An yeast nuclear mutation conferring temperature-sensitivity to the mitochondrial tryptophanyl-tRNA synthetase.
The conditional respiratory-deficient Saccharomyces cerevisiae mutant pet-ts2281 was complemented by an yeast genomic DNA library. The gene thus isolated was sequenced and proved to be identical to the known MSW1 sequence encoding mitochondrial tryptophanyl-tRNA synthetase (Myers and Tzagoloff 1985). Compared to the wild-type, the ts2281 mutant allele of MSW1 contained a single T----C transition leading to a Leu----Ser replacement at position 294 of the protein sequence. In addition to this mutational alteration, our sequence data for the wild-type gene differ from the originally published MSW1 sequence at five other DNA positions which affect two locally restricted regions of the polypeptide chain. As expected, at the non-permissive temperature ts2281 cells are specifically defective in mitochondrial trp-tRNA formation and, thus, in overall mitochondrial protein synthesis. In addition, the patterns of cytochrome b mRNA maturation intermediates were distinctly different in ts2281 and wild-type yeast cells. The mutational effect of the observed amino-acid substitution in ts2281 is discussed in terms of weakened hydrogen bonding in the C-terminal half of the MSW1-encoded protein.
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Lehrstuhl für Biochemie, Universität Erlangen-Nürnberg, Federal Republic of Germany.
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Lisowsky
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Schweizer
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D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D008928:Mitochondria / Q000201:enzymology; D008969:Molecular Sequence Data; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D013696:Temperature; D014369:Tryptophan-tRNA Ligase / Q000235:genetics*
D014369:Tryptophan-tRNA Ligase