Modification of proteins extends the range of possible molecular structures beyond the limits imposed by the 20 encoded amino acids and, if reversible, gives a means of control and signaling. Many proteins are acetylated, both co-and post-translationally, and at least for eukaryotic proteins, acetylation is the most common covalent modification out of over 200 types that have been reported. Acetylation of proteins is catalyzed by a wide range of acetyltransferases that transfer acetyl groups from acetyl-coenzyme A to either the α-amino group of amino-terminal residues or to the ε-amino group of lysine residues at various positions. (The α-amino group designates the position of the central carbon atom of amino acids, whereas the ε-amino group of lysine residues designates the position of a carbon atom in the side chain.) As shown in Table , amino-terminal acetylation occurs co-translationally on the bulk of acetylated eukaryotic proteins [1
] and post-translationally on prokaryotic ribosomal proteins [4
] and on processed eukaryotic regulatory peptides [6
]. Amino-terminal acetylation is one of the most common protein modifications in eukaryotes, occurring on approximately 85% of eukaryotic proteins, but is rare for prokaryotic proteins [1
]. Furthermore, ε-lysine acetylation occurs post-translationally on histones, high mobility group (HMG) proteins, transcription factors, nuclear receptors [7
], and α-tubulin [10
]. Acetylation affects many protein functions, including enzymatic activity, stability, DNA binding, protein-protein interaction, and peptide-receptor recognition, and occurs on numerous and diverse proteins.
Acetylated proteins and the corresponding acetyltransferases that act either cotranslationally (Co) or post-translationally (Post)