Multiple domains of MASP-2, an initiating complement protease, are required for interaction with its substrate C4
Multiple domains of MASP-2, an initiating complement protease, are required for interaction with its substrate C4
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DOI：
10.1016/j.molimm.2011.10.006
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发表时间：
2012-01-01
影响因子：
3.6
通讯作者：
Pike, Robert N.
中科院分区：
文献类型：
--
作者：
Duncan, Renee C.;Bergstrom, Frida;Pike, Robert N.
补体系统是先天性免疫和适应性免疫的基础，可以通过经典途径、凝集素途径或替代途径启动。 MASP-2（凝集素途径的起始蛋白酶）对 C4 的裂解是激活该途径的关键事件，先于病原体表面最终形成 C3 转化酶 (C4bC2a) 复合物。 MASP-2 切割 C4 所需的相互作用可能是通过 C4 与蛋白酶上的外部位点的初始结合来促进的。我们已经证明，具有蛋白水解活性和催化失活的 CCP1-CCP2-丝氨酸蛋白酶 (CCP1-CCP2-SP) 形式均以相似的亲和力结合 C4。有趣的是，含有 CCP1-CCP2 结构域或单独 SP 结构域的蛋白质与 C4 的结合亲和力比 CCP1-CCP2-SP 蛋白质低得多，表明 CCP 结构域与活性位点积极配合，介导 C4 的有效结合和裂解。此外，CCP1 结构域中残基 K342 突变为丙氨酸，消除了与 CCP1-CCP2 形式的 C4 和 C4b 的结合，表明该氨基酸具有关键的静电作用。所提供的数据表明，为了介导与 C4 的高亲和力相互作用，需要所有结构域。 (C) 2011 Elsevier Ltd. 保留所有权利。
The complement system is fundamental to both innate and adaptive immunity and can be initiated via the classical, lectin or alternative pathways. Cleavage of C4 by MASP-2, the initiating protease of the lectin pathway, is a crucial event in the activation of this pathway, preceding the eventual formation of the C3 convertase (C4bC2a) complex on the pathogen surface. Interactions required for the cleavage of C4 by MASP-2 are likely to be facilitated by the initial binding of C4 to an exosite on the protease. We have shown that both proteolytically active and catalytically inactive CCP1-CCP2-serine protease (CCP1-CCP2-SP) forms bind C4 with similar affinity. Interestingly, proteins containing the CCP1-CCP2 domains or the SP domain alone bound C4 with much lower affinity than the CCP1-CCP2-SP protein, suggesting that the CCP domains cooperate positively with the active site to mediate efficient binding and cleavage of C4. In addition, mutation of residue K342 to alanine in the CCP1 domain abolished binding to both C4 and C4b in its CCP1-CCP2 form, suggesting a key electrostatic role for this amino acid. The presented data indicates that all of the domains are required in order to mediate high affinity interaction with C4. (C) 2011 Elsevier Ltd. All rights reserved.