed Scopus (245) Google Scholar). Also, as the lack of N-terminal acetylation of the viral major coat protein,gag, in mak3 − strains or of the viral particle (28Tercero J.C. Wickner R.B. J. Biol. Chem. 1992; 267: 20277-20281Abstract Full Text PDF PubMed Google Scholar). − strains do not at probably because of the lack of acetylation of a protein (27Polevoda B. Norbeck J. Takakura H. Blomberg A. Sherman F. EMBO J. 1999; 18: 6155-6168Crossref PubMed Scopus (174) Google Scholar, 28Tercero J.C. Wickner R.B. J. Biol. Chem. 1992; 267: 20277-20281Abstract Full Text PDF PubMed Google Scholar). Similar to the other mutants lack of on at on containing and of the from the lack of acetylation of any of a number of proteins essential for different the proteins for these are not the and be to lack of acetylation of actin which contains a normal N-terminal actin mutants are and which D. 1992; PubMed Google Scholar). Furthermore, actin in the with (20Abe A. Saeki K. Yasunaga T. Wakabayashi T. Biochem. Biophys. Res. Commun. 2000; 268: 14-19Crossref PubMed Scopus (44) Google Scholar). only can the lack of acetylation in but acetylation also can normal The acetylation of the N-terminal catalytic threonine of 20 S proteasome subunits the of specific (22Arendt C.S. Hochstrasser M. EMBO J. 1999; 18: 3575-3585Crossref PubMed Scopus (130) Google Scholar). both N-terminal acetylation and the lack of N-terminal acetylation have to the of specific enzymes. Interestingly, the N-terminal sequence of Mak3p is of a The acetylation of substrates in the nat3-Δ, that acetylation of Mak3p is not required for its function. The of and nat3-Δ mutants NATs suggests that the of acetylation may be and not for most proteins. only a of proteins requires this modification for activity or whereas the is acetylated only because termini to consensus N-terminal acetylation not proteins from as any in of proteins from by the When is the function of N-terminal the function, for of a The in the pattern of N-terminal acetylation of proteins from eukaryotes and S. cerevisiae (3Moerschell R.P. Hosokawa Y. Tsunasawa S. Sherman F. J. Biol. Chem. 1990; 265: 19638-19643Abstract Full Text PDF PubMed Google Scholar) suggests that the same systems may in all Also, genes encoding the three N-terminal acetyltransferases that the same or similar N-terminal acetyltransferases may be in containing of the yeast Ard1p and of the yeast Nat3p D. and H. and of the yeast Mak3p A. Polevoda and F. Sherman, unpublished The of one or another in suggests that the eukaryotic systems for N-terminal acetylation. Wickner and Sternglanz for the