

Department of Molecular Biology, University of Bergen, Bergen, Norway.
PLoS ONE (Impact Factor: 3.73). 01/2011; 6(9):e24713. DOI:10.1371/journal.pone.0024713
Source: PubMed


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    ABSTRACT: N(alpha)-terminal acetylation is one of the most common protein modifications in eukaryotes. The COmbined FRActional DIagonal Chromatography (COFRADIC) proteomics technology that can be specifically used to isolate N-terminal peptides was used to determine the N-terminal acetylation status of 742 human and 379 yeast protein N termini, representing the largest eukaryotic dataset of N-terminal acetylation. The major N-terminal acetyltransferase (NAT), NatA, acts on subclasses of proteins with Ser-, Ala-, Thr-, Gly-, Cys- and Val- N termini. NatA is composed of subunits encoded by yARD1 and yNAT1 in yeast and hARD1 and hNAT1 in humans. A yeast ard1-Delta nat1-Delta strain was phenotypically complemented by hARD1 hNAT1, suggesting that yNatA and hNatA are similar. However, heterologous combinations, hARD1 yNAT1 and yARD1 hNAT1, were not functional in yeast, suggesting significant structural subunit differences between the species. Proteomics of a yeast ard1-Delta nat1-Delta strain expressing hNatA demonstrated that hNatA acts on nearly the same set of yeast proteins as yNatA, further revealing that NatA from humans and yeast have identical or nearly identical specificities. Nevertheless, all NatA substrates in yeast were only partially N-acetylated, whereas the corresponding NatA substrates in HeLa cells were mainly completely N-acetylated. Overall, we observed a higher proportion of N-terminally acetylated proteins in humans (84%) as compared with yeast (57%). N-acetylation occurred on approximately one-half of the human proteins with Met-Lys- termini, but did not occur on yeast proteins with such termini. Thus, although we revealed different N-acetylation patterns in yeast and humans, the major NAT, NatA, acetylates the same substrates in both species.
    Proceedings of the National Academy of Sciences 06/2009; 106(20):8157-62. · 9.74 Impact Factor
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    ABSTRACT: Analysis of soluble Ehrlich ascites proteins by the Sanger procedure revealed methionine, alanine, valine, and glycine as the major NH2-terminal amino acids. The average monomer weights of these proteins calculated from the yields of NH2-terminal amino acids was 144,000. In contrast, the average monomer weight of Ehrlich ascites soluble proteins calculated from the data obtained after electrophoresis in polyacrylamide gels containing sodium dodecyl sulfate was 32,500. The explanation for the disparity in the estimates of average monomer weight obtained by the procedures appears to be that extensive blocking of alpha-NH2 groups by acetate occurs in these proteins, i.e. of the acetate present in the acidic peptides isolated from proteolytic digests of ascites proteins, 23.2 nmol/mg of protein appears to originate from N-acetyl amino acids. These results suggest that approximately 80% of the soluble proteins from Ehrlich ascites cells contain acetate at their NH2-terminal residues. The extensive N-acetylation of proteins does not appear to be limited to Ehrlich ascites cells and may be characteristic of eukaryotic proteins.
    Journal of Biological Chemistry 03/1976; 251(4):1009-14. · 4.65 Impact Factor
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    ABSTRACT: The retained N-terminal methionine (Met) residue of a nascent protein is often N-terminally acetylated (Nt-acetylated). Removal of N-terminal Met by Met-aminopeptidases frequently leads to Nt-acetylation of the resulting N-terminal alanine (Ala), valine (Val), serine (Ser), threonine (Thr), and cysteine (Cys) residues. Although a majority of eukaryotic proteins (for example, more than 80% of human proteins) are cotranslationally Nt-acetylated, the function of this extensively studied modification is largely unknown. Using the yeast Saccharomyces cerevisiae, we found that the Nt-acetylated Met residue could act as a degradation signal (degron), targeted by the Doa10 ubiquitin ligase. Moreover, Doa10 also recognized the Nt-acetylated Ala, Val, Ser, Thr, and Cys residues. Several examined proteins of diverse functions contained these N-terminal degrons, termed AcN-degrons, which are a prevalent class of degradation signals in cellular proteins.
    Science 02/2010; 327(5968):973-7. · 31.20 Impact Factor

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