Crystal structure of anionic trypsin isoform 3 from chum salmon

Experimental Data Snapshot

  • Resolution: 1.55 Å
  • R-Value Free: 0.196 
  • R-Value Work: 0.186 

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A structural comparison of three isoforms of anionic trypsin from chum salmon (Oncorhynchus keta).

Toyota, E.Iyaguchi, D.Sekizaki, H.Tateyama, M.Ng, K.K.

(2009) Acta Crystallogr D Biol Crystallogr 65: 717-723

  • DOI: https://doi.org/10.1107/S0907444909012165
  • Primary Citation of Related Structures:  
    2ZPQ, 2ZPR, 2ZPS

  • PubMed Abstract: 

    Three anionic salmon trypsin isoforms (CST-1, CST-2 and CST-3) were isolated from the pyloric caeca of chum salmon (Oncorhynchus keta). The order of catalytic efficiency (K(m)/k(cat)) of the isoforms during BAPA hydrolysis was CST-2 > CST-1 > CST-3. In order to find a structural rationalization for the observed difference in catalytic efficiency, the X-ray crystallographic structures of the three isoforms were compared in detail. Some structural differences were observed in the C-terminal alpha-helix, interdomain loop and active-site region. From the results of the detailed comparison, it appears that the structural flexibility of the C-terminal alpha-helix, which interacts with the N-terminal domain, and the substrate-binding pocket in CST-3 are lower than those in CST-1 and CST-2. In addition, the conformation of the catalytic triad (His57, Asp102 and Ser195) differs among the three isoforms. The imidazole N atom of His57 in CST-1 and CST-2 forms a hydrogen bond to the hydroxyl O atom of Ser195, but the distance between the imidazole N atom of His57 and the hydroxyl O atom of Ser195 in CST-3 is too great (3.8 A) for the formation of a hydrogen bond. Thus, the nucleophilicity of the hydroxyl group of Ser195 in CST-3 is weaker than that in CST-1 or CST-2. Furthermore, the electrostatic potential of the substrate-binding pocket in CST-2 is markedly lower than those in CST-1 and CST-3 owing to the negative charges of Asp150, Asp153 and Glu221B that arise from the long-range effect. These results may explain the higher catalytic efficiency of CST-2 compared with CST-1 and CST-3.

  • Organizational Affiliation

    Faculty of Pharmaceutical Sciences, Health Sciences University of Hokkaido, Japan. toyota@hoku-iryo-u.ac.jp

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Anionic trypsin222Oncorhynchus ketaMutation(s): 0 
Find proteins for B3Y8K6 (Oncorhynchus keta)
Explore B3Y8K6 
Go to UniProtKB:  B3Y8K6
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupB3Y8K6
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.55 Å
  • R-Value Free: 0.196 
  • R-Value Work: 0.186 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 44.371α = 90
b = 47.531β = 90
c = 81.508γ = 90
Software Package:
Software NamePurpose
CrystalCleardata 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: 2009-07-28
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Version format compliance
  • Version 1.2: 2016-09-28
    Changes: Other