title: Roles of the GcvA and PurR proteins in negative regulation of the Escherichia coli glycine cleavage enzyme system.
abstract: When Escherichia coli was grown in medium containing both inosine and glycine, the PurR repressor protein was shown to be responsible for a twofold reduction from the fully induced glycine cleavage enzyme levels. This twofold repression was also seen by measuring beta-galactosidase levels in cells carrying a lambda gcvT-lacZ gene fusion. In this fusion, the synthesis of beta-galactosidase is under the control of the gcv regulatory region. A DNA fragment carrying the gcv control region was shown by gel mobility shift assay and DNase I footprinting to bind purified PurR protein, suggesting a direct involvement of the repressor in gcv regulation. A separate mechanism of purine-mediated regulation of gcv was shown to be independent of the purR gene product and resulted in an approximately 10-fold reduction of beta-galactosidase levels when cells were grown in medium containing inosine but lacking the inducer glycine. This additional repression was dependent upon a functional gcvA gene, a positive activator for the glycine cleavage enzyme system. A dual role for the GcvA protein as both an activator in the presence of glycine and a repressor in the presence of inosine is suggested.
authors.affiliation: Department of Microbiology, University of Iowa, Iowa City 52242.
authors.forename: R L
authors.initials: RL
authors.lastname: Wilson
authors.forename: L T
authors.initials: LT
authors.lastname: Stauffer
authors.forename: G V
authors.initials: GV
authors.lastname: Stauffer
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004794:Enzyme Repression; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics*; D009154:Mutation; D011687:Purines / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D014166:Transferases / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D009097:Multienzyme Complexes; C065825:PurR protein, Bacteria; C489317:PurR protein, E coli; D011687:Purines; D012097:Repressor Proteins; C064525:glycine cleavage system; D000594:Amino Acid Oxidoreductases; D014166:Transferases