Molecular cloning and characterization of a platelet glycoprotein Ib-binding protein from the venom of Trimeresurus stejnegeri.
A platelet glycoprotein Ib-binding protein, termed TSV-GPIb-BP, was isolated from the venom of Trimeresurus stejnegeri. On SDS-polyacrylamide gel electrophoresis, TSV-GPIb-BP showed a single band with an apparent molecular weight of 28,000 and two distinct bands with apparent molecular weights of 16,000 and 15,000 under non-reducing and reducing conditions, respectively. cDNA clones containing the coding sequences for both TSV-GPIb-BP subunits were isolated and sequenced. The deduced amino acid sequences of TSV-GPIb-BP subunits were confirmed by N-terminal protein sequencing and trypsin-digested peptide mass fingerprinting. Interestingly, the alpha subunit of TSV-GPIb-BP is identical to that of alboaggregin-B, and the sequence identity of their beta subunits is 94.3%. TSV-GPIb-BP inhibited ristocetin-induced human platelet agglutination in platelet-rich plasma under lower dosages (<5 microg/ml). On the other hand, it directly aggregated washed human platelets in the absence of additional Ca2+ or any other cofactors under higher dosages (>5 microg/ml). This platelet aggregation activity was dose-dependently inhibited by specific GPIbalpha antibodies, but not by those antibodies against platelet GPIa, GPIIa, GPIIb and GPIIIa.
Lee
Wen-Hui
WH
Department of Animal Toxinology, Kunming Institute of Zoology, The Chinese Academy of Sciences, 32 East Jiao Chang Road, Kunming, Yunnan 650223, People's Republic of China.
Zhang
Yun
Y
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D003435:Crotalid Venoms / Q000737:chemistry / Q000235:genetics* / Q000494:pharmacology*; D018076:DNA, Complementary / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D015723:Gene Library; D006801:Humans; D008969:Molecular Sequence Data; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000037:antagonists & inhibitors*; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000378:metabolism; D012310:Ristocetin; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D017841:Trimeresurus
D003435:Crotalid Venoms; D018076:DNA, Complementary; D010975:Platelet Aggregation Inhibitors; D019038:Platelet Glycoprotein GPIb-IX Complex; D011956:Receptors, Cell Surface; C029748:Trimeresurus venoms; D012310:Ristocetin