The high-affinity interaction of human IL-4 and the receptor α chain is constituted by two independent binding clusters
The high-affinity interaction of human IL-4 and the receptor α chain is constituted by two independent binding clusters
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DOI：
10.1006/jmbi.2001.5243
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发表时间：
2002-01-18
影响因子：
5.6
通讯作者：
Sebald, W
中科院分区：
文献类型：
--
作者：
Zhang, JL;Simeonowa, I;Sebald, W
IL 4-BP是IL-4受体α链的胞外结合结构域，含有IL-4的高亲和力结合表位（K-D 150 pM）。先前关于IL-4/IL-4-BP复合物的晶体结构和IL-4的功能表位的结果表明，这种接触包括两个结合簇的镶嵌。本发明的IL-4-BP突变分析支持这一观点，并证明能量上最重要的基团是与簇II中的IL-4 R88形成离子对的D 72的受体羧酸基团。第二个主要受体决定簇是与簇I中的IL-4 E9形成氢键的Y183的羟基。后者与Y 13形成额外的氢键，也与Y 127形成货车范德华接触。受体残基D 72以及Y183各自被来自突变后导致结合亲和力较小降低的残基的疏水基团的壳包围。IL 4 - 13 P双突变体的分析表明，受体侧链在一个集群内，但不是那些不同的集群合作。IL-4和IL-4-BP单突变体的相互作用分析也揭示了簇之间的侧链结合的加和性和每个簇I或II内的协同性。这些结果表明，高亲和力IL-4/IL-4-BP接触由两个独立的结合单元构成，每个单元包含中心极性或带电的侧链，由疏水基团包围（鳄梨簇）。(C)北京大学出版社.
IL4-BP, the extracellular binding domain of the IL-4 receptor alpha chain, contains a high-affinity binding epitope for IL-4 (K-D 150 pM). Previous results on the crystal structure of the IL-4/IL4-BP complex and on the functional epitope of IL-4 suggested that this contact comprises a mosaic of two binding clusters. The present mutational analysis of IL4-BP supports this view and demonstrates that the energetically most important group is the receptor carboxylate group of D72 forming an ion pair with IL-4 R88 in cluster II. The second main receptor determinant is the hydroxyl group of Y183 forming a hydrogen bond with IL-4 E9 in cluster I. The latter is engaged in additional hydrogen bonds with Y13 and also in van der Waals contacts with Y127. Receptor residue D72 as well as Y183 are each surrounded by a shell of hydrophobic groups from residues that upon mutation lead to smaller decreases in binding affinity. Analysis of IL4-13P double mutants showed that receptor side-chains within one cluster but not those of different clusters cooperate. Interaction analysis of IL-4 and IL4-BP single mutants also revealed additivity in binding of side-chains between clusters and cooperativity within each cluster I or II.These results show that the high-affinity IL-4/IL4-BP contact is constituted by two independent binding units, each containing a central polar or charged side-chain surrounded by hydrophobic groups (avocado cluster). (C) 2002 Academic Press.