title: Regulation of tryptophanyl-tRNA synthetase formation.
abstract: A previously constructed trp-S-lacZ fusion encoding a hybrid protein with beta-galactosidase activity was subcloned from a multicopy plasmid onto a lambda vector. Single-copy lysogens of lambda trpS-lacZ were used to determine whether trpS was regulated in a manner similar to that of other aminoacyl-tRNA synthetases. trpS regulation was found to resemble that of the majority of synthetases, in that expression of the lysogen-encoded hybrid beta-galactosidase varied with growth rate; beta-galactosidase activity increased 2.5-fold as the generation time decreased from 150 to 37 min. This regulatory response was confirmed by DNA/RNA hybridization experiments, which also suggested that this form of metabolic regulation occurred at the transcriptional level. No alteration in the level of hybrid beta-galactosidase was observed, however, when cells were starved for tryptophan.
mesh_terms: D000604:Amino Acyl-tRNA Synthetases / Q000096:biosynthesis*; D004274:DNA, Recombinant; D004926:Escherichia coli / Q000201:enzymology / Q000254:growth & development; D005786:Gene Expression Regulation; D009876:Operon; D014158:Transcription, Genetic; D014364:Tryptophan / Q000378:metabolism; D014369:Tryptophan-tRNA Ligase / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D004274:DNA, Recombinant; D014364:Tryptophan; D000604:Amino Acyl-tRNA Synthetases; D014369:Tryptophan-tRNA Ligase