1PK6

Globular Head of the Complement System Protein C1q

Summary for 1PK6

• Entry DOI: 10.2210/pdb1pk6/pdb
• Related: 1ELV 1GPZ 1NZI
• Descriptor: Complement C1q subcomponent, A chain precursor, Complement C1q subcomponent, B chain precursor, Complement C1q subcomponent, C chain precursor, ... (5 entities in total)
• Functional Keywords: complement system, c1q, immunology, jellyroll, igg, immune system
• Biological source: Homo sapiens (human); More
• Cellular location: Secreted: P02745 P02746 P02747
• Total number of polymer chains: 3
• Total formula weight: 44253.08

Authors

Gaboriaud, C.,Juanhuix, J.,Gruez, A.,Lacroix, M.,Darnault, C.,Pignol, D.,Verger, D.,Fontecilla-Camps, J.C.,Arlaud, G.J. (deposition date: 2003-06-05, release date: 2003-10-21, Last modification date: 2024-10-30)

Primary citation

Gaboriaud, C.,Juanhuix, J.,Gruez, A.,Lacroix, M.,Darnault, C.,Pignol, D.,Verger, D.,Fontecilla-Camps, J.C.,Arlaud, G.J.
The crystal structure of the globular head of complement protein C1q provides a basis for its versatile recognition properties.
J.Biol.Chem., 278:46974-46982, 2003

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 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.

PubMed: 12960167
DOI: 10.1074/jbc.M307764200

Experimental method

X-RAY DIFFRACTION (1.85 Å)