The structure of the T127L/S128A mutant of cAMP receptor protein facilitates promoter site bindingChu, S.Y., Tordova, M., Gilliland, G.L., Gorshkova, I., Shi, Y., Wang, S., Schwarz, F.P.
(2001) J.Biol.Chem. 276: 11230-11236
- PubMed: 11124966
- DOI: 10.1074/jbc.M010428200
- PubMed Abstract:
- Structure of a Complex of Catabolite Gene Activator Protein and Cyclic AMP Refined at 2.5 A Resolution
Weber, I.T.,Steitz, T.A.
(1987) J.Mol.Biol. 198: 311
- Crystal Structure of a Cyclic AMP-independent Mutant of Catabolite Gene Activator Protein
Weber, I.T.,Gilliland, G.L.,Harman, J.G.,Peterkofsky, A.
(1987) J.Biol.Chem. 262: 5630
- The Structure of a CAP-DNA Complex Having Two cAMP Molecules Bound To Each Monomer
Passner, J.M.,Steitz, T.A.
(1997) Proc.Natl.Acad.Sci.USA 94: 2843
The x-ray crystal structure of the cAMP-ligated T127L/S128A double mutant of cAMP receptor protein (CRP) was determined to a resolution of 2.2 A. Although this structure is close to that of the x-ray crystal structure of cAMP-ligated CRP with one sub ...
The x-ray crystal structure of the cAMP-ligated T127L/S128A double mutant of cAMP receptor protein (CRP) was determined to a resolution of 2.2 A. Although this structure is close to that of the x-ray crystal structure of cAMP-ligated CRP with one subunit in the open form and one subunit in the closed form, a bound syn-cAMP is clearly observed in the closed subunit in a third binding site in the C-terminal domain. In addition, water-mediated interactions replace the hydrogen bonding interactions between the N(6) of anti-cAMP bound in the N-terminal domains of each subunit and the OH groups of the Thr(127) and Ser(128) residues in the C alpha-helix of wild type CRP. This replacement induces flexibility in the C alpha-helix at Ala(128), which swings the C-terminal domain of the open subunit more toward the N-terminal domain in the T127L/S128A double mutant of CRP (CRP*) than is observed in the open subunit of cAMP-ligated CRP. Isothermal titration calorimetry measurements on the binding of cAMP to CRP* show that the binding mechanism changes from an exothermic independent two-site binding mechanism at pH 7.0 to an endothermic interacting two-site mechanism at pH 5.2, similar to that observed for CRP at both pH levels. Differential scanning calorimetry measurements exhibit a broadening of the thermal denaturation transition of CRP* relative to that of CRP at pH 7.0 but similar to the multipeak transitions observed for cAMP-ligated CRP. These properties and the bound syn-cAMP ligand, which has only been previously observed in the DNA bound x-ray crystal structure of cAMP-ligated CRP by Passner and Steitz (Passner, J. M., and Steitz, T. A. (1997) Proc. Natl. Acad. Sci. U. S. A. 94, 2843-2847), imply that the cAMP-ligated CRP* structure is closer to the conformation of the allosterically activated structure than cAMP-ligated CRP. This may be induced by the unique flexibility at Ala(128) and/or by the bound syn-cAMP in the hinge region of CRP*.
Center for Advanced Research in Biotechnology of the National Institute of Standards and Technology and the University of Maryland Biotechnology Institute, Rockville, Maryland 20850, USA.