N-alpha-acetyltransferase that specifically mediates the acetylation of N-terminal residues. Able to mediate acetylation of a wide variety of N-terminal residues, with preference for hydrophobic N-termini. Acetylates GroS/GroES and GroEL1. Able to acetylate the ribosomal protein S18, but it is unclear whether it acetylates its N-terminal alanine residue. 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] acetyl-CoA + N-terminal glycyl-[protein] = CoA + H(+) + N-terminal N(alpha)-acetylglycyl-[protein] acetyl-CoA + N-terminal L-alanyl-[protein] = CoA + H(+) + N-terminal N(alpha)-acetyl-L-alanyl-[protein] acetyl-CoA + N-terminal L-seryl-[protein] = CoA + H(+) + N-terminal N(alpha)-acetyl-L-seryl-[protein] acetyl-CoA + N-terminal L-valyl-[protein] = CoA + H(+) + N-terminal N(alpha)-acetyl-L-valyl-[protein] acetyl-CoA + N-terminal L-cysteinyl-[protein] = CoA + H(+) + N-terminal N(alpha)-acetyl-L-cysteinyl-[protein] acetyl-CoA + N-terminal L-threonyl-[protein] = CoA + H(+) + N-terminal N(alpha)-acetyl-L-threonyl-[protein] Monomer (PubMed:27353550). Interacts with TsaD (PubMed:27353550). Interacts with GroS/GroES (PubMed:27353550). Belongs to the acetyltransferase family. RimI subfamily.