N-alpha-acetyltransferase that acetylates the N-terminus of proteins that retain their initiating methionine. Has a broad substrate specificity: able to acetylate the initiator methionine of most peptides, except for those with a proline in second position. Also displays N-epsilon-acetyltransferase activity by mediating acetylation of the side chain of specific lysines on proteins. The relevance of N-epsilon-acetyltransferase activity is however unclear. Required for sister chromatid cohesion during mitosis by promoting binding of CDCA5/sororin to cohesin. acetyl-CoA + N-terminal L-methionyl-L-alanyl-[protein] = CoA + H(+) + N-terminal N(alpha)-acetyl-L-methionyl-L-alanyl-[protein] acetyl-CoA + N-terminal L-methionyl-L-seryl-[protein] = CoA + H(+) + N-terminal N(alpha)-acetyl-L-methionyl-L-seryl-[protein] acetyl-CoA + N-terminal L-methionyl-L-valyl-[protein] = CoA + H(+) + N-terminal N(alpha)-acetyl-L-methionyl-L-valyl-[protein] acetyl-CoA + N-terminal L-methionyl-L-threonyl-[protein] = CoA + H(+) + N-terminal N(alpha)-acetyl-L-methionyl-L-threonyl-[protein] acetyl-CoA + N-terminal L-methionyl-L-lysyl-[protein] = CoA + H(+) + N-terminal N(alpha)-acetyl-L-methionyl-L-lysyl-[protein] acetyl-CoA + N-terminal L-methionyl-L-leucyl-[protein] = CoA + H(+) + N-terminal N(alpha)-acetyl-L-methionyl-L-leucyl-[protein] acetyl-CoA + N-terminal L-methionyl-L-phenylalanyl-[protein] = CoA + H(+) + N-terminal N(alpha)-acetyl-L-methionyl-L-phenylalanyl-[protein] acetyl-CoA + N-terminal L-methionyl-L-tyrosyl-[protein] = CoA + H(+) + N-terminal N(alpha)-acetyl-L-methionyl-L-tyrosyl-[protein] Localizes to the cytoplasm in interphase cells. Belongs to the acetyltransferase family. GNAT subfamily.