Abstract
The DNA nucleotide sequence of the valS gene encoding valyl-tRNA synthetase of Escherichia coli has been determined. The deduced primary structure of valyl-tRNA synthetase was compared to the primary sequences of the known aminoacyl-tRNA synthetases of yeast and bacteria. Significant homology was detected between valyl-tRNA synthetase of E. coli and other known branched-chain aminoacyl-tRNA synthetases. In pairwise comparisons the highest level of homology was detected between the homologous valyl-tRNA synthetases of yeast and E. coli, with an observed 41% direct identity overall. Comparisons between the valyl- and isoleucyl-tRNA synthetases of E. coli yielded the highest level of homology detected between heterologous enzymes (19.2% direct identity overall). An alignment is presented between the three branched-chain aminoacyl-tRNA synthetases (valyl- and isoleucyl-tRNA synthetases of E. coli and yeast mitochondrial leucyl-tRNA synthetase) illustrating the close relatedness of these enzymes. These results give credence to the supposition that the branched-chain aminoacyl-tRNA synthetases along with methionyl-tRNA synthetase form a family of genes within the aminoacyl-tRNA synthetases that evolved from a common ancestral progenitor gene.
Highlights
RESULTSAmino acid compositions are in close agreement they both differ markedly from the previously determined amino acid
From the Department of Microbiology and Molecular Genetics, California Collegeof Medicine, Universityof California, Irvine, Irvine, California92717
While some individual size differences may possibly be ascribed to additional domains which serve functions other than those immediately required for the catalysis of tRNA aminoacylation, such as subunitsubunitinteraction (3), autoregulatory functions (4, 5), or protein folding and t-RNA conformation constraint domains (6), the fact that only limited primary sequence homology is observed in pairwise comparisons of the amino acid sequences
Summary
Amino acid compositions are in close agreement they both differ markedly from the previously determined amino acid. Series of sequential deletion derivatives spanning both strands While there is the hint of an internal repeat element within of the DNA encoding valyl-tRNA synthetase (9).The nucleotide sequences of these valS gene M13 deletion derivatives were determined by the method of Sanger et al (8).The sequencing strategy employed illustrates that the nucleotide the valS deduced primary structure (at amino acid residues 328-343 and from 924 to 939, Fig. 2), the fact that there are no significant repeat units within this and other large aminoacyl-tRNA synthetases strongly argues that these polypepsequence was independently obtained for both strands of the tides did not arise from a gene duplication/fusion event (23). Met G l uL y s Thr T y rA s nP roGlnAsp Ile G l uG l nP r oL e uT y rG l uH i sT r pG l uL y sG l nG l yT y rP h eL y sP r oA s "G l yA s pG l u
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
