Nα-Acetylation of yeast ribosomal proteins and its effect on protein synthesis

Nα-Acetyltransferases (NATs) cause the Nα-acetylation of the majority of eukaryotic proteins during their translation, although the functions of this modification have been largely unexplored. In yeast (Saccharomyces cerevisiae), four NATs have been identified: NatA, NatB, NatC, and NatD. In this study, the Nα-acetylation status of ribosomal protein was analyzed using NAT mutants combined with two-dimensional difference gel electrophoresis (2D-DIGE) and mass spectrometry (MS). A total of 60 ribosomal proteins were identified, of which 17 were Nα-acetylated by NatA, and two by NatB. The Nα-acetylation of two of these, S17 and L23, by NatA was not previously observed. Furthermore, we tested the effect of ribosomal protein Nα-acetylation on protein synthesis using the purified ribosomes from each NAT mutant. It was found that the protein synthesis activities of ribosomes from NatA and NatB mutants were decreased by 27% and 23%, respectively, as compared to that of the normal strain. Furthermore, we have shown that ribosomal protein Nα-acetylation by NatA influences translational fidelity in the presence of paromomycin. These results suggest that ribosomal protein Nα-acetylation is necessary to maintain the ribosome's protein synthesis function.

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