Excellence Cluster Cardio-Pulmonary System, Center for Molecular Medicine, Vascular Matrix Biology, Frankfurt University Hospital, Frankfurt am Main 60590, Germany.
Biochem J. 2011 Nov 15;440(1):1-11. doi: 10.1042/BJ20110584.
The α2β1 antagonist rhodocetin from Calloselasma rhodostoma is a heterotetrameric CLRP (C-type lectin-related protein) consisting of four distinct chains, α, β, γ and δ. Via their characteristic domain-swapping loops, the individual chains form two subunits, αβ and γδ. To distinguish the four chains which share similar molecular masses and high sequence homologies, we generated 11 mAbs (monoclonal antibodies) with different epitope specificities. Four groups of distinct mAbs were generated: the first targeted the rhodocetin β chain, the second group bound to the αβ subunit mostly in a conformation-dependent manner, the third group recognized the γδ subunit only when separated from the αβ subunit, whereas a fourth group interacted with the γδ subunit both in the heterotetrameric molecule and complexed with the integrin α2 A-domain. Using the specific mAbs, we have shown that the rhodocetin heterotetramer dissociates into the αβ and γδ subunit upon binding to the integrin α2 A-domain at both the molecular and cellular levels. After dissociation, the γδ subunit firmly interacts with the α2β1 integrin, thereby blocking it, whereas the rhodocetin αβ subunit is released from the complex. The small molecular interface between the αβ and γδ subunits within rhodocetin is mostly mediated by charged residues, which causes the two dissociated subunits to have hydrophilic surfaces.
从圆斑蝰蛇（Calloselasma rhodostoma）中分离得到的α2β1 拮抗剂 rhodocetin 是一种四聚体的 CLRP（C 型凝集素相关蛋白），由四个不同的链，α、β、γ和δ组成。通过其特征性的结构域交换环，各个链形成两个亚基，αβ和γδ。为了区分具有相似分子量和高度序列同源性的四条链，我们生成了 11 种具有不同表位特异性的 mAb（单克隆抗体）。生成了四组不同的 mAb：第一组针对 rhodocetin β 链，第二组主要以构象依赖的方式结合αβ 亚基，第三组仅在与αβ 亚基分离时识别γδ 亚基，而第四组与γδ 亚基相互作用在异四聚体分子中和与整合素α2 A 结构域复合时。使用特异性 mAb，我们已经表明，rhodocetin 四聚体在与整合素α2 A 结构域结合时在分子和细胞水平上解离为αβ 和γδ 亚基。解离后，γδ 亚基与α2β1 整合素牢固相互作用，从而阻断它，而 rhodocetin αβ 亚基从复合物中释放。rhodocetin 中αβ 和γδ 亚基之间的小分子界面主要由带电残基介导，这导致两个解离的亚基具有亲水表面。
