Derepression of synthesis of the aminoacyl-transfer ribonucleic acid synthetases for the branched-chain amino acids of Escherichia coli.
The kinetics of derepression of valyl-, isoleucyl-, and leucyl-transfer ribonucleic acid (tRNA) synthetase formation was examined during valine-, isoleucine-, and leucine-limited growth. When valine was limiting growth, valyl-tRNA synthetase formation was maximally derepressed within 5 min, whereas the rates of synthesis of isoleucyl-, and leucyl-tRNA synthetases were unchanged. Isoleucine-restricted growth caused a maximal derepression of isoleucyl-tRNA synthetase formation in 5 min and derepression of valyl-tRNA synthetase formation in 15 min with no effect on leucyl-tRNA synthetase formation. When leucine was limiting growth, leucyl-tRNA synthetase formation was immediately derepressed, whereas valyl- and isoleucyl-tRNA synthetase formation was unaffected by manipulation of the leucine supply to the cells. These results support our previous findings that valyl-tRNA synthetase formation is subject to multivalent repression control by both isoleucine and valine. In contrast, repression control of iso-leucyl- and leucyl-tRNA synthetase formation is specifically mediated by the supply of the cognate amino acid.
D000604:Amino Acyl-tRNA Synthetases / Q000096:biosynthesis*; D001426:Bacterial Proteins / Q000096:biosynthesis; D002250:Carbon Radioisotopes; D002474:Cell-Free System; D002499:Centrifugation, Density Gradient; D002701:Chloramphenicol / Q000494:pharmacology; D004794:Enzyme Repression; D004926:Escherichia coli / Q000201:enzymology* / Q000378:metabolism; D007532:Isoleucine / Q000378:metabolism; D007930:Leucine / Q000378:metabolism; D012293:Rifampin / Q000494:pharmacology; D014633:Valine / Q000378:metabolism
D001426:Bacterial Proteins; D002250:Carbon Radioisotopes; D007532:Isoleucine; D002701:Chloramphenicol; D000604:Amino Acyl-tRNA Synthetases; D007930:Leucine; D014633:Valine; D012293:Rifampin