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Complement component 3

 
Veterinary Dictionary: C3
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The third component of complement; a β protein. Split into two fragments, C3a and C3b, by C3 convertase which is triggered via the classical or alternative pathway of complement activation. An inherited deficiency occurs in Brittany spaniels and very low serum levels occur in some Finnish-Landrace lambs. See also complement.

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Complement component 3
PDB rendering based on 1c3d.
Available structures: 1c3d, 1ghq, 1w2s, 2a73, 2a74, 2b39, 2gox, 2hr0, 2i07, 2ice, 2icf
Identifiers
Symbols C3; ASP; CPAMD1
External IDs OMIM: 120700 MGI: 88227 HomoloGene: 68031
Orthologs
Human Mouse
Entrez 718 12266
Ensembl n/a ENSMUSG00000024164
Uniprot n/a Q207D2
Refseq NM_000064 (mRNA)
NP_000055 (protein)		 NM_009778 (mRNA)
NP_033908 (protein)
Location n/a Chr 17: 56.89 - 56.91 Mb
Pubmed search [1] [2]

Complement component 3, often simply called C3, is a protein of the immune system. It plays a central role in the complement system and contributes to innate immunity. In humans it is encoded on chromosome 19 by a gene called C3.[1][2]

Contents

Function

C3 plays a central role in the activation of complement system.[3] Its activation is required for both classical and alternative complement activation pathways. People with C3 deficiency are susceptible to bacteria infection.[4][5]

Soluble C3-convertase, also known as C4b2a, catalyzes the proteolytic cleavage of C3 into C3a and C3b as part of the classical complement system as well as the mannan-binding lectin pathway. C3a is an anaphylotoxin, and C3b serves as an opsonizing agent. Factor I can cleave C3b into C3c and C3d, the latter of which plays a role in enhancing B cell responses. In the alternative complement pathway, C3 is cleaved by iC3Bb, another form of C3-convertase.

Structure

Several crystallographic structures of C3 have been determined and reveal that this protein contains 13 domains.[6][7][8][9]

Clinical use

Levels of C3 in the blood may be measured to support or refute a particular medical diagnosis. For example, low C3 levels are associated with some types of kidney disease such as post-infectious glomerulonephritis and shunt nephritis.

Interactions

Complement component 3 has been shown to interact with Factor H.[10][11]

References

  1. ^ de Bruijn MH, Fey GH (February 1985). "Human complement component C3: cDNA coding sequence and derived primary structure". Proc. Natl. Acad. Sci. U.S.A. 82 (3): 708–12. doi:10.1073/pnas.82.3.708. PMID 2579379. PMC: 397115. http://www.pnas.org/content/82/3/708.abstract. 
  2. ^ "Entrez Gene: C3 complement component 3". http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=718. 
  3. ^ Sahu A, Lambris JD (April 2001). "Structure and biology of complement protein C3, a connecting link between innate and acquired immunity". Immunol. Rev. 180: 35–48. doi:10.1034/j.1600-065X.2001.1800103.x. PMID 11414361. 
  4. ^ Lachmann P (December 1975). "Genetics of the complement system". J. Med. Genet. 12 (4): 372–7. doi:10.1136/jmg.12.4.372. PMID 768477. 
  5. ^ Matsuyama W, Nakagawa M, Takashima H, Muranaga F, Sano Y, Osame M (December 2001). "Molecular analysis of hereditary deficiency of the third component of complement (C3) in two sisters" ([dead link] – Scholar search). Intern. Med. 40 (12): 1254–8. doi:10.2169/internalmedicine.40.1254. PMID 11813855. http://joi.jlc.jst.go.jp/JST.Journalarchive/internalmedicine1992/40.1254?from=PubMed. 
  6. ^ Janssen BJ, Huizinga EG, Raaijmakers HC, Roos A, Daha MR, Nilsson-Ekdahl K, Nilsson B, Gros P (September 2005). "Structures of complement component C3 provide insights into the function and evolution of immunity". Nature 437 (7058): 505–11. doi:10.1038/nature04005. PMID 16177781. 
  7. ^ Janssen BJ, Christodoulidou A, McCarthy A, Lambris JD, Gros P (November 2006). "Structure of C3b reveals conformational changes that underlie complement activity". Nature 444 (7116): 213–6. doi:10.1038/nature05172. PMID 17051160. 
  8. ^ Wiesmann C, Katschke KJ, Yin J, Helmy KY, Steffek M, Fairbrother WJ, McCallum SA, Embuscado L, DeForge L, Hass PE, van Lookeren Campagne M (November 2006). "Structure of C3b in complex with CRIg gives insights into regulation of complement activation". Nature 444 (7116): 217–20. doi:10.1038/nature05263. PMID 17051150. 
  9. ^ Fredslund F, Jenner L, Husted LB, Nyborg J, Andersen GR, Sottrup-Jensen L (August 2006). "The structure of bovine complement component 3 reveals the basis for thioester function". J. Mol. Biol. 361 (1): 115–27. doi:10.1016/j.jmb.2006.06.009. PMID 16831446. 
  10. ^ Soames, C J; Sim R B (Sep. 1997). "Interactions between human complement components factor H, factor I and C3b". Biochem. J. (ENGLAND) 326 ( Pt 2): 553-61. ISSN 0264-6021. PMID 9291131. 
  11. ^ Jokiranta, T S; Westin J, Nilsson U R, Nilsson B, Hellwage J, Löfås S, Gordon D L, Ekdahl K N, Meri S (Mar. 2001). "Complement C3b interactions studied with surface plasmon resonance technique". Int. Immunopharmacol. (Netherlands) 1 (3): 495-506. ISSN 1567-5769. PMID 11367533. 

External links

v • d • e
Proteins: complement system (C, L, A)
Activators/enzymes
Early
C: C1Q/C1R/C1S - C4 (C4a) - C2
L: MASP1/MASP2 - MBL
Middle
Late
CLA: MAC (C6, C7, C8, C9)
Inhibitors
Complement receptors
v • d • e
Acute phase proteins
Amyloid
Other positive
Negative
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Copyrights:

Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.  Read more
Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Complement component 3".  Read more