View source for 9qk2


==Structure of the Complement classical and lectin pathway C3 convertase in complex with substrate C3==
<StructureSection load='9qk2' size='340' side='right'caption='[[9qk2]], [[Resolution|resolution]] 3.50&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[9qk2]] is a 7 chain structure with sequence from [https://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] and [https://en.wikipedia.org/wiki/Lama_glama Lama glama]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=9QK2 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=9QK2 FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">Electron Microscopy, [[Resolution|Resolution]] 3.5&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=MG:MAGNESIUM+ION'>MG</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=9qk2 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=9qk2 OCA], [https://pdbe.org/9qk2 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=9qk2 RCSB], [https://www.ebi.ac.uk/pdbsum/9qk2 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=9qk2 ProSAT]</span></td></tr>
</table>
== Disease ==
[https://www.uniprot.org/uniprot/CO4A_HUMAN CO4A_HUMAN] Defects in C4A are the cause of complement component 4A deficiency (C4AD) [MIM:[https://omim.org/entry/614380 614380]. A rare defect of the complement classical pathway associated with the development of autoimmune disorders, mainly systemic lupus with or without associated glomerulonephritis.<ref>PMID:8473511</ref>   Defects in C4A are a cause of susceptibility to systemic lupus erythematosus (SLE) [MIM:[https://omim.org/entry/152700 152700]. A chronic, inflammatory and often febrile multisystemic disorder of connective tissue. It affects principally the skin, joints, kidneys and serosal membranes. It is thought to represent a failure of the regulatory mechanisms of the autoimmune system. Note=Interindividual copy-number variation (CNV) of complement component C4 and associated polymorphisms result in different susceptibilities to SLE. The risk of SLE susceptibility has been shown to be significantly increased among subjects with only two copies of total C4. A high copy number is a protective factor against SLE.<ref>PMID:17503323</ref> 
== Function ==
[https://www.uniprot.org/uniprot/CO4A_HUMAN CO4A_HUMAN] C4 plays a central role in the activation of the classical pathway of the complement system. It is processed by activated C1 which removes from the alpha chain the C4a anaphylatoxin. The remaining alpha chain fragment C4b is the major activation product and is an essential subunit of the C3 convertase (C4b2a) and the C5 convertase (C3bC4b2a) enzymes of the classical complement pathway.  Derived from proteolytic degradation of complement C4, C4a 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.
== References ==
<references/>
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</StructureSection>
[[Category: Homo sapiens]]
[[Category: Lama glama]]
[[Category: Large Structures]]
[[Category: Brondijk THC]]
[[Category: De la O Becerra KI]]
[[Category: Gros P]]