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Function
Complement C3 (CC3) activates the complement system which is part of the immune response. CC3 is proteolytically cleaved by C3 convertase to C3a (residues 672-748) and C3b (residues 23-667, 749-1663). C3a is a mediator of local inflammatory processes. C3b binds covalently to cell surface carbohydrates or immune aggregates. Breakdown of C3b generates the fragment C3d (residues 996-1287) which binds to antigens enhancing their uptake by B cells. C3c is another C3b cleavage product residues: 23-664, 749-954, 1321-1663.[1]
Disease
A mutation in CC3 cause the progressive kidney disease: dense deposit disease. Other mutations are associated with recurrent bacterial infections.
Relevance
Low levels of CC3 in the blood are associated with some kidney diseases.
- ↑ Sahu A, Lambris JD. Structure and biology of complement protein C3, a connecting link between innate and acquired immunity. Immunol Rev. 2001 Apr;180:35-48. PMID:11414361
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3D structures of complement C3
Updated on 14-December-2015
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- Complement C3
- 2a73 – hCC3 – human
- 1ghq – hCC3 residues 996-1300 + Epstein-Barr virus receptor
- 2b39 – bCC3 – bovine
- Complement C3a (anaphylatoxin)
- Complement C3b
- 2hr0, 2i07 – hCC3 β+α’ chains
- 2icf – hCC3 α+β chains + protein CRIG
- 3g6j – hCC3 α+β chains + antibody
- 2xwb – hCC3 α+β chains + complement factor B + complement factor D
- 2xwj – hCC3 α+β chains (mutant) + complement factor B
- 2wii – hCC3 α+β chains + complement factor H 1-4 sushi domains
- 3l5n, 3ohx – hCC3 α+β chains + staphylococcal complement inhibitor
- 2win – hCC3 α+β chains + complement factor B BB fragment + staphylococcal complement inhibitor
- Complement C3c
- 2a74 – hCC3
- 2qki – hCC3 + compstatin
- 3l3o, 3nms – hCC3 + staphylococcal complement inhibitor
- 2ice – hCC3 α+β chains + protein CRIG
- 3t4a – hCC3 α+β chains + fibrinogen-binding protein
- Complement C3d
- 1c3d – hCC3 (mutant)
- 1w2s, 3oed – hCC3 1-2 sushi domains + complement receptor type 2 precursor
- 2gox, 3d5r, 3d5s – hCC3 α chain fragment + fibrinogen-binding protein
- 2noj – hCC3 α chain fragment (mutant) + EFB homologous protein
- 2wy7, 2wy8 – hCC3 α chain fragment (mutant) + IGG-binding protein
- 3oxu – hCC3 α chain fragment (mutant) + HF protein
- 4m76 – hCC3 α chain fragment (mutant) + integrin α-M
- 2xqw – hCC3 + complement factor H 19-20 sushi domains
- 3rj3 – hCC3 α chain fragment + complement factor H-related protein
- 1qqf – rCC3 G fragment - rat
- 1qsj – rCC3 G fragment (mutant)
References
proteopedia link