Crystal Structure of Infestin 4, a factor XIIa inhibitor

Experimental Data Snapshot

  • Resolution: 1.40 Å
  • R-Value Free: 0.190 
  • R-Value Work: 0.180 
  • R-Value Observed: 0.181 

Starting Model: experimental
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The Kazal-type inhibitors infestins 1 and 4 differ in specificity but are similar in three-dimensional structure.

Campos, I.T.Souza, T.A.Torquato, R.J.De Marco, R.Tanaka-Azevedo, A.M.Tanaka, A.S.Barbosa, J.A.R.G.

(2012) Acta Crystallogr D Biol Crystallogr 68: 695-702

  • DOI: https://doi.org/10.1107/S0907444912009067
  • Primary Citation of Related Structures:  
    2ERW, 2F3C

  • PubMed Abstract: 

    Blood coagulation is an important process in haemostasis, and disorders of blood coagulation can lead to an increased risk of haemorrhage and thrombosis. Coagulation is highly conserved in mammals and has been comprehensively studied in humans in the investigation of bleeding or thrombotic diseases. Some substances can act as inhibitors of blood coagulation and may affect one or multiple enzymes throughout the process. A specific thrombin inhibitor called infestin has been isolated from the midgut of the haematophagous insect Triatoma infestans. Infestin is a member of the nonclassical Kazal-type serine protease inhibitors and is composed of four domains, all of which have a short central α-helix and a small antiparallel β-sheet. Domains 1 and 4 of infestin (infestins 1 and 4) possess specific inhibitory activities. Infestin 1 inhibits thrombin, while infestin 4 is an inhibitor of factor XIIa, plasmin and factor Xa. Here, the structure determination and structural analysis of infestin 1 complexed with trypsin and of infestin 4 alone are reported. Through molecular modelling and docking, it is suggested that the protein-protein binding site is conserved in the infestin 1-thrombin complex compared with other Kazal-type inhibitors. Infestin 4 is able to bind factor XIIa, and the F9N and N11R mutants selected by phage display were shown to be more selective for factor XIIa in comparison to the wild type.

  • Organizational Affiliation

    Departamento de Bioquímica, Escola Paulista de Medicina, Universidade Federal de São Paulo, Rua Três de Maio 100, 04044-020 São Paulo-SP, Brazil.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
serine protease inhibitor infestin56Triatoma infestansMutation(s): 0 
Find proteins for Q95P16 (Triatoma infestans)
Explore Q95P16 
Go to UniProtKB:  Q95P16
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ95P16
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.40 Å
  • R-Value Free: 0.190 
  • R-Value Work: 0.180 
  • R-Value Observed: 0.181 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 25.765α = 90
b = 45.377β = 90
c = 56.771γ = 90
Software Package:
Software NamePurpose
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: 2006-10-31
    Type: Initial release
  • Version 1.1: 2008-05-01
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Advisory, Version format compliance
  • Version 1.3: 2012-06-20
    Changes: Database references
  • Version 1.4: 2017-07-05
    Changes: Database references
  • Version 1.5: 2023-08-23
    Changes: Data collection, Database references, Refinement description