1PK6

Globular Head of the Complement System Protein C1q

Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.85 Å
  • R-Value Free: 0.239 
  • R-Value Work: 0.199 

wwPDB Validation 3D Report Full Report


This is version 1.3 of the entry. See complete history. 

Literature

The crystal structure of the globular head of complement protein C1q provides a basis for its versatile recognition properties.

Gaboriaud, C., Juanhuix, J., Gruez, A., Lacroix, M., Darnault, C., Pignol, D., Verger, D., Fontecilla-Camps, J.C., Arlaud, G.J.

(2003) J.Biol.Chem. 278: 46974-46982

  • DOI: 10.1074/jbc.M307764200

  • PubMed Abstract: 

    • C1q is a versatile recognition protein that binds to an amazing variety of immune and non-immune ligands and triggers activation of the classical pathway of complement. The crystal structure of the C1q globular domain responsible for its recognition ...

    C1q is a versatile recognition protein that binds to an amazing variety of immune and non-immune ligands and triggers activation of the classical pathway of complement. The crystal structure of the C1q globular domain responsible for its recognition properties has now been solved and refined to 1.9 A of resolution. The structure reveals a compact, almost spherical heterotrimeric assembly held together mainly by non-polar interactions, with a Ca2+ ion bound at the top. The heterotrimeric assembly of the C1q globular domain appears to be a key factor of the versatile recognition properties of this protein. Plausible three-dimensional models of the C1q globular domain in complex with two of its physiological ligands, C-reactive protein and IgG, are proposed, highlighting two of the possible recognition modes of C1q. The C1q/human IgG1 model suggests a critical role for the hinge region of IgG and for the relative orientation of its Fab domain in C1q binding.

    Organizational Affiliation: 

    Laboratoire de Cristallographie et Cristallogéncse des Protéines, Institut de Biologie Structurale Jean-Pierre Ebel, Commissariat à l'Energie Atomique (CEA)-CNRS-Université Joseph Fourier, 41 rue Jules Horowitz, 38027 Grenoble Cedex 1, France.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Complement C1q subcomponent, A chain precursor
A
133Homo sapiensMutation(s): 0 
Gene Names: C1QA
Find proteins for P02745 (Homo sapiens)
Go to Gene View: C1QA
Go to UniProtKB:  P02745
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetails
Complement C1q subcomponent, B chain precursor
B
132Homo sapiensMutation(s): 0 
Gene Names: C1QB
Find proteins for P02746 (Homo sapiens)
Go to Gene View: C1QB
Go to UniProtKB:  P02746
Entity ID: 3
MoleculeChainsSequence LengthOrganismDetails
Complement C1q subcomponent, C chain precursor
C
129Homo sapiensMutation(s): 0 
Gene Names: C1QC (C1QG)
Find proteins for P02747 (Homo sapiens)
Go to Gene View: C1QC
Go to UniProtKB:  P02747
Small Molecules
Ligands 1 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
CA
Query on CA
Download SDF File 
Download CCD File 
B
CALCIUM ION
Ca
BHPQYMZQTOCNFJ-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.85 Å
  • R-Value Free: 0.239 
  • R-Value Work: 0.199 
  • Space Group: C 1 2 1
Unit Cell:
Length (Å)Angle (°)
a = 80.182α = 90.00
b = 53.222β = 112.32
c = 90.880γ = 90.00
Software Package:
Software NamePurpose
CCP4data scaling
AMoREphasing
REFMACrefinement
XDSdata reduction

Structure Validation

View Full Validation Report or Ramachandran Plots


View more in-depth experimental data

Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2003-10-21
    Type: Initial release
  • Version 1.1: 2008-04-29
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance
  • Version 1.3: 2018-01-31
    Type: Advisory, Experimental preparation