Figure 5.

Model for the regulation of ompF by OmpR-P. According to this model, the unphosphorylated form of OmpR binds primarily to the F1 site. (A) Although occupancy of the F2 site may occur in the absence of OmpR phosphorylation, this occupancy does not seem to be sufficient to activate ompF transcription. (B) In contrast, phosphorylation of OmpR results in increased occupancy of the F2 site due to the stimulation of cooperative interactions. We proposed that the increased occupancy of the F2 site is responsible for the observed activation of ompF transcription under low osmolarity conditions.