Experimental Data Snapshot

  • Resolution: 1.20 Å
  • R-Value Free: 0.225 
  • R-Value Observed: 0.179 

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This is version 1.3 of the entry. See complete history


The 1.2 A crystal structure of hirustasin reveals the intrinsic flexibility of a family of highly disulphide-bridged inhibitors.

Uson, I.Sheldrick, G.M.de La Fortelle, E.Bricogne, G.Di Marco, S.Priestle, J.P.Grutter, M.G.Mittl, P.R.

(1999) Structure 7: 55-63

  • DOI: https://doi.org/10.1016/s0969-2126(99)80009-4
  • Primary Citation of Related Structures:  
    1BX7, 1BX8

  • PubMed Abstract: 

    Leech-derived inhibitors have a prominent role in the development of new antithrombotic drugs, because some of them are able to block the blood coagulation cascade. Hirustasin, a serine protease inhibitor from the leech Hirudo medicinalis, binds specifically to tissue kallikrein and possesses structural similarity with antistasin, a potent factor Xa inhibitor from Haementeria officinalis. Although the 2.4 A structure of the hirustasin-kallikrein complex is known, classical methods such as molecular replacement were not successful in solving the structure of free hirustasin. Ab initio real/reciprocal space iteration has been used to solve the structure of free hirustasin using either 1.4 A room temperature data or 1.2 A low temperature diffraction data. The structure was also solved independently from a single pseudo-symmetric gold derivative using maximum likelihood methods. A comparison of the free and complexed structures reveals that binding to kallikrein causes a hinge-bending motion between the two hirustasin subdomains. This movement is accompanied by the isomerisation of a cis proline to the trans conformation and a movement of the P3, P4 and P5 residues so that they can interact with the cognate protease. The inhibitors from this protein family are fairly flexible despite being highly cross-linked by disulphide bridges. This intrinsic flexibility is necessary to adopt a conformation that is recognised by the protease and to achieve an optimal fit, such observations illustrate the pitfalls of designing inhibitors based on static lock-and-key models. This work illustrates the potential of new methods of structure solution that require less or even no prior phase information.

  • Organizational Affiliation

    Institut für Anorganische Chemie der Universität, Tammannstrasse 4, D-37077 Göttingen, Germany.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
HIRUSTASIN55Hirudo medicinalisMutation(s): 0 
Find proteins for P80302 (Hirudo medicinalis)
Explore P80302 
Go to UniProtKB:  P80302
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP80302
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.20 Å
  • R-Value Free: 0.225 
  • R-Value Observed: 0.179 
  • Space Group: P 43 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 37.713α = 90
b = 37.713β = 90
c = 67.812γ = 90
Software Package:
Software NamePurpose
MARXDSdata collection
MARSCALEdata reduction
SHELXL-97model building
MARXDSdata reduction
MARSCALEdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 1999-04-27
    Type: Initial release
  • Version 1.1: 2008-03-24
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2024-06-05
    Changes: Data collection, Database references, Derived calculations, Other