Converting Escherichia coli RNA Polymerase into an Enhancer-Responsive Enzyme: Role of an NH2-Terminal Leucine Patch in σ54

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Science  10 Nov 1995:
Vol. 270, Issue 5238, pp. 992-994
DOI: 10.1126/science.270.5238.992


The protein σ54 associates with Escherichia coli core RNA polymerase to form a holoenzyme that binds promoters but is inactive in the absence of enhancer activation. Here, mutants of σ54 enabled polymerases to transcribe without enhancer protein and adenosine triphosphate. The mutations are in leucines within the NH2-terminal glutamine-rich domain of σ54. Multiple leucine substitutions mimicked the effect of enhancer protein, which suggests that the enhancer protein functions to disrupt a leucine patch. The results indicate that σ54 acts both as an inhibitor of polymerase activity and as a receptor that interacts with enhancer protein to overcome this inhibition, and that these two activities jointly confer enhancer responsiveness.

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