Experimental Data Snapshot

  • Resolution: 2.00 Å
  • R-Value Free: 0.287 
  • R-Value Work: 0.209 
  • R-Value Observed: 0.217 

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The role of Asn14 in the stability and conformation of the reactive-site loop of winged bean chymotrypsin inhibitor: crystal structures of two point mutants Asn14-->Lys and Asn14-->Asp.

Ravichandran, S.Dasgupta, J.Chakrabarti, C.Ghosh, S.Singh, M.Dattagupta, J.K.

(2001) Protein Eng 14: 349-357

  • DOI: https://doi.org/10.1093/protein/14.5.349
  • Primary Citation of Related Structures:  
    1EYL, 1FMZ, 1FN0

  • PubMed Abstract: 

    A double-headed chymotrypsin inhibitor, WCI, from winged bean seeds was cloned for structural and biochemical studies. The inhibitor was subjected to two point mutations at a conserved position, Asn14. This residue, known to have a pivotal role in stabilizing the first reactive-site loop (Gln63-Phe68) of the inhibitor, is highly conserved in the sequences of the other members of Kunitz (STI) family as well as in the sequences of Kazal family of serine protease inhibitors. The mutants, N14K and N14D, were subjected to biochemical assay and their characteristics were compared with those of the recombinant inhibitor (rWCI). Crystallographic studies of the recombinant and the mutant proteins are discussed. These studies were primarily aimed at understanding the importance of the protein scaffolding towards the conformational rigidity of the reactive-site loop. Our analysis reveals that, as the Lys14 side chain takes an unusual fold in N14K and the Asp14 side chain in N14D interacts with the loop residues by water-mediated hydrogen bonds, the canonical conformation of the loop has remained effectively intact in both the mutant structures. However, minor alterations such as a 2-fold increase in the inhibitory affinity towards the cognate enzyme were observed.

  • Organizational Affiliation

    Crystallography and Molecular Biology Division, Saha Institute of Nuclear Physics, 1/AF, Bidhan Nagar, Calcutta 700 064, India.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
CHYMOTRYPSIN INHIBITOR 3186Psophocarpus tetragonolobusMutation(s): 1 
Find proteins for P10822 (Psophocarpus tetragonolobus)
Explore P10822 
Go to UniProtKB:  P10822
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP10822
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 2.00 Å
  • R-Value Free: 0.287 
  • R-Value Work: 0.209 
  • R-Value Observed: 0.217 
  • Space Group: P 61 2 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 61.24α = 90
b = 61.24β = 90
c = 210.86γ = 120
Software Package:
Software NamePurpose
MOSFLMdata reduction
SCALAdata scaling
CCP4data scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2001-02-19
    Type: Initial release
  • Version 1.1: 2008-04-27
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Derived calculations, Version format compliance
  • Version 1.3: 2021-11-03
    Changes: Database references, Derived calculations