title: Two control systems modulate the level of glutaminyl-tRNA synthetase in Escherichia coli.
abstract: We studied the regulation of in vivo expression of Escherichia coli glutaminyl-tRNA synthetase at the transcriptional and translational level by analysis of glnS mRNA and glutaminyl-tRNA synthetase levels under a variety of growth conditions. In addition, strains carrying fusions of the beta-galactosidase structural gene and the glnS promoter were constructed and subsequently used for glnS regulatory studies. The level of glutaminyl-tRNA synthetase increases with the increasing growth rate, with a concomitant though much larger increase in glnS mRNA levels. Thus, transcriptional control appears to mediate metabolic regulation. It is known that glnR5, a regulatory mutation unlinked to glnS, causes overproduction of glutaminyl-tRNA synthetase. Here we showed that the glnR5 product enhances transcription of glnS 10- to 15-fold. The glnR5 mutation does not affect metabolic control. Thus, glnS appears to be regulated by two different control systems affecting transcription. Furthermore, our results suggest post-transcriptional regulation of glutaminyl-tRNA synthetase.
authors.forename: A Y
authors.initials: AY
authors.lastname: Cheung
authors.forename: L
authors.initials: L
authors.lastname: Watson
authors.forename: D
authors.initials: D
authors.lastname: Söll
mesh_terms: D000604:Amino Acyl-tRNA Synthetases / Q000235:genetics*; D002455:Cell Division; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D005975:Glutamate-tRNA Ligase / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D009693:Nucleic Acid Hybridization; D011401:Promoter Regions, Genetic; D012329:RNA, Bacterial / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000235:genetics
chemical_list: D012329:RNA, Bacterial; D012333:RNA, Messenger; D001616:beta-Galactosidase; D000604:Amino Acyl-tRNA Synthetases; D005975:Glutamate-tRNA Ligase