How insulin binds:: the B-Chain α-helix contacts the L1 β-helix of the insulin receptor
How insulin binds:: the B-Chain α-helix contacts the L1 β-helix of the insulin receptor
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DOI：
10.1016/j.jmb.2004.05.023
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发表时间：
2004-08-06
影响因子：
5.6
通讯作者：
Weiss, MA
中科院分区：
文献类型：
--
作者：
Huang, K;Xu, B;Weiss, MA
胰岛素与胰岛素受体的结合在代谢的激素控制中起核心作用。在这里，我们调查可能的接触位点之间的受体和保守的非极性表面的β链。有证据表明，α-螺旋中的两个连续位点，瓦尔（B12）和Tyr（B16）与受体接触。利用化学合成来获得工程化单体（DKP-胰岛素）中的非标准取代。Tyr（B16）被电子等排的可光活化的衍生物（对叠氮基苯丙氨酸）取代使得能够与受体有效交联。这种交联是特异性的，并映射到α亚基的L1 β螺旋。由于较大侧链取代瓦尔（B12）会显著损害受体结合，因此未进行B12的交联研究。相反，通过类似或更小体积的侧链探测结构-功能关系：ValB 12分别被丙氨酸、苏氨酸和α-氨基丁酸取代，导致活性为1（+/-0.1）%、13（+/-6）%和14（+/-5）%（相对于DKP-胰岛素），而没有负协同性的不成比例变化。NMR结构与天然胰岛素基本相同。传输的结构变化的情况下，表明B12类似物的低活性反映了局部扰动的“高亲和力”的电子受体接触。相比之下，因为位置B16耐受丙氨酸取代（相对活性34（10）%），所以该邻近相互作用的贡献较小。总之，我们的研究结果支持了一个模型，其中β链α-螺旋，作为一个重要的识别元件，码头对胰岛素受体的L1 β-螺旋。(C)2004爱思唯尔有限公司保留所有权利。
Binding of insulin to the insulin receptor plays a central role in the hormonal control of metabolism. Here, we investigate possible contact sites between the receptor and the conserved non-polar surface of the beta-chain. Evidence is presented that two contiguous sites in an alpha-helix, Val(B12) and Tyr(B16), contact the receptor. Chemical synthesis is exploited to obtain non-standard substitutions in an engineered monomer (DKP-insulin). Substitution of Tyr(B16) by an isosteric photo-activatable derivative (para-azido-phenylalanine) enables efficient cross-linking to the receptor. Such cross-linking is specific and maps to the L1 beta-helix of the alpha-subunit. Because substitution of Val(B12) by larger side-chains markedly impairs receptor binding, cross-linking studies at B12 were not undertaken. Structure-function relationships are instead probed by side-chains of similar or smaller volume: respective substitution of ValB12 by alanine, threonine, and alpha-aminobutyric acid leads to activities of 1(+/-0.1)%, 13(+/-6)%, and 14(+/-5)% (relative to DKP-insulin) without disproportionate changes in negative cooperativity. NMR structures are essentially identical with native insulin. The absence of transmitted structural changes suggests that the low activities of B12 analogues reflect local perturbation of a "high-affinity" hormone-receptor contact. By contrast, because position B16 tolerates alanine substitution (relative activity 34( 10)%), the contribution of this neighboring interaction is smaller. Together, our results support a model in which the beta-chain alpha-helix, functioning as an essential recognition element, docks against the L1 beta-helix of the insulin receptor. (C) 2004 Elsevier Ltd. All rights reserved.