The mechanism of N-terminal acetylation of proteins

N alpha-acetylation is almost exclusively restricted to eukaryotic structural proteins. As a rule it is a post-initiational process, requiring the presence of the enzyme N alpha-acetyltransferase and the acetyl donor acetylcoenzyme A. N alpha-acetyltransferases appear to have a narrow substrate specificity, which is very similar for enzymes from different tissues and species. Amino acids predominantly present at the N terminus of N alpha-acetylated proteins are alanine, serine, and methionine. The occurrence of these residues is apparently a prerequisite for acetylation. The region following these amino acids is also important. If methionine is at the N terminus, the second position is always occupied by a strongly hydrophilic amino acid. Two- and three-dimensional structural characteristics of the protein do not seem to play a major role in N alpha-acetylation. Up to now the exact function for N alpha-acetylation is not known.