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The action of N-terminal acetyltransferases on yeast ribosomal proteins.

Arnold R.J., Polevoda B., Reilly J.P., Sherman F.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was used to determine the state of N-terminal acetylation of 68 ribosomal proteins from a normal strain of Saccharomyces cerevisiae and from the ard1-Delta, nat3-Delta, and mak3-Delta mutants (), each lacking a catalytic subunit of three different N-terminal acetyltransferases. A total 30 of the of 68 ribosomal proteins were N-terminal-acetylated, and 24 of these (80%) were NatA substrates, unacetylated in solely the ard1-Delta mutant and having mainly Ac-Ser- termini and a few with Ac-Ala- or Ac-Thr-termini. Only 4 (13%) were NatB substrates, unacetylated in solely the nat3-Delta mutant, and having Ac-Met-Asp- or Ac-Met-Glu-termini. No NatC substrates were uncovered, e.g. unacetylated in solely mak3-Delta mutants, consistent with finding that none of the ribosomal proteins had Ac-Met-Ile-, Ac-Met-Leu-, or Ac-Met-Phe-termini. Interestingly, two new types of the unusual NatD substrates were uncovered, having either Ac-Ser-Asp-Phe- or Ac-Ser-Asp-Ala-termini that were unacetylated in the ard1-Delta mutant, and only partially acetylated in the mak3-Delta mutant and, for one case, also only partially in the nat3-Delta mutant. We suggest that the acetylation of NatD substrates requires not only Ard1p and Nat1p, but also auxiliary factors that are acetylated by the Mak3p and Nat3p N-terminal acetyltransferases.

J. Biol. Chem. 274:37035-37040(1999) [PubMed] [Europe PMC]