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==Cryo-EM structure of POmAb, a Type-I anti-prothrombin antiphospholipid antibody, bound to kringle-1 of human prothrombin==
<StructureSection load='8uf7' size='340' side='right'caption='[[8uf7]], [[Resolution|resolution]] 3.20&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[8uf7]] is a 3 chain structure with sequence from [https://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] and [https://en.wikipedia.org/wiki/Mus_musculus Mus musculus]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=8UF7 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=8UF7 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]] 3.2&#8491;</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=8uf7 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=8uf7 OCA], [https://pdbe.org/8uf7 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=8uf7 RCSB], [https://www.ebi.ac.uk/pdbsum/8uf7 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=8uf7 ProSAT]</span></td></tr>
</table>
== Disease ==
[https://www.uniprot.org/uniprot/THRB_HUMAN THRB_HUMAN] Defects in F2 are the cause of factor II deficiency (FA2D) [MIM:[https://omim.org/entry/613679 613679]. It is a very rare blood coagulation disorder characterized by mucocutaneous bleeding symptoms. The severity of the bleeding manifestations correlates with blood factor II levels.<ref>PMID:14962227</ref> <ref>PMID:6405779</ref> <ref>PMID:3771562</ref> <ref>PMID:3567158</ref> <ref>PMID:3801671</ref> <ref>PMID:3242619</ref> <ref>PMID:2719946</ref> <ref>PMID:1354985</ref> <ref>PMID:1421398</ref> <ref>PMID:1349838</ref> <ref>PMID:7865694</ref> <ref>PMID:7792730</ref>   Genetic variations in F2 may be a cause of susceptibility to ischemic stroke (ISCHSTR) [MIM:[https://omim.org/entry/601367 601367]; also known as cerebrovascular accident or cerebral infarction. A stroke is an acute neurologic event leading to death of neural tissue of the brain and resulting in loss of motor, sensory and/or cognitive function. Ischemic strokes, resulting from vascular occlusion, is considered to be a highly complex disease consisting of a group of heterogeneous disorders with multiple genetic and environmental risk factors.<ref>PMID:15534175</ref>   Defects in F2 are the cause of thrombophilia due to thrombin defect (THPH1) [MIM:[https://omim.org/entry/188050 188050]. It is a multifactorial disorder of hemostasis characterized by abnormal platelet aggregation in response to various agents and recurrent thrombi formation. Note=A common genetic variation in the 3-prime untranslated region of the prothrombin gene is associated with elevated plasma prothrombin levels and an increased risk of venous thrombosis.  Defects in F2 are associated with susceptibility to pregnancy loss, recurrent, type 2 (RPRGL2) [MIM:[https://omim.org/entry/614390 614390]. A common complication of pregnancy, resulting in spontaneous abortion before the fetus has reached viability. The term includes all miscarriages from the time of conception until 24 weeks of gestation. Recurrent pregnancy loss is defined as 3 or more consecutive spontaneous abortions.<ref>PMID:11506076</ref> 
== Function ==
[https://www.uniprot.org/uniprot/THRB_HUMAN THRB_HUMAN] Thrombin, which cleaves bonds after Arg and Lys, converts fibrinogen to fibrin and activates factors V, VII, VIII, XIII, and, in complex with thrombomodulin, protein C. Functions in blood homeostasis, inflammation and wound healing.<ref>PMID:2856554</ref> 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Antiprothrombin antibodies are found in antiphospholipid patients, but how they interact with prothrombin remains elusive. Prothrombin adopts closed and open forms. We recently discovered type I and type II antibodies and proposed that type I recognizes the open form. In this study, we report the discovery and structural and functional characterization in human plasma of a type I antibody, POmAb (prothrombin open monoclonal antibody). Using surface plasmon resonance and single-molecule spectroscopy, we show that POmAb interacts with kringle-1 of prothrombin, shifting the equilibrium toward the open form. Using single-particle cryogenic electron microscopy (cryo-EM), we establish that the epitope targeted by POmAb is in kringle-1, comprising an extended binding interface centered at residues R90-Y93. The 3.2-A cryo-EM structure of the complex reveals that the epitope overlaps with the position occupied by the protease domain of prothrombin in the closed state, explaining the exclusive binding of POmAb to the open form. In human plasma, POmAb prolongs phospholipid-initiated and diluted Russell's viper venom clotting time, which could be partly rescued by excess phospholipids, indicating POmAb is an anticoagulant but exerts a weak lupus anticoagulant effect. These studies reveal the structural basis of prothrombin recognition by a type I antiphospholipid antibody and uncover an exciting new strategy to achieve anticoagulation in human plasma.

Cryo-EM structure and functional basis of prothrombin recognition by a type I antiprothrombin antiphospholipid antibody.,Kumar S, Summers B, Basore K, Pengo V, Flaumenhaft R, Pozzi N Blood. 2024 May 9;143(19):2005-2011. doi: 10.1182/blood.2023022942. PMID:38437497<ref>PMID:38437497</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 8uf7" style="background-color:#fffaf0;"></div>
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Homo sapiens]]
[[Category: Large Structures]]
[[Category: Mus musculus]]
[[Category: Basore K]]
[[Category: Kumar S]]
[[Category: Pozzi N]]
[[Category: Summers B]]