The role of the N-terminal domain of the complement fragment receptor C5L2 in ligand binding.
The role of the N-terminal domain of the complement fragment receptor C5L2 in ligand binding.
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DOI：
10.1074/jbc.m609178200
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发表时间：
2007-02-09
期刊：
影响因子：
--
通讯作者：
Monk PN
中科院分区：
文献类型：
--
作者：
Scola AM;Higginbottom A;Partridge LJ;Reid RC;Woodruff T;Taylor SM;Fairlie DP;Monk PN
C5 L2是一种新的细胞受体，与人过敏毒素补体因子C5 a及其C-末端裂解产物C5 a des Arg相互作用。经典的人C5 a受体（C5 aR）优先结合C5 a，对C5 a des Arg的亲和力低10-100倍。相反，C5 L2以几乎相等的亲和力结合两种配体。C5 aR在其N-末端呈现与C5 a的核心相互作用的酸性和酪氨酸残基，而由跨膜螺旋形成的疏水口袋与C5 a的C-末端中的残基相互作用。在这里，我们研究了C5 L2对C5 a des Arg的亲和力增加的分子基础。大鼠和小鼠C5 L2优先结合C5 a des Arg，而啮齿动物C5 aR对完整C5 a表现出更高的亲和力。C5 aR跨膜疏水口袋的有效肽和非肽配体是配体与C5 L2结合的不良抑制剂。针对人C5 L2的N-末端产生的抗体不影响C5 a与C5 L2的结合，但抑制C5 a des Arg结合。含有C5 aR的N-末端的嵌合C5 L2对C5 a des Arg的亲和力几乎没有影响。在人C5 L2的N-末端中的酸性和酪氨酸残基的突变揭示了三个残基对于C5 a des Arg结合是关键的，但几乎不参与C5 a结合。因此，C5 L2似乎通过不同的机制结合C5 a和C5 a des Arg，并且与C5 aR不同，C5 L2在其N-末端结构域中使用关键残基仅结合C5 a des Arg。
C5L2 is a new cellular receptor found to interact with the human anaphylatoxins complement factor C5a and its C-terminal cleavage product C5a des Arg. The classical human C5a receptor (C5aR) preferentially binds C5a, with a 10-100-fold lower affinity for C5a des Arg. In contrast, C5L2 binds both ligands with nearly equal affinity. C5aR presents acidic and tyrosine residues in its N-terminus that interact with the core of C5a while a hydrophobic pocket formed by the transmembrane helices interacts with residues in the C-terminus of C5a. Here, we have investigated the molecular basis for the increased affinity of C5L2 for C5a des Arg. Rat and mouse C5L2 preferentially bound C5a des Arg, whereas rodent C5aR showed much higher affinity for intact C5a. Effective peptidic and non-peptidic ligands for the transmembrane hydrophobic pocket of C5aR were poor inhibitors of ligand binding to C5L2. An antibody raised against the N-terminus of human C5L2 did not affect the binding of C5a to C5L2 but did inhibit C5a des Arg binding. A chimeric C5L2, containing the N-terminus of C5aR, had little effect on the affinity for C5a des Arg. Mutation of acidic and tyrosine residues in the N-terminus of human C5L2 revealed that three residues were critical for C5a des Arg binding but had little involvement in C5a binding. C5L2 thus appears to bind C5a and C5a des Arg by different mechanisms and, unlike C5aR, C5L2 uses critical residues in its N-terminal domain for binding only to C5a des Arg.