| Summary: | <p>Abstract</p> <p>Background</p> <p>The cAMP receptor protein (CRP) is a global bacterial regulator that controls many target genes. The CRP-cAMP complex regulates the <it>ompR-envZ </it>operon in <it>E. coli </it>directly, involving both positive and negative regulations of multiple target promoters; further, it controls the production of porins indirectly through its direct action on <it>ompR-envZ</it>. Auto-regulation of CRP has also been established in <it>E. coli</it>. However, the regulation of porin genes and its own gene by CRP remains unclear in <it>Y. pestis</it>.</p> <p>Results</p> <p><it>Y. pestis </it>employs a distinct mechanism indicating that CRP has no regulatory effect on the <it>ompR-envZ </it>operon; however, it stimulates <it>ompC </it>and <it>ompF </it>directly, while repressing <it>ompX</it>. No transcriptional regulatory association between CRP and its own gene can be detected in <it>Y. pestis</it>, which is also in contrast to the fact that CRP acts as both repressor and activator for its own gene in <it>E. coli</it>. It is likely that <it>Y. pestis </it>OmpR and CRP respectively sense different signals (medium osmolarity, and cellular cAMP levels) to regulate porin genes independently.</p> <p>Conclusion</p> <p>Although the CRP of <it>Y. pestis </it>shows a very high homology to that of <it>E. coli</it>, and the consensus DNA sequence recognized by CRP is shared by the two bacteria, the <it>Y. pestis </it>CRP can recognize the promoters of <it>ompC</it>, <it>F</it>, and <it>X </it>directly rather than that of its own gene, which is different from the relevant regulatory circuit of <it>E. coli</it>. Data presented here indicate a remarkable remodeling of the CRP-mediated regulation of porin genes and of its own one between these two bacteria.</p>
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