Mechanism of Hemolymph Coagulation System in Invertebrates

鲎前凝血酶和B因子与内毒素敏感性凝血级联反应相关：具有新型“二硫键结结构域“的新型丝氨酸蛋白酶酶原鲎血淋巴对细菌内毒素产生反应并导致快速凝血。该反应由三种丝氨酸蛋白酶酶原（因子C、因子B和前凝血酶）和凝血酶原蛋白（凝血酶原）组成的级联反应组成，所有这些酶在内毒素刺激下通过血细胞脱粒释放。本文描述了凝血酶原和B因子的结构。本研究完成了与该级联反应相关的所有因子的cDNA克隆。凝血酶原是一种单链糖蛋白，分子量为54 kDa。在被因子B激活后，它转化为由L（25 kDa）和H（31 kDa）链组成的双链活性形式凝血酶。用于前凝血酶的cDNA编码包含29个氨基酸的序列， ...更多信息 前原序列的氨基酸残基和成熟蛋白的346个残基。因子B（64 kDa）也是一种糖蛋白，其以单链形式和具有L（25 kDa）和H（40 kDa）链的双链酶原形式存在。因子B酶原被活性因子C激活为B，活性因子C来源于对内毒素敏感的酶原因子C。因子B在成熟形式中具有375个氨基酸残基，此外还有25个信号序列残基。这两种蛋白质的整个氨基酸序列相似，表明这些蛋白质是由基因复制产生的。特别地，丝氨酸蛋白酶结构域在其C-末端的序列同一性计算为43.9%。这两种蛋白质的N-末端区域直到第60个残基具有六个半胱氨酸的相似结构，这在任何其他蛋白质中都没有发现。二硫键的位置上确定的proclotting酶表明，该区域由一个紧凑的“二硫键结域”。与前凝血酶的激活伴随的序列被证明是Arg-Ile键，而因子B，从与其他丝氨酸蛋白酶的序列比对推断，包含独特的-Arg-Gly-Ile-序列。少

Limulus proclotting enzyme and factor b associated with endotoxin-sensitive coagulation cascade : novel serine protease zymogens with a new type of "disulfide-knotted domain"Horseshoe crab (Limulus) hemolymph responds to bacterial endotoxin and results in rapid coagulation. This reaction is composed of a cascade consisting of three serine protease zymogens (factor C, factor B, and proclotting enzyme) and a clottable protein (coagulogen), all of which are released by degranulation of the hemocytes on the stimutation of endotoxin. In the present paper, we describe the structures of proclotting enzyme and factor B. CDNA clonings of all the factors associated with this cascade were completed by this study. Proclotting enzyme is a single-chain glycoprotein with molecular mass of 54 kDa. Upon activation by factor B, it is converted to a two-chain active form clotting enzyme composed of an L (25 kDa) and a H (31 kDa) chains. A CDNA for proclotting enzyme encodes a sequence comprising 29 amino … More acid residues of prepro-sequence and 346 residues of the mature protein. Factor B (64 kDa) is also a glycoprotein that exists as a single-chain form and a two-chain zymogen form with an L (25 kDa) and a H (40 kDa) chains. Factor B zymogen is activated to B by active factor C, which is derived from the zymogen factor C that is sensitive to endotoxin. Factor B has 375 amino acid residues in the mature form, in addition to 25 residues of signal sequence. The entire amino acid sequences of the two proteins are similar, suggeting that these proteins were arisen from a gene duplication. Particularly, the sequence identity of serine protease domains at their C-terminus is calculated to be 43.9%. The N-terminal regions up to 60th residue of both proteins share a similar structure with six cysteines that has not been found in any other proteins. The disulfide locations determined on proclotting enzyme indicate that this region consists of a compact "disulfide-knotted domain". The sequence accompanied with the activation of proclotting enzyme was proven to be an Arg-Ile bond, whereas that of factor B, deduced from sequence alignments with other serine proteases, contained a unique-Arg-Gly-Ile-sequence. Less