Studies on the mechanism of activation of a protease in the complement system, C3 convertase.

研究补体系统中蛋白酶 C3 转化酶的激活机制。

• 批准号: 60580121
• 负责人: NAGASAWA SHIGEHARU
• 金额: $ 1.6万
• 依托单位: Hokkaido University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1985
• 资助国家: 日本
• 起止时间: 1985 至 1986
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-60580121/
• 关键词: Complement system; Host defense system; Immunology; Protease; C3 convertase; 活性化機構

Complement system is a humoral host defense system composed of multiple protease reactions and C3 convertase is a key enzyme in the complement system. It is assembled from two components, C4b and C2a, which are the activation products of C4 and C2. In this project, we have focused on the functional domains of C4b which are implicated in the molecular assembly of C3 convertase and obtained following results.1) A model of inter-chain disulfide bonds of C4 which is composed of three polypeptide chains ( <alpha> , <beta> , <gamma> ). There is a single S-S bond between <alpha> and <beta> chains, while two S-S bonds are linking between the <alpha> and <gamma> chains. 2) By mild reduction of C4b, two different binding sites for C2a (C-terminal side of C2) and C2b (N-terminal side of C2) were found. The site for C2b is located on the <alpha> - <beta> chains, whereas that for C2a is lost upon the mild reduction.3) Three functionally different monoclonal antibodies (MAb) against C4b were obtained. Using these MAb, it was found that a novel functional site is present on the <beta> chain which labilizes the binding of C2a to C4b.4) Binding of C2b to C3 convertase occurs and results in the dissociation of C3 convertase, suggesting that C2b may play as a regulator for C3 convertase.

补体系统是一个由多种蛋白酶反应组成的体液免疫防御系统，C3转化酶是补体系统中的关键酶。它由两种组分C4 b和C2 a组装而成，它们是C4和C2的活化产物。本课题主要研究了C3转化酶分子组装过程中C4 b的功能结构域，得到以下结果：1）C4的链间二硫键模型，该模型由三条多肽链（<alpha>，<beta>，<gamma>）组成。分子链之间只有一个S-S键<alpha><beta>，分子链之间有两个S-S键连接<alpha><gamma>。2)通过对C4 b的轻度还原，发现C2 a（C2的C端）和C2b（C2的N端）有两个不同的结合位点，其中C2b的结合位点位于<alpha>α<beta>链上，而C2 a的结合位点在轻度还原时丢失。4<beta>）C2b与C3转化酶发生结合并导致C3转化酶解离，提示C2b可能对C3转化酶起调节作用。

项目成果

Chikako Ichihara: Molecular Immunology. 23. 151-157 (1986)

市原知花子：分子免疫学。

Tsukasa Seya: "Location of the interchain disulfide bonds of the fourth component of human complement (C4): Evidence based on the liberation of fragments secondary to thiol-disulfide interchange reactions." The Journal of Immunology. 136. 4152-4156 (1986)

Tsukasa Seya：“人类补体第四个成分 (C4) 的链间二硫键的位置：基于硫醇-二硫键交换反应继发片段释放的证据。”

Mina Yamazaki: "Decay-acceleration of C3 convertase by C2b" J. Immunol.

Mina Yamazaki：“C2b 对 C3 转化酶的衰变加速”J.Immunol。

Mina Yamazaki: FEBS letters. 208. 147-150 (1986)

山崎米娜：FEBS 信件。

Mina Yamazaki: The Journal of Immunology(投稿中).

Mina Yamazaki：免疫学杂志（目前已提交）。