1pk6
From Proteopedia
Globular Head of the Complement System Protein C1q
Overview
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.
About this Structure
1PK6 is a Protein complex structure of sequences from Homo sapiens. Full crystallographic information is available from OCA.
Reference
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 JC, Arlaud GJ, J Biol Chem. 2003 Nov 21;278(47):46974-82. Epub 2003 Sep 5. PMID:12960167 Page seeded by OCA on Sat May 3 05:10:51 2008
