Characterization of Mycobacterium tuberculosis RV3676 (CRPMT), a cyclic AMP receptor protein-like DNA binding protein

Little is known about cyclic AMP (cAMP) function in Mycobacterium tuberculosis, despite its ability to encode 15 adenylate cyclases and 10 cNMP-binding proteins. M. tuberculosis Rv3676, which we have designated CRPMt, is predicted to be a cAMP-dependent transcription factor. In this study, we characterized CRPMt's interactions with DNA and cAMP, using experimental and computational approaches. We used Gibbs sampling to define a CRPMt DNA motif that resembles the cAMP receptor protein (CRP) binding motif model for Escherichia coli. CRPMt binding sites were identified in a total of 73 promoter regions regulating 114 genes in the M. tuberculosis genome, which are being explored as a regulon. Specific CRPMt binding caused DNA bending, and the substitution of highly conserved nucleotides in the binding site resulted in a complete loss of binding to CRPMt. cAMP enhanced CRPMt's ability to bind DNA and caused allosteric alterations in CRP,, conformation. These results provide the first direct evidence for cAMP binding to a transcription factor in M. tuberculosis, suggesting a role for cAMP signal transduction in M. tuberculosis and implicating CRPMt as a cAMP-responsive global regulator.