Profound Asymmetry in the Structure of the cAMP-free cAMP Receptor Protein (CRP) from Mycobacterium tuberculosis
The cyclic AMP receptor protein (CRP, also called catabolite gene activator protein or CAP) plays a key role in metabolic regulation in bacteria and has become a widely studied model allosteric transcription factor. On binding its effector cAMP in the N-terminal domain, CRP undergoes a structural transition to a conformation capable of specific DNA binding in the C-terminal domain and transcription initiation. The crystal structures of Escherichia coli CRP (EcCRP) in the cAMP-bound state, both with and without DNA, are known, although its structure in the off state (cAMP-free, apoCRP) remains unknown. We describe the crystal structure at 2.0A resolution of the cAMP-free CRP homodimer from Mycobacterium tuberculosis H37Rv (MtbCRP), whose sequence is 30% identical with EcCRP, as the first reported structure of an off-state CRP. The overall structure is similar to that seen for the cAMP-bound EcCRP, but the apo MtbCRP homodimer displays a unique level of asymmetry, with a root mean square deviation of 3.5A between all C? positions in the two subunits. Unlike structures of on-state EcCRP and other homologs in which the C-domains are asymmetrically positioned but possess the same internal conformation, the two C-domains of apo MtbCRP differ both in hinge structure and in internal arrangement, with numerous residues that have completely different local environments and hydrogen bond interactions, especially in the hinge and DNA-binding regions. Comparison of the structures of apo MtbCRP and DNA-bound EcCRP shows how DNA binding would be inhibited in the absence of cAMP and supports a mechanism involving functional asymmetry in apoCRP.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 980409
- Report Number(s):
- BNL-93327-2010-JA; JBCHA3; TRN: US201015%%1794
- Journal Information:
- Journal of Biological Chemistry, Vol. 284; ISSN 0021-9258
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
AMP
ASYMMETRY
BACTERIA
CRYSTAL STRUCTURE
DNA
ESCHERICHIA COLI
FUNCTIONALS
GENE REGULATION
HYDROGEN
INTERACTIONS
MYCOBACTERIUM TUBERCULOSIS
PROTEINS
RECEPTORS
REGULATIONS
RESIDUES
RESOLUTION
ROOTS
SUPPORTS
TRANSCRIPTION
TRANSCRIPTION FACTORS
national synchrotron light source