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==Asymmetric complex of Factor XII and kininogen with gC1qR/C1QBP/P32 is governed by allostery==
<StructureSection load='6szw' size='340' side='right'caption='[[6szw]], [[Resolution|resolution]] 3.14&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[6szw]] is a 4 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=6SZW OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=6SZW 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]] 3.14&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=ZN:ZINC+ION'>ZN</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=6szw FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=6szw OCA], [https://pdbe.org/6szw PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=6szw RCSB], [https://www.ebi.ac.uk/pdbsum/6szw PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=6szw ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/C1QBP_HUMAN C1QBP_HUMAN] Is believed to be a multifunctional and multicompartmental protein involved in inflammation and infection processes, ribosome biogenesis, regulation of apoptosis, transcriptional regulation and pre-mRNA splicing. At the cell surface is thought to act as an endothelial receptor for plasma proteins of the complement and kallikrein-kinin cascades. Putative receptor for C1q; specifically binds to the globular "heads" of C1q thus inhibiting C1; may perform the receptor function through a complex with C1qR/CD93. In complex with cytokeratin-1/KRT1 is a high affinty receptor for kininogen-1/HMWK. Can also bind other plasma proteins, such as coagulation factor XII leading to its autoactivation. May function to bind initially fluid kininogen-1 to the cell membrane. The secreted form may enhance both extrinsic and intrinsic coagulation pathways. It is postulated that the cell surface form requires docking with transmembrane proteins for downstream signaling which might be specific for a cell-type or response. By acting as C1q receptor is involved in chemotaxis of immature dendritic cells and neutrophils and is proposed to signal through CD209/DC-SIGN on immature dendritic cells, through integrin alpha-4/beta-1 during trophoblast invasion of the decidua, and through integrin beta-1 during endothelial cell adhesion and spreading. Signaling involved in inhibition of innate immune response is implicating the PI3K-AKT/PKB pathway. In mitochondrial translation may be involved in formation of functional 55S mitoribosomes; the function seems to involve its RNA-binding activity. May be involved in the nucleolar ribosome maturation process; the function may involve the exchange of FBL for RRP1 in the association with pre-ribosome particles. Involved in regulation of RNA splicing by inhibiting the RNA-binding capacity of SRSF1 and its phosphorylation. Is required for the nuclear translocation of splicing factor U2AF1L4. Involved in regulation of CDKN2A- and HRK-mediated apoptosis. Stabilizes mitochondrial CDKN2A isoform smARF. May be involved in regulation of FOXC1 transcriptional activity and NFY/CCAAT-binding factor complex-mediated transcription. In infection processes acts as an attachment site for microbial proteins, including Listeria monocytogenes internalin B and Staphylococcus aureus protein A. May play a role in antibacterial defense as it can bind to cell surface hyaluronan and inhibit Streptococcus pneumoniae hyaluronate lyase. Involved in replication of Rubella virus. May be involved in modulation of the immune response; ligation by HCV core protein is resulting in suppresion of interleukin-12 production in monocyte-derived dendritic cells. Involved in regulation of antiviral response by inhibiting DDX58- and IFIH1-mediated signaling pathways probably involving its association with MAVS after viral infection. Involved in HIV-1 replication, presumably by contributing to splicing of viral RNA.<ref>PMID:8662673</ref> <ref>PMID:8710908</ref> <ref>PMID:9461517</ref> <ref>PMID:10479529</ref> <ref>PMID:10022843</ref> <ref>PMID:10747014</ref> <ref>PMID:10722602</ref> <ref>PMID:11086025</ref> <ref>PMID:11859136</ref> <ref>PMID:12833064</ref> <ref>PMID:15243141</ref> <ref>PMID:16177118</ref> <ref>PMID:16140380</ref> <ref>PMID:17881511</ref> <ref>PMID:18676636</ref> <ref>PMID:19004836</ref> <ref>PMID:19164550</ref> <ref>PMID:20810993</ref> <ref>PMID:21536856</ref> <ref>PMID:21544310</ref> <ref>PMID:22700724</ref> 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
The contact system is composed of Factor XII (FXII), prekallikrein (PK) and co-factor kininogen (HK). The globular C1q receptor (gC1qR) has been shown to interact with FXII and HK. We reveal the FXII fibronectin type II domain (FnII) binds gC1qR in a Zn2+ dependent fashion and determined the complex crystal structure. FXIIFnII binds the gC1qR trimer in an asymmetric fashion with residues Arg36 and Arg65 forming contacts with two distinct negatively charged pockets. gC1qR residues Asp185 and His187 coordinate a Zn2+ adjacent to the FXII binding site and a comparison with the ligand free gC1qR crystal structure reveals the anionic G1-loop becomes ordered upon FXIIFnII binding. Additional conformational changes in the region of the Zn2+ binding site reveal an allosteric basis for Zn2+ modulation of FXII binding. Mutagenesis coupled with SPR demonstrate the gC1qR Zn2+ site contributes to FXII binding and plasma based assays reveal gC1qR stimulates coagulation in a FXII-dependent manner. Analysis of the binding of HK domain 5 (HKD5) to gC1qR shows only one high affinity binding site per trimer. Mutagenesis studies identify a critical G3-loop located at the center of the gC1qR trimer suggesting steric occlusion as the mechanism for HKD5 asymmetric binding. Gel filtration experiments reveal that gC1qR clusters FXII and HK into a higher order 500kDa ternary complex. These results support the conclusion that extracellular gC1qR can act as a chaperone to cluster contact factors which may be a prelude for initiating the cascades which drive bradykinin generation and the intrinsic pathway of coagulation.

Factor XII and kininogen asymmetric assembly with gC1qR/C1QBP/P32 is governed by allostery.,Kaira BG, Slater A, McCrae KR, Dreveny I, Sumya UM, Mutch NJ, Searle M, Emsley J Blood. 2020 Jun 19. pii: 461064. doi: 10.1182/blood.2020004818. PMID:32559765<ref>PMID:32559765</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 6szw" style="background-color:#fffaf0;"></div>

==See Also==
*[[3D structures of FXII|3D structures of FXII]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Homo sapiens]]
[[Category: Large Structures]]
[[Category: Emsley J]]
[[Category: Kaira BG]]