Structural basis for cAMP-mediated allosteric control of the catabolite activator protein.
The cAMP-mediated allosteric transition in the catabolite activator protein (CAP; also known as the cAMP receptor protein, CRP) is a textbook example of modulation of DNA-binding activity by small-molecule binding. Here we report the structure of CAP in the absence of cAMP, which, together with structures of CAP in the presence of cAMP, defines atomic details of the cAMP-mediated allosteric transition. The structural changes, and their relationship to cAMP binding and DNA binding, are remarkably clear and simple. Binding of cAMP results in a coil-to-helix transition that extends the coiled-coil dimerization interface of CAP by 3 turns of helix and concomitantly causes rotation, by approximately 60 degrees , and translation, by approximately 7 A, of the DNA-binding domains (DBDs) of CAP, positioning the recognition helices in the DBDs in the correct orientation to interact with DNA. The allosteric transition is stabilized further by expulsion of an aromatic residue from the cAMP-binding pocket upon cAMP binding. The results define the structural mechanisms that underlie allosteric control of this prototypic transcriptional regulatory factor and provide an illustrative example of how effector-mediated structural changes can control the activity of regulatory proteins.
Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08854, USA.
Nataliya
N
Popovych
Shiou-Ru
SR
Tzeng
Marco
M
Tonelli
Richard H
RH
Ebright
Charalampos G
CG
Kalodimos
D000494:Allosteric Regulation; D001059:Apoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000242:Cyclic AMP / Q000737:chemistry / Q000378:metabolism; D002373:Cyclic AMP Receptor Protein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006152:Cyclic GMP / Q000737:chemistry / Q000378:metabolism; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D010641:Phenotype; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary
D001059:Apoproteins; D002373:Cyclic AMP Receptor Protein; D004247:DNA; D000242:Cyclic AMP; D006152:Cyclic GMP