A simplified BPTI variant containing 22 alanines out of 58 residues

Experimental Data Snapshot

  • Resolution: 1.60 Å
  • R-Value Free: 0.194 
  • R-Value Work: 0.167 
  • R-Value Observed: 0.169 

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Crystal structures of highly simplified BPTIs provide insights into hydration-driven increase of unfolding enthalpy

Islam, M.M.Yohda, M.Kidokoro, S.Kuroda, Y.

(2017) Sci Rep 7: 41205-41205

  • DOI: https://doi.org/10.1038/srep41205
  • Primary Citation of Related Structures:  
    5JB4, 5JB5, 5JB6, 5JB7

  • PubMed Abstract: 

    We report a thermodynamic and structural analysis of six extensively simplified bovine pancreatic trypsin inhibitor (BPTI) variants containing 19-24 alanines out of 58 residues. Differential scanning calorimetry indicated a two-state thermal unfolding, typical of a native protein with densely packed interior. Surprisingly, increasing the number of alanines induced enthalpy stabilization, which was however over-compensated by entropy destabilization. X-ray crystallography indicated that the alanine substitutions caused the recruitment of novel water molecules facilitating the formation of protein-water hydrogen bonds and improving the hydration shells around the alanine's methyl groups, both of which presumably contributed to enthalpy stabilization. There was a strong correlation between the number of water molecules and the thermodynamic parameters. Overall, our results demonstrate that, in contrast to our initial expectation, a protein sequence in which over 40% of the residues are alanines can retain a densely packed structure and undergo thermal denaturation with a large enthalpy change, mainly contributed by hydration.

  • Organizational Affiliation

    Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, 2-24-16 Nakamachi, Koganei-shi, Tokyo 184-8588, Japan.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Pancreatic trypsin inhibitor
A, B, C
58Bos taurusMutation(s): 19 
Find proteins for P00974 (Bos taurus)
Explore P00974 
Go to UniProtKB:  P00974
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP00974
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.60 Å
  • R-Value Free: 0.194 
  • R-Value Work: 0.167 
  • R-Value Observed: 0.169 
  • Space Group: C 2 2 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 60.989α = 90
b = 99.184β = 90
c = 61.731γ = 90
Software Package:
Software NamePurpose
DENZOdata reduction
SCALAdata scaling

Structure Validation

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Entry History 

Deposition Data

  • Released Date: 2017-04-19 
  • Deposition Author(s): Islam, M.M.

Revision History  (Full details and data files)

  • Version 1.0: 2017-04-19
    Type: Initial release
  • Version 1.1: 2020-02-19
    Changes: Data collection
  • Version 1.2: 2023-11-08
    Changes: Data collection, Database references, Refinement description