Sequence requirements for Nalpha-terminal acetylation of yeast proteins by NatA

NatA is the major N-terminal acetyltransferase of the yeast Saccharomyces cerevisiae. In this study, we took advantage of our recent data on N-terminal acetylation of proteins of the yeast protein map to update the list of proteins with known NatA-dependent acetylation status. Furthermore, using the information available on the acetylation status of 100 novel proteins, we re-examined the rules for acetylation by NatA. The results refine our previous knowledge on NatA substrate specificity depending on the N-terminal and penultimate residues. In particular, we found that the acetylation frequencies of Ser-, Thr- and Ala-, the three residues most often acetylated by NatA, are higher than previously reported. In addition, comparison of the N-terminal region of acetylated and non-acetylated proteins revealed differences in amino acid composition that extend over the 25 first amino acid residues: acetylated proteins are characterized by a higher frequency of glutamate and glutamine and a lower frequency of lysine, arginine and histidine. We suggest that the particularities in amino acid composition of the N-terminal region of acetylated proteins facilitate its interaction with the Nat1p subunit of NatA and its guidance to the catalytic subunit Ard1p.