Experimental Data Snapshot

  • Resolution: 1.82 Å
  • R-Value Free: 0.300 
  • R-Value Work: 0.227 
  • R-Value Observed: 0.228 

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The structure of the T127L/S128A mutant of cAMP receptor protein facilitates promoter site binding

Chu, S.Y.Tordova, M.Gilliland, G.L.Gorshkova, I.Shi, Y.Wang, S.Schwarz, F.P.

(2001) J Biol Chem 276: 11230-11236

  • DOI: https://doi.org/10.1074/jbc.M010428200
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    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*.

  • Organizational Affiliation

    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.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
A, B
210Escherichia coliMutation(s): 2 
Gene Names: CRP/CAP
Find proteins for P0ACJ8 (Escherichia coli (strain K12))
Explore P0ACJ8 
Go to UniProtKB:  P0ACJ8
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP0ACJ8
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.82 Å
  • R-Value Free: 0.300 
  • R-Value Work: 0.227 
  • R-Value Observed: 0.228 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 46.1α = 90
b = 93.1β = 90
c = 104.4γ = 90
Software Package:
Software NamePurpose
X-GENdata scaling
X-GENdata reduction

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2001-01-17
    Type: Initial release
  • Version 1.1: 2008-04-27
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2017-10-04
    Changes: Refinement description
  • Version 1.4: 2021-10-27
    Changes: Database references, Derived calculations
  • Version 1.5: 2023-08-09
    Changes: Data collection, Refinement description