NH2-terminal acetylation of ribosomal proteins of Saccharomyces cerevisiae.

Using a mutant of Saccharomyces cerevisiae defective in the NAT1 gene, that encodes one of the NH2-terminal acetyltransferases, we have identified 14 ribosomal proteins whose electrophoretic mobility at pH 5.0 suggests they carry an additional charge, presumably due to the lack of NH2-terminal acetylation. At least 30 other ribosomal proteins from the mutant are electrophoretically normal. Attempted NH2-terminal analysis of most of the presumed acetylated proteins from wild type cells indicated that all were blocked. NH2-terminal analysis of the same proteins from the nat1 mutant strain yielded unique sequences. Each one carries an NH2-terminal serine. We conclude that these are normally acetylated due to the presence of the NAT1 gene product. It seems surprising that cells whose ribosomes have been altered to this degree grow rather well and synthesize the same spectrum of proteins as do wild type cells (Mullen, J. R., Kayne, P. S., Moerschell, R. P., Tsunasawa, S. Gribskov, M., Sherman, F., and Sternglanz, R. (1989) EMBO J. 8, 2067-2075). Finally, this analysis has provided the first sequence information available for several of the acetylated ribosomal proteins and for one non-acetylated ribosomal protein, which is clearly the product of the MFT1 gene (Garrett, J. M., Singh, K. K., Vonder Haar, R. A., and Emr. S. D. (1991) Mol. Gen. Gen. 225, 483-491).