Complement inhibitor CirpA3 from Rhipicephalus pulchellus

Experimental Data Snapshot

  • Resolution: 2.10 Å
  • R-Value Free: 0.250 
  • R-Value Work: 0.217 
  • R-Value Observed: 0.222 

wwPDB Validation   3D Report Full Report

This is version 1.1 of the entry. See complete history


Structure and function of a family of tick-derived complement inhibitors targeting properdin.

Braunger, K.Ahn, J.Jore, M.M.Johnson, S.Tang, T.T.L.Pedersen, D.V.Andersen, G.R.Lea, S.M.

(2022) Nat Commun 13: 317-317

  • DOI: https://doi.org/10.1038/s41467-021-27920-2
  • Primary Citation of Related Structures:  
    7B26, 7B28, 7B29, 7B2A, 7B2D

  • PubMed Abstract: 

    Activation of the serum-resident complement system begins a cascade that leads to activation of membrane-resident complement receptors on immune cells, thus coordinating serum and cellular immune responses. Whilst many molecules act to control inappropriate activation, Properdin is the only known positive regulator of the human complement system. By stabilising the alternative pathway C3 convertase it promotes complement self-amplification and persistent activation boosting the magnitude of the serum complement response by all triggers. In this work, we identify a family of tick-derived alternative pathway complement inhibitors, hereafter termed CirpA. Functional and structural characterisation reveals that members of the CirpA family directly bind to properdin, inhibiting its ability to promote complement activation, and leading to potent inhibition of the complement response in a species specific manner. We provide a full functional and structural characterisation of a properdin inhibitor, opening avenues for future therapeutic approaches.

  • Organizational Affiliation

    Sir William Dunn School of Pathology, University of Oxford, OX1 3RE, Oxford, UK.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
CirpA3165Rhipicephalus pulchellusMutation(s): 0 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 1 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on SO4

Download Ideal Coordinates CCD File 
O4 S
Experimental Data & Validation

Experimental Data

  • Resolution: 2.10 Å
  • R-Value Free: 0.250 
  • R-Value Work: 0.217 
  • R-Value Observed: 0.222 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 68.366α = 90
b = 150.298β = 91.833
c = 68.43γ = 90
Software Package:
Software NamePurpose
XDSdata reduction
Aimlessdata scaling
Cootmodel building

Structure Validation

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Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
Wellcome TrustUnited Kingdom100298
Wellcome TrustUnited Kingdom209194
Wellcome TrustUnited Kingdom219477
Medical Research Council (MRC, United Kingdom)United KingdomS021264
European Molecular Biology Organization (EMBO)United KingdomALTF 554-2019

Revision History  (Full details and data files)

  • Version 1.0: 2021-12-08
    Type: Initial release
  • Version 1.1: 2022-02-02
    Changes: Database references