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From Proteopedia
The mouse von Willebrand Factor A1-botrocetin complex
Structural highlights
Function[LECBA_BOTJA] Snaclec that activates platelets by targeting vWF/GPIb. Two-chain botrocetin forms an activated complex with vWF (by binding the A1 domain), and the complex then binds to platelet glycoprotein Ibalpha (GP1BA), resulting in platelet aggregation. There are two distinct forms of the von Willebrand factor-dependent platelet coagglutinin. The dimeric form is 34-times more active than the one-chain botrocetin in promoting vWF binding to platelets. [VWF_MOUSE] Important in the maintenance of hemostasis, it promotes adhesion of platelets to the sites of vascular injury by forming a molecular bridge between sub-endothelial collagen matrix and platelet-surface receptor complex GPIb-IX-V. Also acts as a chaperone for coagulation factor VIII, delivering it to the site of injury, stabilizing its heterodimeric structure and protecting it from premature clearance from plasma (By similarity).[UniProtKB:P04275] [LECBB_BOTJA] Snaclec that activates platelets by targeting vWF/GPIb. Two-chain botrocetin forms an activated complex with vWF (by binding the A1 domain), and the complex then binds to platelet glycoprotein Ibalpha (GP1BA), resulting in platelet aggregation. There are two distinct forms of the von Willebrand factor-dependent platelet coagglutinin. The dimeric form is 34-times more active than the one-chain botrocetin in promoting vWF binding to platelets. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedBotrocetin is a snake venom protein that enhances the affinity of the A1 domain of plasma von Willebrand factor (vWF) for the platelet receptor glycoprotein Ibalpha (GPIbalpha), an event that contributes to bleeding and host death. Here we describe a kinetic and crystallographic analysis of this interaction that reveals a novel mechanism of affinity enhancement. Using high-temporal-resolution microscopy, we show that botrocetin decreases the GPIbalpha off-rate two-fold in both human and mouse complexes without affecting the on-rate. The key to this behavior is that, upon binding of GPIbalpha to vWF-A1, botrocetin prebound to vWF-A1 makes no contacts initially with GPIbalpha, but subsequently slides around the A1 surface to form a new interface. This two-step mechanism and flexible coupling may prevent adverse alterations in on-rate of GPIbalpha for vWF-A1, and permit adaptation to structural differences in GPIbalpha and vWF in several prey species. The snake venom protein botrocetin acts as a biological brace to promote dysfunctional platelet aggregation.,Fukuda K, Doggett T, Laurenzi IJ, Liddington RC, Diacovo TG Nat Struct Mol Biol. 2005 Feb;12(2):152-9. Epub 2005 Jan 16. PMID:15665869[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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