FIG 3.

Current understanding of erp regulatory circuits. Each cp32 produces a distinct BpaB. However, all cp32-encoded BpaB proteins contain a conserved amino acid motif that binds to erp operator DNA. That feature permits cross talk and coordinated repression/derepression of all erp operons in a bacterium. BpuR can bind its own mRNA and inhibit translation. DnaA binds to bpuR promoter DNA between the −10 and −35 sequences. EbfC is cotranscribed with dnaX, which encodes the tau subunit of DNA polymerase III. Both DnaA and EbfC bind to sequences between the dnaX-ebfC promoter and the initiation codon of dnaX. EbfC also binds to the 5′ untranslated region of the dnaX-ebfC mRNA. DnaA binds to its own 5′ DNA. Promoter −35 and −10 elements are indicated by solid black bars 5′ of the ORFs. The illustrated structures of BpuR and EbfC are adapted from the solved and modeled proteins (123, 128, 131).