N‐terminal acetylome analysis reveals the specificity of Naa50 (Nat5) and suggests a kinetic competition between N‐terminal acetyltransferases and methionine aminopeptidases

摘要: Cotranslational N-terminal (Nt-) acetylation of nascent polypeptides is mediated by acetyltransferases (NATs). The very amino acid sequence largely determines whether or not a given protein Nt-acetylated. Currently, there are six distinct NATs characterized, NatA-NatF, in humans which the vivo substrate specificity Naa50 (Nat5)/NatE, an alternative catalytic subunit human NatA, so far remained elusive. In this study, we quantitatively compared Nt-acetylomes wild-type yeast S. cerevisiae expressing endogenous (yNaa50), congenic strain lacking yNaa50, and otherwise identical (hNaa50). Six canonical NatA substrates were Nt-acetylated less yNaa50 than yeast. contrast, ectopically expressed hNaa50 resulted, predominantly, Nt-acetylation Met (iMet) starting N-termini, including iMet-Lys, iMet-Val, iMet-Ala, iMet-Tyr, iMet-Phe, iMet-Leu, iMet-Ser, iMet-Thr N-termini. This identified as being similar, its specificity, to previously characterized hNaa60/NatF. addition, identification, yNaa50-lacking hNaa50, iMet followed small residue such Ser, Thr, Ala, Val, revealed kinetic competition between Met-aminopeptidases (MetAPs), implied that cannot be removed MetAPs, deduction supported our vitro data. As such, Naa50-mediated may act retain proteins MetAP susceptible N-termini fraction retained (followed residue) setting would expected depend on relative levels ribosome-associated Naa50/NatA MetAPs.