Profound asymmetry in the structure of the cAMP-free cAMP Receptor Protein (CRP) from Mycobacterium tuberculosis.

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TitleProfound asymmetry in the structure of the cAMP-free cAMP Receptor Protein (CRP) from Mycobacterium tuberculosis.
Publication TypeJournal Article
Year of Publication2009
AuthorsD Gallagher, T, Smith, N, Kim, S-K, Robinson, H, Reddy, PT
JournalJ Biol Chem
Volume284
Issue13
Pagination8228-32
Date Published2009 Mar 27
ISSN0021-9258
KeywordsAllosteric Regulation, Bacterial Proteins, Crystallography, X-Ray, Cyclic AMP, Cyclic AMP Receptor Protein, DNA, Bacterial, Escherichia coli, Escherichia coli Proteins, Mycobacterium tuberculosis, Protein Structure, Tertiary
Abstract

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 H(37)R(v) (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 Calpha 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.

DOI10.1074/jbc.C800215200
Alternate JournalJ. Biol. Chem.
PubMed ID19193643
PubMed Central IDPMC2659179
Grant ListP30 EB009998 / EB / NIBIB NIH HHS / United States