Crystal structure of a Streptococcal protein G B1 mutant

Experimental Data Snapshot

  • Resolution: 1.40 Å
  • R-Value Free: 0.224 
  • R-Value Work: 0.176 
  • R-Value Observed: 0.179 

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Optimizing pH response of affinity between protein G and IgG Fc: how electrostatic modulations affect protein-protein interactions.

Watanabe, H.Matsumaru, H.Ooishi, A.Feng, Y.Odahara, T.Suto, K.Honda, S.

(2009) J Biol Chem 284: 12373-12383

  • DOI: https://doi.org/10.1074/jbc.M809236200
  • Primary Citation of Related Structures:  
    2ZW0, 2ZW1

  • PubMed Abstract: 

    Protein-protein interaction in response to environmental conditions enables sophisticated biological and biotechnological processes. Aiming toward the rational design of a pH-sensitive protein-protein interaction, we engineered pH-sensitive mutants of streptococcal protein G B1, a binder to the IgG constant region. We systematically introduced histidine residues into the binding interface to cause electrostatic repulsion on the basis of a rigid body model. Exquisite pH sensitivity of this interaction was confirmed by surface plasmon resonance and affinity chromatography employing a clinically used human IgG. The pH-sensitive mechanism of the interaction was analyzed and evaluated from kinetic, thermodynamic, and structural viewpoints. Histidine-mediated electrostatic repulsion resulted in significant loss of exothermic heat of the binding that decreased the affinity only at acidic conditions, thereby improving the pH sensitivity. The reduced binding energy was partly recovered by "enthalpy-entropy compensation." Crystal structures of the designed mutants confirmed the validity of the rigid body model on which the effective electrostatic repulsion was based. Moreover, our data suggested that the entropy gain involved exclusion of water molecules solvated in a space formed by the introduced histidine and adjacent tryptophan residue. Our findings concerning the mechanism of histidine-introduced interactions will provide a guideline for the rational design of pH-sensitive protein-protein recognition.

  • Organizational Affiliation

    National Institute of Advanced Industrial Science and Technology, Central 6, Tsukuba 305-8566, Japan.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Protein LG57Finegoldia magnaMutation(s): 4 
Find proteins for Q53291 (Finegoldia magna)
Explore Q53291 
Go to UniProtKB:  Q53291
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ53291
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.40 Å
  • R-Value Free: 0.224 
  • R-Value Work: 0.176 
  • R-Value Observed: 0.179 
  • Space Group: C 2 2 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 25.764α = 90
b = 36.36β = 90
c = 93.688γ = 90
Software Package:
Software NamePurpose
HKL-2000data collection
HKL-2000data reduction
HKL-2000data scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2009-03-03
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Version format compliance
  • Version 1.2: 2014-03-05
    Changes: Database references
  • Version 1.3: 2021-11-10
    Changes: Database references, Derived calculations