Polgár J, Magnenat E M, Peitsch M C, Wells T N, Saqi M S, Clemetson K J
Theodor Kocher Institute, University of Berne, Freiestrasse 1, CH-3012 Berne, Switzerland.
Biochem J. 1997 Apr 15;323 ( Pt 2)(Pt 2):533-7. doi: 10.1042/bj3230533.
Echicetin, a heterodimeric protein from the venom of Echis carinatus, binds to platelet glycoprotein Ib (GPIb) and so inhibits platelet aggregation or agglutination induced by various platelet agonists acting via GPIb. The amino acid sequence of the beta subunit of echicetin has been reported and found to belong to the recently identified snake venom subclass of the C-type lectin protein family. Echicetin alpha and beta subunits were purified. N-terminal sequence analysis provided direct evidence that the protein purified was echicetin. The paper presents the complete amino acid sequence of the alpha subunit and computer models of the alpha and beta subunits. The sequence of alpha echicetin is highly similar to the alpha and beta chains of various heterodimeric and homodimeric C-type lectins. Neither of the fully reduced and alkylated alpha or beta subunits of echicetin inhibited the platelet agglutination induced by von Willebrand factor-ristocetin or alpha-thrombin. Earlier reports about the inhibitory activity of reduced and alkylated echicetin beta subunit might have been due to partial reduction of the protein.
echicetin是一种来自锯鳞蝰毒液的异源二聚体蛋白，它与血小板糖蛋白Ib（GPIb）结合，从而抑制由各种通过GPIb起作用的血小板激动剂诱导的血小板聚集或凝集。echicetinβ亚基的氨基酸序列已被报道，发现它属于最近鉴定出的C型凝集素蛋白家族的蛇毒亚类。echicetinα亚基和β亚基被纯化。N端序列分析提供了直接证据，证明纯化的蛋白是echicetin。本文给出了α亚基的完整氨基酸序列以及α亚基和β亚基的计算机模型。α-echicetin的序列与各种异源二聚体和同源二聚体C型凝集素的α链和β链高度相似。echicetin的完全还原和烷基化的α亚基或β亚基均未抑制血管性血友病因子-瑞斯托霉素或α-凝血酶诱导的血小板凝集。早期关于还原和烷基化的echicetinβ亚基抑制活性的报道可能是由于该蛋白的部分还原。
