Binding of the lipocalin C8gamma to human complement protein C8alpha is mediated by loops located at the entrance to the C8gamma ligand binding site.
Binding of the lipocalin C8gamma to human complement protein C8alpha is mediated by loops located at the entrance to the C8gamma ligand binding site.
复制标题
脂质运载蛋白 C8gamma 与人补体蛋白 C8alpha 的结合是由位于 C8gamma 配体结合位点入口处的环介导的。
DOI：
10.1016/j.bbapap.2006.07.003
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
Sodetz,JamesM
中科院分区：
文献类型：
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作者：
Chiswell,Brian;Slade,DanielJ;Sodetz,JamesM
人类C8是五种补体成分(C5b、C6、C7、C8和C9)之一，它们相互作用形成膜攻击复合体(MAC)。C8由二硫键连接的C8α-γ异二聚体和非共价结合的C8β链组成。C8α和C8β与C6、C7和C9同源，而C8γ是补体系统中唯一的Lipocalin。Lipocalin具有核心的β-Barrel结构，形成具有小分子结合位置的花萼。在C8γ中，花萼开口被连接β链的四个环包围。环路1是最大的，包含链接到C8α中的Cys164的Cys40。为了确定这些环是否在C8α的链间二硫键形成之前介导C8α-γ的结合，分别和组合使用这些环来替换铁胆碱(NGAL，LCN2)中的相应环，铁钙蛋白是一种结构上类似于C8γ的脂钙蛋白。铁皮环素-C8γ嵌合构建物在大肠杆菌中表达、纯化并检测其与C8α结合的能力。结果表明，C8γ花萼入口处周围的四个环中至少有三个参与了C8α的结合。靠近花萼入口处的结合表明C8α可能限制并可能调节对C8γ配体结合位点的访问。
Human C8 is one of five complement components (C5b, C6, C7, C8 and C9) that interact to form the membrane attack complex (MAC). C8 is composed of a disulfide-linked C8α-γ heterodimer and a noncovalently associated C8β chain. C8α and C8β are homologous to C6, C7 and C9, whereas C8γ is the only lipocalin in the complement system. Lipocalins have a core β-barrel structure forming a calyx with a binding site for a small molecule. In C8γ, the calyx opening is surrounded by four loops that connect β-strands. Loop 1 is the largest and contains Cys40 that links to Cys164 in C8α. To determine if these loops mediate binding of C8α prior to interchain disulfide bond formation in C8α-γ, the loops were substituted separately and in combination for the corresponding loops in siderocalin (NGAL, Lcn2), a lipocalin that is structurally similar to C8γ. The siderocalin-C8γ chimeric constructs were expressed in E. coli, purified, and assayed for their ability to bind C8α. Results indicate at least three of the four loops surrounding the entrance to the C8γ calyx are involved in binding C8α. Binding near the calyx entrance suggests C8α may restrict and possibly regulate access to the C8γ ligand binding site.