Arpijuntarangkoon Jaradpong, Rojnuckarin Ponlapat, Muanpasitporn Chuanchom, Kaeothip Sophon, Sangvanich Polkit, Intragumtornchai Tanin
Department of Medicine, Chulalongkorn University, Rama IV Road, Patumwan, Bangkok 10330, Thailand.
Platelets. 2007 Jun;18(4):266-72. doi: 10.1080/09537100601078232.
Green pit viper (Trimeresurus albolabris) venom contains a variety of C-type lectin-like proteins (CLPs) causing platelet aggregation and consumptive thrombocytopenia in biting victims. Alboaggregin B (AL-B), a heterodimeric glycoprotein (Gp) Ib-binding protein, was purified from the venom, but there is no reported cDNA sequence and the platelet agglutination mechanism is poorly understood. The full-length AL-B beta clone was obtained from T. albolabris venom gland cDNA library. AL-B alpha was, later, derived using 3'-RACE based on the conserved sequence. In this study, purified AL-B dimer agglutinated human platelets with the EC(50) of 180 nM and was completely inhibited by anti GpIb antibody. MALDI ToF mass spectroscopy found no glycosylation. The peptide mass fingerprints were matched with deduced amino acid sequences of cloned genes. AL-B alpha and beta contained 156 and 146 amino acid, respectively, including 23-residue signal peptides. AL-B beta showed the conserved hydrophilic patches, putative sites for GpIb binding. Furthermore, there was another conserved motif (SRTY) exclusively in platelet-agglutinating AL-B, TSV-GPIb-BP and Mamushigin. We propose that these three CLPs may function as bivalent adhesive proteins linking two GpIb molecules on adjacent platelets.
竹叶青（白唇竹叶青，Trimeresurus albolabris）毒液含有多种C型凝集素样蛋白（CLPs），可导致被咬伤者出现血小板聚集和消耗性血小板减少。从毒液中纯化出了一种异二聚体糖蛋白（Gp）Ib结合蛋白——白唇竹叶青凝集素B（AL - B），但尚无其cDNA序列的报道，且血小板凝集机制也鲜为人知。从白唇竹叶青毒腺cDNA文库中获得了全长AL - Bβ克隆。随后，基于保守序列利用3'-RACE法获得了AL - Bα。在本研究中，纯化的AL - B二聚体使人类血小板发生凝集，其半数有效浓度（EC(50)）为180 nM，且被抗GpIb抗体完全抑制。基质辅助激光解吸电离飞行时间质谱（MALDI ToF）分析未发现糖基化现象。肽质量指纹图谱与克隆基因推导的氨基酸序列相匹配。AL - Bα和β分别包含156和146个氨基酸，包括23个残基的信号肽。AL - Bβ显示出保守的亲水区，这是推测的GpIb结合位点。此外，在能使血小板凝集的AL - B、TSV - GPIb - BP和白眉蝮蛇凝集素中存在另一个保守基序（SRTY）。我们推测这三种CLPs可能作为二价黏附蛋白，连接相邻血小板上的两个GpIb分子发挥作用。
