Department of Structural and Molecular Biology, Division of Biosciences, Darwin Building, University College London, Gower Street, London WC1E 6BT, UK.
Biochem Soc Trans. 2010 Aug;38(4):894-900. doi: 10.1042/BST0380894.
Experimental studies of protein-protein interactions are very much affected by whether the complexes are fully formed (strong, with nanomolar dissociation constants) or partially dissociated (weak, with micromolar dissociation constants). The functions of the complement proteins of innate immunity are governed by the weak interactions between the activated proteins and their regulators. Complement is effective in attacking pathogens, but not the human host, and imbalances in this process can lead to disease conditions. The inherent complexity in analysing complement interactions is augmented by the multivalency of its main regulator, CFH (complement factor H), for its physiological or pathophysiological ligands. The unravelling of such weak protein-protein or protein-ligand interactions requires a multidisciplinary approach. Synchrotron X-ray solution scattering and constrained modelling resulted in the determination of the solution structure of CFH and its self-associative properties, whereas AUC (analytical ultracentrifugation) identified the formation of much larger CFH multimers through the addition of metals such as zinc. The ligands of CFH, such as CRP (C-reactive protein), also undergo self-association. The combination of X-rays and AUC with SPR (surface plasmon resonance) proved to be essential to identify CRP self-association and revealed how CFH interacts with CRP. We show that CRP unexpectedly binds to CFH at two non-contiguous sites and explain its relevance to age-related macular degeneration.
蛋白质-蛋白质相互作用的实验研究非常受复合物是否完全形成（强相互作用，具有纳摩尔解离常数）或部分解离（弱相互作用，具有微摩尔解离常数）的影响。先天免疫补体蛋白的功能受激活蛋白与其调节剂之间的弱相互作用控制。补体在攻击病原体方面非常有效，但对人体宿主无效，而该过程的失衡可能导致疾病状况。其主要调节剂 CFH（补体因子 H）与其生理或病理生理配体的多价性增加了分析补体相互作用的内在复杂性。揭示这种弱的蛋白质-蛋白质或蛋白质-配体相互作用需要多学科的方法。同步加速器 X 射线溶液散射和约束建模导致了 CFH 的溶液结构及其自缔合特性的确定，而 AUC（分析超速离心）通过添加锌等金属确定了 CFH 多聚体的形成。CFH 的配体，如 CRP（C 反应蛋白），也会发生自缔合。X 射线和 AUC 与 SPR（表面等离子体共振）的结合被证明对于识别 CRP 自缔合以及揭示 CFH 如何与 CRP 相互作用是必不可少的。我们表明，CRP 出人意料地在两个不连续的位点结合 CFH，并解释其与年龄相关性黄斑变性的相关性。
