Structural Insights into the Mechanism of the Allosteric Transitions of Mycobacterium tuberculosis cAMP Receptor Protein*

By M. Reddy, S. Palaninathan, J. Bruning, C. Thurman, Danielle G. Smith, J. Sacchettini. 2009

39 citations recorded by the source corpus.

The cAMP receptor protein (CRP) from Mycobacterium tuberculosis is a cAMP-responsive global transcriptional regulator, responsible for the regulation of a multitude of diverse proteins. We have determined the crystal structures of the CRP·cAMP and CRP·N6-cAMP derivative-bound forms of the enzyme to 2.2- and 2.3 Å-resolution, respectively, to investigate cAMP-mediated conformational and structural changes. The allosteric switch from the open, inactive conformation to the closed, active conformation begins with a number of changes in the ligand-binding cavity upon cAMP binding. These subtle structural changes and numerous non-bonding interactions between cAMP, the N-domain residues, and the C-domain helices demonstrate that the N-domain hairpin loop acts as a structural mediator of the allosteric switch. Based on the CRP·N6-cAMP crystal structure, binding of N6-cAMP with a bulkier methylphenylethyl extension from the N6 atom stabilizes the cAMP-binding domain, N-domain hairpin, and C-terminal domain in a similar manner as that of the CRP·cAMP structure, maintaining structural integrity within the subunits. However, the bulkier N6 extension of N6-cAMP (in R conformation) is accommodated only in subunit A with minor changes, whereas in subunit B, the N6 extension is in the S conformation hindering the hinge region of the central helix. As a result, the entire N-domain and the C-domain of subunit B integrated by the cAMP portion of this ligand, together tilt away (∼7° tilt) from central helix C, positioning the helix-turn-helix motif in an unfavorable position for the DNA substrate, asymmetrically. Together, these crystal structures demonstrate the mechanism of action of the cAMP molecule and its role in integrating the active CRP structure.

Subfields: Infectious Diseases, Materials Chemistry, Molecular Biology

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Citations in the corpus

• Structural Basis of Dual Specificity of Sinorhizobium meliloti Clr, a cAMP and cGMP Receptor Protein (2023, background): “culosis Rv3676 and has been assumed to be a generic trait of CRP-like proteins (43).”
• Structures of inactive CRP species reveal the atomic details of the allosteric transition that discriminates cyclic nucleotide second messengers. (2014, background): “However, this indirect interaction does not appear to be a critical factor for selecting the anti conformation of cAMP because it was not evident in the cAMP-bound complex of the CRP orthologue from M. tuberculosis (Reddy et al., 2009).”
• Cyclic AMP Signaling in Mycobacteria (2014, background): “While it is likely that a cAMP-induced repositioning of CRPMt’s helix-turn-helix domain affects its DNA binding properties, questions remain about the extent of this helix reorientation, the amount of asymmetry between subunits, and the effects of this asymmetry (54, 76, 77).”
• Directed Evolution of the Escherichia coli cAMP Receptor Protein at the cAMP Pocket* (2015, background): “Several of these CRP proteins have been crystallized, in which the dyads are visualized to interact with cAMP through hydrogen bonding interactions (7, 28, 30, 37).”
• Genomic mapping of cAMP receptor protein (CRPMt) in Mycobacterium tuberculosis: relation to transcriptional start sites and the role of CRPMt as a transcription factor (2014, background): “Whilst some structural studies demonstrate a conformational change associated with binding of cAMP (55), biochemical analysis shows that this has little or no effect on binding to DNA (21).”