View source for 2a73


==Human Complement Component C3==
<StructureSection load='2a73' size='340' side='right'caption='[[2a73]], [[Resolution|resolution]] 3.30&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[2a73]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2A73 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=2A73 FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 3.3&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=BMA:BETA-D-MANNOSE'>BMA</scene>, <scene name='pdbligand=MAN:ALPHA-D-MANNOSE'>MAN</scene>, <scene name='pdbligand=NAG:N-ACETYL-D-GLUCOSAMINE'>NAG</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=2a73 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=2a73 OCA], [https://pdbe.org/2a73 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=2a73 RCSB], [https://www.ebi.ac.uk/pdbsum/2a73 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=2a73 ProSAT]</span></td></tr>
</table>
== Disease ==
[https://www.uniprot.org/uniprot/CO3_HUMAN CO3_HUMAN] Defects in C3 are the cause of complement component 3 deficiency (C3D) [MIM:[https://omim.org/entry/613779 613779]. A rare defect of the complement classical pathway. Patients develop recurrent, severe, pyogenic infections because of ineffective opsonization of pathogens. Some patients may also develop autoimmune disorders, such as arthralgia and vasculitic rashes, lupus-like syndrome and membranoproliferative glomerulonephritis.<ref>PMID:19913840</ref> <ref>PMID:9596584</ref> <ref>PMID:11387479</ref> <ref>PMID:15713468</ref> <ref>PMID:7961791</ref> [:]  Genetic variation in C3 is associated with susceptibility to age-related macular degeneration type 9 (ARMD9) [MIM:[https://omim.org/entry/611378 611378]. ARMD is a multifactorial eye disease and the most common cause of irreversible vision loss in the developed world. In most patients, the disease is manifest as ophthalmoscopically visible yellowish accumulations of protein and lipid that lie beneath the retinal pigment epithelium and within an elastin-containing structure known as Bruch membrane.<ref>PMID:19913840</ref> <ref>PMID:17634448</ref>   Defects in C3 are a cause of susceptibility to hemolytic uremic syndrome atypical type 5 (AHUS5) [MIM:[https://omim.org/entry/612925 612925]. An atypical form of hemolytic uremic syndrome. It is a complex genetic disease characterized by microangiopathic hemolytic anemia, thrombocytopenia, renal failure and absence of episodes of enterocolitis and diarrhea. In contrast to typical hemolytic uremic syndrome, atypical forms have a poorer prognosis, with higher death rates and frequent progression to end-stage renal disease. Note=Susceptibility to the development of atypical hemolytic uremic syndrome can be conferred by mutations in various components of or regulatory factors in the complement cascade system. Other genes may play a role in modifying the phenotype.<ref>PMID:19913840</ref> <ref>PMID:18796626</ref> <ref>PMID:20513133</ref>   Note=Increased levels of C3 and its cleavage product ASP, are associated with obesity, diabetes and coronary heart disease. Short-term endurance training reduces baseline ASP levels and subsequently fat storage.<ref>PMID:19913840</ref> 
== Function ==
[https://www.uniprot.org/uniprot/CO3_HUMAN CO3_HUMAN] C3 plays a central role in the activation of the complement system. Its processing by C3 convertase is the central reaction in both classical and alternative complement pathways. After activation C3b can bind covalently, via its reactive thioester, to cell surface carbohydrates or immune aggregates.<ref>PMID:8376604</ref> <ref>PMID:2909530</ref> <ref>PMID:9059512</ref> <ref>PMID:9555951</ref> <ref>PMID:10432298</ref> <ref>PMID:15833747</ref> <ref>PMID:16333141</ref> <ref>PMID:19615750</ref>   Derived from proteolytic degradation of complement C3, C3a anaphylatoxin is a mediator of local inflammatory process. It induces the contraction of smooth muscle, increases vascular permeability and causes histamine release from mast cells and basophilic leukocytes.<ref>PMID:8376604</ref> <ref>PMID:2909530</ref> <ref>PMID:9059512</ref> <ref>PMID:9555951</ref> <ref>PMID:10432298</ref> <ref>PMID:15833747</ref> <ref>PMID:16333141</ref> <ref>PMID:19615750</ref>   Acylation stimulating protein (ASP): adipogenic hormone that stimulates triglyceride (TG) synthesis and glucose transport in adipocytes, regulating fat storage and playing a role in postprandial TG clearance. Appears to stimulate TG synthesis via activation of the PLC, MAPK and AKT signaling pathways. Ligand for GPR77. Promotes the phosphorylation, ARRB2-mediated internalization and recycling of GPR77.<ref>PMID:8376604</ref> <ref>PMID:2909530</ref> <ref>PMID:9059512</ref> <ref>PMID:9555951</ref> <ref>PMID:10432298</ref> <ref>PMID:15833747</ref> <ref>PMID:16333141</ref> <ref>PMID:19615750</ref> 
== Evolutionary Conservation ==
[[Image:Consurf_key_small.gif|200px|right]]
Check<jmol>
  <jmolCheckbox>
    <scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/a7/2a73_consurf.spt"</scriptWhenChecked>
    <scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview03.spt</scriptWhenUnchecked>
    <text>to colour the structure by Evolutionary Conservation</text>
  </jmolCheckbox>
</jmol>, as determined by [http://consurfdb.tau.ac.il/ ConSurfDB]. You may read the [[Conservation%2C_Evolutionary|explanation]] of the method and the full data available from [http://bental.tau.ac.il/new_ConSurfDB/main_output.php?pdb_ID=2a73 ConSurf].
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== Publication Abstract from PubMed ==
The mammalian complement system is a phylogenetically ancient cascade system that has a major role in innate and adaptive immunity. Activation of component C3 (1,641 residues) is central to the three complement pathways and results in inflammation and elimination of self and non-self targets. Here we present crystal structures of native C3 and its final major proteolytic fragment C3c. The structures reveal thirteen domains, nine of which were unpredicted, and suggest that the proteins of the alpha2-macroglobulin family evolved from a core of eight homologous domains. A double mechanism prevents hydrolysis of the thioester group, essential for covalent attachment of activated C3 to target surfaces. Marked conformational changes in the alpha-chain, including movement of a critical interaction site through a ring formed by the domains of the beta-chain, indicate an unprecedented, conformation-dependent mechanism of activation, regulation and biological function of C3.

Structures of complement component C3 provide insights into the function and evolution of immunity.,Janssen BJ, Huizinga EG, Raaijmakers HC, Roos A, Daha MR, Nilsson-Ekdahl K, Nilsson B, Gros P Nature. 2005 Sep 22;437(7058):505-11. PMID:16177781<ref>PMID:16177781</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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<div class="pdbe-citations 2a73" style="background-color:#fffaf0;"></div>

==See Also==
*[[Complement C3 3D structures|Complement C3 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Homo sapiens]]
[[Category: Large Structures]]
[[Category: Daha MR]]
[[Category: Gros P]]
[[Category: Huizinga EG]]
[[Category: Janssen BJC]]
[[Category: Nilsson B]]
[[Category: Nilsson-Ekdahl K]]
[[Category: Raaijmakers HCA]]
[[Category: Roos A]]