Structural highlights
Disease
[CO2_HUMAN] Defects in C2 are the cause of complement component 2 deficiency (C2D) [MIM:217000]. A deficiency of the complement classical pathway associated with the development of autoimmune disorders, mainly systemic lupus erythematosus. Skin and joint manifestations are common and renal disease is relatively rare. Patients with complement component 2 deficiency are also reported to have recurrent or invasive infections.[1] [2]
Function
[CO2_HUMAN] Component C2 which is part of the classical pathway of the complement system is cleaved by activated factor C1 into two fragments: C2b and C2a. C2a, a serine protease, then combines with complement factor 4b to generate the C3 or C5 convertase.
Evolutionary Conservation
Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.
Publication Abstract from PubMed
The second component of complement (C2) is a multi-domain serine protease that provides catalytic activity for the C3 and C5 convertases of the classical and lectin pathways of human complement. The formation of these convertases requires the Mg(2+)-dependent binding of C2 to C4b and the subsequent cleavage of C2 by C1s or MASP2, respectively. The crystal structure of full-length C2 is not yet available, although the structure of its C-terminal catalytic segment C2a has been determined. The crystal structure of the N-terminal segment C2b of C2 determined to 1.8 A resolution presented here reveals the arrangement of its three CCP domains. The domains are arranged differently compared with most other CCP-domain assemblies, but their arrangement is similar to that found in the Ba part of the full-length factor B structure. The crystal structures of C2a, C2b and full-length factor B are used to generate a model for C2 and a discussion of the domain association and possible interactions with C4b during formation of the C4b-C2 complex is presented. The results of this study also suggest that upon cleavage by C1s, C2a domains undergo conformational rotation while bound to C4b and the released C2b domains may remain folded together similar to as observed in the intact protein.
The structure of C2b, a fragment of complement component C2 produced during C3 convertase formation.,Krishnan V, Xu Y, Macon K, Volanakis JE, Narayana SV Acta Crystallogr D Biol Crystallogr. 2009 Mar;65(Pt 3):266-74. Epub 2009, Feb 20. PMID:19237749[3]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Wetsel RA, Kulics J, Lokki ML, Kiepiela P, Akama H, Johnson CA, Densen P, Colten HR. Type II human complement C2 deficiency. Allele-specific amino acid substitutions (Ser189 --> Phe; Gly444 --> Arg) cause impaired C2 secretion. J Biol Chem. 1996 Mar 8;271(10):5824-31. PMID:8621452
- ↑ Zhu ZB, Atkinson TP, Volanakis JE. A novel type II complement C2 deficiency allele in an African-American family. J Immunol. 1998 Jul 15;161(2):578-84. PMID:9670930
- ↑ Krishnan V, Xu Y, Macon K, Volanakis JE, Narayana SV. The structure of C2b, a fragment of complement component C2 produced during C3 convertase formation. Acta Crystallogr D Biol Crystallogr. 2009 Mar;65(Pt 3):266-74. Epub 2009, Feb 20. PMID:19237749 doi:10.1107/S0907444909000389
