Abstract
OmpR, the transcriptional regulatory protein of ompF, had not been previously shown to specifically bind to the −70 to −60-bp region of ompF. We show that the −102 to −76-bp sequence of ompF has a high affinity binding site for OmpR and produced a single OmpR/ ompF complex (complex b). Extension of this DNA fragment to include an inverted repeat sequence located between the −71 and −64-bp region resulted in the formation of a second, slower migrating complex (complex a). A −102 to −58-bp fragment containing a substitution of the −70 CG bp was able to form complex b, but not complex a. A mutant OmpR protein derived from a strain that can not repress ompF was unable to form complex a, while complex b was formed normally. Deletion of the −70 CG bp resulted in incomplete repression of OmpF. These results suggest that OmpR binds to the −71 to −64-bp region and that this sequence plays a role in the regulation of ompF in Escherichia coli.
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