title: Spacing and orientation requirements of GcvA-binding sites 3 and 2 and the Lrp-binding region for gcvT::lacZ expression in Escherichia coli.
abstract: Both GcvA and Lrp are required for normal regulation of the gcv operon. Moving the GcvA-binding sites 3 and 2 and the Lrp-binding region either closer to, or further away from, the gcv promoter by approximately one helical turn of DNA resulted in a less than twofold decrease in glycine-mediated activation or inosine-mediated repression of a gcvT::IacZ fusion. Moving these sites approximately two helical turns of DNA away from the gcv promoter resulted in a further loss of both activation and repression; moving these sites approximately three helical turns of DNA from the gcv promoter resulted in an essentially complete loss of both glycine-mediated activation and inosine-mediated repression. However, when these sites were moved by approximately 1.5 and 2.5 helical turns of DNA away from the gcv promoter, there was a complete loss of both glycine-mediated activation and inosine-mediated repression of the gcvT::IacZ fusion. The flexibility in the absolute distance of the GcvA- and Lrp-binding sites relative to the gcv promoter, but strict orientation dependence of these sites is consistent with a possible protein-protein interaction of either GcvA, Lrp, or both of these proteins with RNA polymerase. Because of the location of these target sites relative to the gcv promoter, it is also likely that DNA looping is required for this mechanism of regulation.
authors.affiliation: Department of Microbiology, University of Iowa, Iowa City, IA 52242, USA.
authors.forename: Lorraine T
authors.initials: LT
authors.lastname: Stauffer
authors.affiliation: Department of Microbiology, University of Iowa, Iowa City, IA 52242, USA.
authors.forename: George V
authors.initials: GV
authors.lastname: Stauffer
mesh_terms: D050960:Aminomethyltransferase; D010582:Bacteriophage lambda / Q000235:genetics; D001483:Base Sequence; D001665:Binding Sites; D004269:DNA, Bacterial; 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; D019077:Helix-Turn-Helix Motifs; D019877:Hydroxymethyl and Formyl Transferases / Q000235:genetics*; D007288:Inosine / Q000378:metabolism; D007763:Lac Operon; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D008969:Molecular Sequence Data; D009876:Operon; D011401:Promoter Regions, Genetic; D011971:Receptors, Immunologic / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C095454:GcvA protein, E coli; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D011971:Receptors, Immunologic; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D007288:Inosine; D019877:Hydroxymethyl and Formyl Transferases; D050960:Aminomethyltransferase; D001616:beta-Galactosidase; D005998:Glycine