FIGURE 6.

A proposed role for CpxR-dependent regulation in E. coli resistance to CAMP. The CpxR/CpxA response induces the expression of a variety of genes encoding MarA, MarR, AroK, and other envelope folding factors DsbA, DegP, etc. CpxR-induced MarA activates the genes encoding TolC and other components of tripartite multidrug transporters. DegP and DsbA affect assembly of these transporters, which mediate efflux of the CAMPs into the cytoplasm. AroK mediates production of indole, which is exported and stimulates the CpxR/CpxA system, resulting in activation of mar transcription. In the meantime, AroK also mediates production of salicylate and 2,3-dihydroxybenzoate, which bind to MarR to derepress mar transcription. OM and IM are bacterial outer and inner membranes, respectively.