title: Maintenance of repression control of the ilvGMEDA operon in a temperature-sensitive leucyl-transfer RNA synthetase mutant of Escherichia coli K-12 at a restrictive temperature.
abstract: The mechanism of L-leucine regulation of ilvGMEDA is thought to be by ribosome-mediated attenuation that is dependent upon the concentration of Leu-tRNA(Leu) which results from leucyl-tRNA synthetase (LeuRS) activity. The requirement for LeuRS activity in attenuation control was tested in an Escherichia coli K-12 strain containing a temperature-sensitive LeuRS and the ilvGMEDA operon with an active ilvGM. Growth of this strain at 30 degrees C followed by a shift to 37 degrees C to inactivate the LeuRS revealed that ilvGM expression decreased at the restrictive temperature whereas the downstream gene expression was slightly elevated. We suggest that ilvGM does not respond to a deattenuation signal, and that, possibly, a secondary repression/derepression mechanism exists.
authors.affiliation: Department of Biology, North Carolina A & T State University, Greensboro 27411.
authors.forename: J J
authors.initials: JJ
authors.lastname: Whittaker
authors.forename: J H
authors.initials: JH
authors.lastname: Jackson
mesh_terms: D000595:Amino Acid Sequence; D003062:Codon; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D007930:Leucine / Q000235:genetics / Q000494:pharmacology; D007935:Leucine-tRNA Ligase / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D009876:Operon; D021382:Protein Sorting Signals / Q000737:chemistry / Q000235:genetics; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism; D013696:Temperature
chemical_list: D003062:Codon; D021382:Protein Sorting Signals; D012346:RNA, Transfer, Amino Acyl; D007935:Leucine-tRNA Ligase; D007930:Leucine