Rhodocytin, a functional novel platelet agonist belonging to the heterodimeric C-type lectin family, induces platelet aggregation independently of glycoprotein Ib.
We isolated and characterized a functionally novel platelet agonist, designated as rhodocytin, from the Calloselasma rhodostoma venom. Rhodocytin was a disulfide-linked heterodimer consisting of 18- and 15-kDa subunits. The respective N-terminal amino acid sequences of both subunits were homologous to each other and to those of the carbohydrate-recognition domains (CRD) of C-type lectins. Rhodocytin alone induced platelet aggregation. Platelet agonists and antagonists constructed with CRD-like subunits from snake venoms bind to glycoprotein Ib directly or indirectly. However, rhodocytin induced platelet aggregation not by binding to glycoprotein Ib, because rhodocytin-induced platelet aggregation was not influenced by echicetin, a glycoprotein Ib-binding protein, that completely inhibits platelet agglutination by bovine von Willebrand factor. These findings indicate that rhodocytin is a novel protein structurally related to heterodimers of CRD-like subunits, but functionally distinct from venom proteins that induce platelet aggregation via glycoprotein Ib.
Shin
Y
Y
Department of Biochemistry, Meiji College of Pharmacy, Tokyo, Japan.
Morita
T
T
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002352:Carrier Proteins; D002417:Cattle; D003435:Crotalid Venoms / Q000737:chemistry*; D037102:Lectins / Q000302:isolation & purification / Q000494:pharmacology*; D037181:Lectins, C-Type; D008969:Molecular Sequence Data; D010974:Platelet Aggregation / Q000187:drug effects; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000378:metabolism*; D011506:Proteins / Q000494:pharmacology; D014757:Viper Venoms / Q000494:pharmacology; D014841:von Willebrand Factor / Q000494:pharmacology
D002352:Carrier Proteins; D003435:Crotalid Venoms; D037102:Lectins; D037181:Lectins, C-Type; D019038:Platelet Glycoprotein GPIb-IX Complex; D011506:Proteins; D014757:Viper Venoms; C112292:rhodocytin protein, Calloselasma rhodostoma; D014841:von Willebrand Factor; C080995:echicetin