2i6q

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spinqualitylabelsall models PDB ID 2i6q Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image
, resolution 2.100Å
Ligands:	, , , ,
Gene:	C2a (Homo sapiens)
Activity:	Classical-complement-pathway C3/C5 convertase, with EC number 3.4.21.43
Related:	2I6S
Resources:	FirstGlance, OCA, PDBsum, RCSB
Coordinates:	save as pdb, mmCIF, xml

Complement component C2a

Overview

C2a provides the catalytic center to the convertase complexes of the classical and lectin-binding pathways of complement activation. We determined two crystal structures of full-length C2a, with and without a pseudo ligand bound. Both structures reveal a near-active conformation of the catalytic center of the serine protease domains, while the von Willebrand factor A-type domains display an intermediate activation state of helix alpha7 with an open, activated metal-ion-dependent adhesion site. The open adhesion site likely serves to enhance the affinity for the ligand C4b, similar to "inside-out" signaling in integrins. Surprisingly, the N-terminal residues of C2a are buried in a crevice near helix alpha7, indicative of a structural switch between C2 and C2a. Extended loops on the protease domain possibly envelop the protruding anaphylatoxin domain of the substrate C3. Together with a putative substrate-induced completion of the oxyanion hole, this may contribute to the high substrate specificity of the convertases.

About this Structure

2I6Q is a Single protein structure of sequence from Homo sapiens. Full crystallographic information is available from OCA.

Reference

Structure of complement component C2A: implications for convertase formation and substrate binding., Milder FJ, Raaijmakers HC, Vandeputte MD, Schouten A, Huizinga EG, Romijn RA, Hemrika W, Roos A, Daha MR, Gros P, Structure. 2006 Oct;14(10):1587-97. PMID:17027507

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