title: New insights into the functions and N-glycan structures of factor X activator from Russell's viper venom.
abstract: The coagulation factor X activator from Russell's viper venom (RVV-X) is a heterotrimeric glycoprotein. In this study, its three subunits were cloned and sequenced from the venom gland cDNAs of Daboia siamensis. The deduced heavy chain sequence contained a C-terminal extension with four additional residues to that published previously. Both light chains showed 77-81% identity to those of a homologous factor X activator from Vipera lebetina venom. Far-western analyses revealed that RVV-X could strongly bind protein S, in addition to factors X and IX. This might inactivate protein S and potentiate the disseminated intravascular coagulation syndrome elicited by Russell's viper envenomation. The N-glycans released from each subunit were profiled and sequenced by MALDI-MS and MS/MS analyses of the permethyl derivatives. All the glycans, one on each light chain and four on the heavy chain, showed a heterogeneous pattern, with a combination of variable terminal fucosylation and sialylation on multiantennary complex-type sugars. Amongst the notable features were the presence of terminal Lewis and sialyl-Lewis epitopes, as confirmed by western blotting analyses. As these glyco-epitopes have specific receptors in the vascular system, they possibly contribute to the rapid homing of RVV-X to the vascular system, as supported by the observation that slower and fewer fibrinogen degradation products are released by desialylated RVV-X than by native RVV-X.
authors.affiliation: Graduate Institute of Biochemical Sciences, National Taiwan University, Taiwan.
authors.forename: Hong-Sen
authors.initials: HS
authors.lastname: Chen
authors.forename: Jin-Mei
authors.initials: JM
authors.lastname: Chen
authors.forename: Chia-Wei
authors.initials: CW
authors.lastname: Lin
authors.forename: Kay-Hooi
authors.initials: KH
authors.lastname: Khoo
authors.forename: Inn-Ho
authors.initials: IH
authors.lastname: Tsai
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002236:Carbohydrate Conformation; D017931:DNA Primers; D020536:Enzyme Activators / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D005170:Factor X / Q000378:metabolism*; D006020:Glycopeptides / Q000032:analysis; D006031:Glycosylation; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods; D008969:Molecular Sequence Data; D011134:Polysaccharides / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013379:Substrate Specificity; D014757:Viper Venoms / Q000737:chemistry*
chemical_list: D017931:DNA Primers; D020536:Enzyme Activators; D006020:Glycopeptides; D011134:Polysaccharides; D014757:Viper Venoms; D005170:Factor X