Regulation of open complex formation at the Escherichia coli galactose operon promoters. Simultaneous interaction of RNA polymerase, gal repressor and CAP/cAMP.

摘要: The regulation of open complex formation at the Escherichia coli galactose operon promoters by repressor and catabolite activator protein/cyclic AMP (CAP/cAMP) was investigated in DNA-binding kinetic experiments performed vitro. We found that gal CAP/cAMP bind to regulatory region independently, resulting simultaneous occupancy two operators binding site. Both altered partitioning RNA polymerase between overlapping promoters. Open complexes formed absence added proteins were partitioned P1 P2 with occupancies 25% 75%, respectively. caused be nearly exclusively (98% occupancy), a co-ordinated, but incomplete, switch promoter from both presence . measured constants governing decay CAP/cAMP. had largest effect on kinetics formation, 30-fold increase apparent constant. conclude does not result competition repressor, for region, instead results interactions three during nucleoprotein DNA fragment. Finally, we present model operon.