RNA polymerase and gal repressor bind simultaneously and with DNA bending to the control region of the Escherichia coli galactose operon.

摘要: The Escherichia coli galactose operon contains an unusual array of closely spaced binding sites for proteins governing the expression from two physically overlapping gal promoters. Based on studies promoter-up mutants we have previously suggested RNA-polymerase-induced DNA bending promoter DNA. Here present new evidence confirming and extending this interpretation. It was obtained by circular permutation assay gel electrophoretic mobility [Wu Crothers (1984), Nature, 308, 509-513] applied to three analogous series circularly permuted fragments derived wild-type mutant DNAs. same further been used study repressor its operator shift DNase I footprinting techniques. main results are: (i) complexes carrying either exclusively at upstream O1 or downstream O2 exhibit different mobilities; (ii) one operators in protein-induced criteria assay; (iii) occupation both does not prevent cAMP-CRP-independent RNA polymerase promoters, as judged protection retardation assays. latter finding imposes constraints any attempt model regulation assumed DNA-protein protein-protein interactions.