Ito Naoko, Mita Mitsuo, Takahashi Yoshiaki, Matsushima Ayano, Watanabe Yuichi G, Hirano Shigeki, Odani Shoji
Life Science Course, Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan.
Biochem Biophys Res Commun. 2007 Jun 22;358(1):35-40. doi: 10.1016/j.bbrc.2007.04.065. Epub 2007 Apr 19.
Lampreys are one of the most primitive vertebrates diverged some 500 million years ago. It has long been known that parasitic lampreys secrete anticoagulant from their buccal glands and prevent blood coagulation of host fishes. We found two major protein components of 160 and 26 kDa in the buccal gland secretion of parasitic river lamprey, Lethenteron japonicum. The larger protein was identified as river lamprey plasma albumin. The complete primary structure of the 26-kDa protein was determined by protein and cDNA analysis. It belonged to the cysteine-rich secretory protein (CRISP) superfamily that includes recently identified reptile venom ion-channel blockers. Lamprey CRISP blocked depolarization-induced contraction of rat-tail arterial smooth muscle, but showed no effect on caffeine-induced contraction. The result suggests that lamprey CRISP is an L-type Ca(2+)-channel blocker and may act as a vasodilator, which facilitates the parasite to feed on the host's blood. The lamprey CRISP protein contains a number of short insertions throughout the sequence, when aligned with reptilian venom CRISP proteins, probably due to the large evolutionary distance between the Agnatha and the Reptilia, and may represent a novel class of venom CRISP family proteins.
七鳃鳗是约5亿年前分化出来的最原始的脊椎动物之一。长期以来，人们都知道寄生性七鳃鳗会从其颊腺分泌抗凝血剂，从而防止宿主鱼类的血液凝固。我们在寄生性日本七鳃鳗（Lethenteron japonicum）的颊腺分泌物中发现了两种主要的蛋白质成分，分子量分别为160 kDa和26 kDa。较大的蛋白质被鉴定为日本七鳃鳗血浆白蛋白。通过蛋白质和cDNA分析确定了26 kDa蛋白质的完整一级结构。它属于富含半胱氨酸的分泌蛋白（CRISP）超家族，该家族包括最近鉴定出的爬行动物毒液离子通道阻滞剂。七鳃鳗CRISP可阻断大鼠尾动脉平滑肌去极化诱导的收缩，但对咖啡因诱导的收缩没有影响。结果表明，七鳃鳗CRISP是一种L型钙通道阻滞剂，可能起到血管舒张剂的作用，这有助于寄生虫吸食宿主的血液。与爬行动物毒液CRISP蛋白比对时，七鳃鳗CRISP蛋白在整个序列中包含许多短插入片段，这可能是由于无颌类和爬行类之间进化距离较大所致，它可能代表了一类新型的毒液CRISP家族蛋白。
