title: Functional and sequence characterization of coagulation factor IX/factor X-binding protein from the venom of Echis carinatus leucogaster.
abstract: A new coagulation factor IX/factor X-binding protein (IX/X-bp) from Echis carinatus leucogaster venom has been purified and designated ECLV IX/X-bp. ECLV IX/X-bp binds factor IX and X in a Ca(2+)-dependent manner and is devoid of thrombin-inhibitory and platelet-aggregating activities. The apparent dissociation constants (Kd) for binding of ECLV IX/X-bp to factor IX and factor X are 6.6 and 125 nM, respectively. Upon the addition of Mg2+, the required Ca2+ concentration for optimal binding of ECLV IX/X-bp to factor IX and factor X was prominently reduced. Mg2+ also increases the affinity of factor X for the venom protein. Direct binding of IX/X-bp to factor IX and X could also be detected by far-Western blotting, and results of the experiment ruled out the lectin-like mechanism of ECLV IX/X-bp. The complete amino acid sequence and the disulfide pattern of ECLV IX/X-bp was deduced by enzymatic hydrolysis and automated sequencing of the S-pyridylethylated protein. The venom protein is a heterodimer with one subunit of 131 amino acid residues and another of 125 residues. Both subunits are homologous to each other and to other snake venom proteins of the C-type lectin superfamily.
authors.affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan, Republic of China.
authors.forename: Y L
authors.initials: YL
authors.lastname: Chen
authors.forename: I H
authors.initials: IH
authors.lastname: Tsai
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002417:Cattle; D004220:Disulfides / Q000737:chemistry; D005164:Factor IX / Q000187:drug effects* / Q000378:metabolism; D005170:Factor X / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D037102:Lectins / Q000737:chemistry* / Q000145:classification / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology; D037181:Lectins, C-Type; D008274:Magnesium / Q000494:pharmacology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010974:Platelet Aggregation / Q000187:drug effects; D011485:Protein Binding; D013917:Thrombin / Q000187:drug effects; D014757:Viper Venoms / Q000737:chemistry* / Q000494:pharmacology
chemical_list: D004220:Disulfides; D037102:Lectins; D037181:Lectins, C-Type; D014757:Viper Venoms; C099136:factor IX-factor X-binding protein, Echis carinatus; D005164:Factor IX; D005170:Factor X; D013917:Thrombin; D008274:Magnesium; D002118:Calcium