N-alpha-acetyltransferase that specifically mediates the acetylation of N-terminal residues of the transmembrane proteins, with a strong preference for N-termini facing the cytosol (PubMed:25732826). Displays N-terminal acetyltransferase activity towards a range of N-terminal sequences including those starting with Met-Lys, Met-Val, Met-Ala and Met-Met (PubMed:21750686, PubMed:25732826, PubMed:27550639, PubMed:27320834). Required for normal chromosomal segregation during anaphase (PubMed:21750686). May also show histone acetyltransferase activity; such results are however unclear in vivo and would require additional experimental evidences (PubMed:21981917). acetyl-CoA + N-terminal L-methionyl-[transmembrane protein] = CoA + H(+) + N-terminal N(alpha)-acetyl-L-methionyl-[transmembrane protein] acetyl-CoA + L-lysyl-[protein] = CoA + H(+) + N(6)-acetyl-L-lysyl-[protein] Monomer and homodimer; monomer in presence of substrate and homodimer in its absence (PubMed:27320834). Probably forms an intramembrane hairpin-like structure in the membrane. Isoform 2: Imprinted (PubMed:21593219). Promoter methylation of the paternal allele may restrict expression to the maternal allele in placenta and leukocytes (PubMed:21593219). Isoform 1: Biallelically expressed (PubMed:21593219). Acetylated: autoacetylation is required for optimal acetyltransferase activity. In placenta and leukocytes, expressed from the maternal allele, due to imprinting of the paternal allele. Produced by alternative splicing. Produced by alternative splicing. Produced by alternative splicing. Belongs to the acetyltransferase family. NAA60 subfamily. According to a report, displays histone acetyltransferase activity while localized in the Golgi apparatus (PubMed:21981917). May mediate acetylation of free histone H4 and promote nucleosome assembly (PubMed:21981917). Such results are however unclear in vivo and recent reports strongly suggest that it acts as a N-alpha-acetyltransferase that specifically targets N-terminal residues of transmembrane proteins (PubMed:21750686, PubMed:25732826).