1AB7

NMR 15N RELAXATION AND STRUCTURAL STUDIES REVEAL CONFORMATIONAL EXCHANGE IN BARSTAR C40/82A, 30 STRUCTURES


Experimental Data Snapshot

  • Method: SOLUTION NMR
  • Conformers Calculated: 150 
  • Conformers Submitted: 30 
  • Selection Criteria: LEAST RESTRAINT VIOLATION 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

NMR 15N relaxation and structural studies reveal slow conformational exchange in barstar C40/82A.

Wong, K.B.Fersht, A.R.Freund, S.M.

(1997) J.Mol.Biol. 268: 494-511

  • DOI: 10.1006/jmbi.1997.0989

  • PubMed Abstract: 
  • Barstar an 89-residue protein consisting of four helices and a three-stranded parallel beta-sheet, is the intracellular inhibitor of the endoribonuclease barnase. Barstar C40/82A, a mutant in which the two cysteine residues have been replaced by alan ...

    Barstar an 89-residue protein consisting of four helices and a three-stranded parallel beta-sheet, is the intracellular inhibitor of the endoribonuclease barnase. Barstar C40/82A, a mutant in which the two cysteine residues have been replaced by alanine, has been used as a pseudo wild-type in folding studies and in the crystal structure of the barnase:barstar C40/82A complex. We have determined a high resolution solution structure of barstar C40/82A. The structures of barstar C40/82A and the wild-type are superimposable. A comparison with the crystal structure of the barnase:barstar C40/82A complex revealed subtle differences in the regions involved in the binding of barstar to barnase. Side-chain rotations of residues Asn33, Asp35 and Asp39 and a movement of the binding loop (Pro27-Glu32) towards the binding site of barnase facilitate the formation of interface hydrogen bonds and aromatic contacts in the complex. Extreme line broadening and missing signals in 1H-15N correlation spectra indicate substantial conformational exchange for a large subset of residues. 15N relaxation data at two magnetic field strengths, 11.74 T and 14.10 T, were used to estimate exchange contributions and to map the spectral density function at five frequencies: 0, 50, 60, 450 and 540 MHz. Based on these results, model-free calculations with the inclusion of estimated exchange contributions were used to derive order parameters and internal correlation times. The validity of this approach has been investigated with model-free calculations that incorporate longitudinal relaxation rates and heteronuclear 1H-15N NOE data only at 11.74 T and 14.10 T. The relaxation data suggest substantial conformational exchange in regions of barstar C40/82A, including the binding loop, the second and the third helices, and the second and the third strands. Amide proton exchange experiments suggest a stable hydrogen bond network for all helices and sheets except the third helix and the C-terminal of the second and the third strands. The combined results indicate a rigid body movement of the second helix and twisting motions of the beta-sheet of barstar, which might be important for the interaction with barnase.


    Related Citations: 
    • Barnase and Barstar: Two Small Proteins to Fold and Fit Together
      Hartley, R.W.
      (1989) Trends Biochem.Sci. 14: 450


    Organizational Affiliation

    MRC Unit for Protein Function and Design, Cambridge Centre for Protein Engineering, University Chemical Laboratory, UK.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
BARSTAR
A
89Bacillus amyloliquefaciensMutation(s): 2 
Find proteins for P11540 (Bacillus amyloliquefaciens)
Go to UniProtKB:  P11540
Experimental Data & Validation

Experimental Data

  • Method: SOLUTION NMR
  • Conformers Calculated: 150 
  • Conformers Submitted: 30 
  • Selection Criteria: LEAST RESTRAINT VIOLATION 
  • Olderado: 1AB7 Olderado
Software Package:
Software NamePurpose
X-PLORphasing
X-PLORrefinement
X-PLORmodel building

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 1997-09-04
    Type: Initial release
  • Version 1.1: 2008-03-24
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance