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J Bacteriol. 1974 February; 117(2): 449-455
Copyright © 1974 American Society for Microbiology. All Rights Reserved.

Derepressed Levels of the Isoleucine-Valine and Leucine Enzymes in hisT1504, a Strain of Salmonella typhimurium with Altered Leucine Transfer Ribonucleic Acid

¹ Department of Biochemistry, State University of New York, Stony Brook, New York 11790

ABSTRACT

A hisT mutant of Salmonella typhimurium was found to have altered regulation of the isoleucine-valine and leucine enzymes. These enzymes in the hisT strain were derepressed two- to eightfold over those of the parent wild-type strain when grown in minimal medium or under repressing conditions. The amount of tRNA^Leu and the cellular concentration of charged tRNA^Leu was about the same in the hisT strain and in the wild type. However, leucyl-tRNA from the mutant was chromatographically different from that of wild type, confirming previous reports that hisT strains have altered tRNA^Leu. These results suggest strongly that tRNA^Leu is involved in repression of the isoleucine-valine and leucine enzymes in S. typhimurium.