STRUCTURE/FUNCTION OF TERMINAL COMPLEMENT PROTEINS

描述（改编自研究者摘要）：长期目的 本项目的目的是详细了解 人补体C5 b-9溶细胞复合物的组装和功能 称为“膜攻击复合物”或MAC。 MAC由C5 b组成 以及端子部件C6、C7、C8和C9。 在后者中，C6，C7， C8-α和C8-β亚基以及C9包含一个独特的 具有高度保守的基因结构、氨基酸序列和 通用模块化设计。 C8-γ亚基是不相关的，是 脂质运载蛋白家族广泛分布的蛋白质， 疏水配体。 由于其在MAC组装中的核心作用， 多亚基结构及其多重相互作用，研究将集中在 主要研究人类C8的结构和功能。 具体目标是： (1)鉴定C8 a中的C8 b和C9结合位点;（2）鉴定C8 a中的片段 介导C8 g的细胞内识别和结合， C8 a-g二聚体的形成;（3）鉴定C5 b-7和C8 a-g结合位点 （4）确定了C8 g的晶体结构并进行了延伸 研究其配体结合特性和功能。 实验将使用 重组（r）形式的人C8 a-g、C8 a、C8 b和C8 g。 结合位点将 使用rC 8a和rC 8b的截短突变体和嵌合体进行鉴定，其中 段系统地交换和分析的产品， 相应的功能交换。 因为它们可能在 在MAC组装过程中介导蛋白质-蛋白质相互作用，研究将 主要集中在每个蛋白质中保守的模块。 其他实验 将尝试结晶C8、C8 a-g、C8 b和rC 8a。 衍射质量 rC 8 g的晶体已经产生，结构将完成。 C8 g的功能及其天然配体的身份尚不清楚。 实验将寻找可能的配体，以及调查 C8 g结合炎症介质的可能性，因此可能抑制 促炎反应 其他实验将研究它在以下方面的作用： 杀菌 对人类C8的拟议研究将提供新的见解 所有终端组件相互作用的机制， 有助于设计和开发治疗上有用的 MAC和MAC裂解和刺激功能的调节剂。 因为MAC 蛋白质家族在结构和功能、信息 这也将有助于理解蛋白质-蛋白质 一般的互动。

DESCRIPTION (Adapted from Investigator's abstract): The long-term objective of this project is to gain a detailed understanding of the mechanism of assembly and function of human C5b-9, the cytolytic complex of complement referred to as the "membrane attack complex" or MAC. MAC is composed of C5b and the terminal components C6, C7, C8 and C9. Among the latter, C6, C7, the C8-alpha and C8-beta subunits, and C9 comprise a unique family of proteins with highly conserved gene structures, amino acid sequences and a common modular design. The C8-gamma subunit is unrelated and is a member of the lipocalin family of widely distributed proteins that bind small hydrophobic ligands. Because of its central role in MAC assembly, its multi-subunit structure and its multiple interactions, studies will focus primarily on the structure and function of human C8. Specific aims are to: (1) identify the C8b and C9 binding sites in C8a; (2) identify the segment of C8a that mediates intracellular recognition and binding of C8g and formation of the C8a-g dimer; (3) identify the C5b-7 and C8a-g binding sites in C8b; (4) determine the crystal structure of C8g and extend ongoing studies of its ligand-binding properties and function. Experiments will use recombinant (r) forms of human C8a-g, C8a, C8b and C8g. Binding sites will be identified using truncated mutants and chimeras of rC8a and rC8b in which segments are systematically exchanged and the products analyzed for a corresponding exchange of function. Because of their likely role in mediating protein-protein interactions during MAC assembly, studies will focus primarily on the modules conserved in each protein. Other experiments will attempt to crystallize C8, C8a-g, C8b and rC8a. Diffraction-quality crystals of rC8g have been produced and the structure will be completed. The function of C8g and identity of its natural ligand are unknown. Experiments will search for possible ligands as well as investigate the possibility that C8g binds inflammatory mediators and thus may inhibit proinflammatory responses. Other experiments will examine its role in bacterial killing. Proposed studies of human C8 will provide new insight into the mechanism by which all the terminal components interact and thereby facilitate the design and development of therapeutically useful analogues of MAC and regulators of MAC lytic and stimulatory functions. Because the MAC family of proteins is unique in terms of structure and function, information obtained will also contribute to an understanding of protein-protein interactions in general.