View source for 2xwj


==Crystal Structure of Complement C3b in Complex with Factor B==
<StructureSection load='2xwj' size='340' side='right'caption='[[2xwj]], [[Resolution|resolution]] 4.00&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[2xwj]] is a 12 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=2XWJ OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=2XWJ 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]] 4&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=NAG:N-ACETYL-D-GLUCOSAMINE'>NAG</scene>, <scene name='pdbligand=NI:NICKEL+(II)+ION'>NI</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=2xwj FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=2xwj OCA], [https://pdbe.org/2xwj PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=2xwj RCSB], [https://www.ebi.ac.uk/pdbsum/2xwj PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=2xwj 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> 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Activation of the complement cascade induces inflammatory responses and marks cells for immune clearance. In the central complement-amplification step, a complex consisting of surface-bound C3b and factor B is cleaved by factor D to generate active convertases on targeted surfaces. We present crystal structures of the pro-convertase C3bB at 4 angstrom resolution and its complex with factor D at 3.5 angstrom resolution. Our data show how factor B binding to C3b forms an open "activation" state of C3bB. Factor D specifically binds the open conformation of factor B through a site distant from the catalytic center and is activated by the substrate, which displaces factor D's self-inhibitory loop. This concerted proteolytic mechanism, which is cofactor-dependent and substrate-induced, restricts complement amplification to C3b-tagged target cells.

Structures of C3b in complex with factors B and D give insight into complement convertase formation.,Forneris F, Ricklin D, Wu J, Tzekou A, Wallace RS, Lambris JD, Gros P Science. 2010 Dec 24;330(6012):1816-20. PMID:21205667<ref>PMID:21205667</ref>

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

==See Also==
*[[Complement C3 3D structures|Complement C3 3D structures]]
*[[Complement factor 3D structures|Complement factor 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Homo sapiens]]
[[Category: Large Structures]]
[[Category: Forneris F]]
[[Category: Gros P]]
[[Category: Lambris JD]]
[[Category: Ricklin D]]
[[Category: Tzekou A]]
[[Category: Wallace RS]]
[[Category: Wu J]]