Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “VALINE”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 829 records · Page 46Linked to original sources
PubMed1984

Synthesis of the isoleucyl- and valyl-tRNA synthetases and the isoleucine-valine biosynthetic enzymes in a threonine deaminase regulatory mutant of Escherichia coli K-12.

A mutation in the structural gene for threonine deaminase, ilvA538 , results in lower than normal levels of the isoleucyl, valyl- and leucyl-tRNA synthetases. Moreover, this regulatory mutation decreases the level of expression of the ilv biosynthetic operons and renders their expression non-responsive to limitations of the branched-chain amino acids. In this paper, we present in vitro evidence for the inhibition of isoleucyl- and valyl-tRNA synthetase activity by threonine deaminase and 2-ketobutyrate, the product of the threonine deaminase reaction, through the formation of a high molecular weight complex of the three molecules. Based on these results, we propose a model to explain the regulation of the isoleucyl- and valyt -tRNA synthetases in which transient inhibition of the synthetase enzyme activities by threonine deaminase and 2-ketobutyrate increases the expression of ileS and valS , the structural genes for isoleucyl- and valyt -tRNA synthetase, respectively. Further, the results suggest that the hyperattenuated expression of the ilv biosynthetic operons is due to an increased rate of complex formation of valyl and isoleucyl-tRNA synthetases and the altered form of threonine deaminase of the ilvA538 mutant strain.

Amino Acyl-tRNA Synthetases↗