STRUCTURE OF THE YEAST VALYL-TRANSFER RNA-SYNTHETASE GENE (VASI) AND THE HOMOLOGY OF ITS TRANSLATED AMINO-ACID-SEQUENCE WITH ESCHERICHIA-COLI ISOLEUCYL-TRANSFER RNA-SYNTHETASE

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  • 25 May 1987
    • journal article
    • research article
    • Vol. 262  (15) , 7189-7194
Abstract
The VASI gene encoding the valyl-tRNA synthetase from yeast was isolated and sequenced. The gene-derived amino acid sequence of yeast valyl-tRNA synthetase was found to be 23% homologous to the Escherichia coli isoleucyl-tRNA synthetase. This is the highest level of homology reported so far between two distinct aminoacyl-tRNA synthetases and is indicative of an evolutionary relationship between these two molecules. Within these homologous sequences, two functional regions could be recognized: the HIGH region which forms part of the binding site of ATP and the KMSKS region which is recognized as the consensus sequence for the binding of the 3''-end of tRNA (Hountondji, C., Dessen, Ph., and Blanquet, S. (1986) Biochemie (Paris) 68, 1071-1078). Secondary structure predictions as well as the presence of both HIGH and KMSKS regions, delireating the nucleotide-binding domain and the COOH-terminal helical domain in aminoacyl-tRNA synthetases of known three-dimensional structure, suggest that the yeast valyl-tRNA synthetase polypeptide chain can be folded into three domains: an NH2-terminal .alpha.-helical region followed by a nucleotide-binding topology and a COOH-terminal domain composed of .alpha.-helices which probably carries major sites in tRNA binding.