CRP INDUCES THE REPOSITIONING OF MALT AT THE ESCHERICHIA-COLI MALKP PROMOTER PRIMARILY THROUGH DNA BENDING

Activation of transcription initiation at the Escherichia coli malKp promoter requires the repositioning of MalT, the primary activator, from a set of non-productive sites to a set of productive sites, which is staggered by 3 bp. Occupation of the latter relies on the formation of a higher order structure involving distal MalT sites and the binding of CRP (cAMP receptor protein) to three sites located in the intervening region. We show here that one can successfully replace all of the CRP sites by the binding site of another DNA-bending protein, integration host factor, or by a sequence-directed bend without altering the process of malKp activation. This observation indicates that CRP action at malKp does not involve critical interactions with MalT and that CRP promotes MalT repositioning primarily through DNA bending. This structural role of CRP differs markedly from its role in the activation of the lac promoter.