title: Glycine binds the transcriptional accessory protein GcvR to disrupt a GcvA/GcvR interaction and allow GcvA-mediated activation of the Escherichia coli gcvTHP operon.
abstract: The Escherichia coli gcvTHP operon is under control of the LysR-type transcriptional regulator GcvA. GcvA activates the operon in the presence of glycine and represses the operon in its absence. Repression by GcvA is dependent on a second regulatory protein, GcvR. Generally, LysR-type transcriptional regulators bind to specific small co-effector molecules which results in either their altered affinity for specific binding sites on the DNA or altered ability to bend the DNA, resulting in either activation or repression of their respective operons. This study shows that glycine, the co-activator for the gcv operon, does not alter either GcvA's ability to bind DNA nor its ability to bend DNA. Rather, glycine binds to GcvR, disrupting a GcvA/GcvR interaction required for repression and allowing GcvA activation of the gcvTHP operon. Amino acid changes in GcvR that reduce glycine binding result in a loss of glycine-mediated activation in vivo.
authors.affiliation: Department of Microbiology, The University of Iowa, Iowa City, IA 52242, USA1.
authors.forename: Gary
authors.initials: G
authors.lastname: Heil
authors.affiliation: Department of Microbiology, The University of Iowa, Iowa City, IA 52242, USA1.
authors.forename: Lorraine T
authors.initials: LT
authors.lastname: Stauffer
authors.affiliation: Department of Microbiology, The University of Iowa, Iowa City, IA 52242, USA1.
authors.forename: George V
authors.initials: GV
authors.lastname: Stauffer
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D005998:Glycine / Q000378:metabolism*; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism*; D009876:Operon; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014166:Transferases / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C095454:GcvA protein, E coli; C095455:GcvR protein, E coli; D009097:Multienzyme Complexes; D012097:Repressor Proteins; D014157:Transcription Factors; C064525:glycine cleavage system; D000594:Amino Acid Oxidoreductases; D014166:Transferases; D005998:Glycine