Toward the active conformation of insulin - Stereospecific modulation of a structural switch in the B chain
Toward the active conformation of insulin - Stereospecific modulation of a structural switch in the B chain
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DOI：
10.1074/jbc.m602691200
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发表时间：
2006-08-25
影响因子：
4.8
通讯作者：
Weiss, Michael A.
中科院分区：
文献类型：
--
作者：
Hua, Qing-xin;Nakagawa, Satoe;Weiss, Michael A.
胰岛素如何与胰岛素受体结合长期以来一直是人们猜测的话题。尽管游离激素的结构已被广泛表征，但各种证据表明，受体结合时会发生构象变化。在这里，我们采用手性诱变，比较相应的 D 和 L 氨基酸取代，以研究 B 链中可能的转换。为了研究结构、功能和稳定性的相互关系，合成了异构类似物，其中 β 转角中的不变甘氨酸 (Gly(B8)) 被 D- 或 L-Ser 取代。 D 取代增强了稳定性（Delta Delta G(u) 0.9 kcal/mol），但会损害受体结合 100 倍；相比之下，L 取代会显着损害稳定性（Delta Delta G(u) - 3.0 kcal/mol），而受体结合仅减少 2 倍。尽管每个异构体结构都保留了类似天然的整体折叠，但 L-Ser(B8) 类似物比 D-Ser(B8) 类似物或天然单体表现出更少的螺旋相关和长程核奥弗豪瑟效应。不稳定类似物的构象波动增强的证据是由其衰减的圆二色光谱提供的。立体特异性稳定性与受体结合之间的反比关系强烈表明 B7-B10 β 转角改变了受体结合的构象。
How insulin binds to the insulin receptor has long been a subject of speculation. Although the structure of the free hormone has been extensively characterized, a variety of evidence suggests that a conformational change occurs upon receptor binding. Here, we employ chiral mutagenesis, comparison of corresponding D and L amino acid substitutions, to investigate a possible switch in the B-chain. To investigate the interrelation of structure, function, and stability, isomeric analogs have been synthesized in which an invariant glycine in a beta-turn (Gly(B8)) is replaced by D- or L- Ser. The D substitution enhances stability (Delta Delta G(u) 0.9 kcal/mol) but impairs receptor binding by 100-fold; by contrast, the L substitution markedly impairs stability (Delta Delta G(u) - 3.0 kcal/mol) with only 2-fold reduction in receptor binding. Although the isomeric structures each retain a native-like overall fold, the L-Ser(B8) analog exhibits fewer helix-related and long range nuclear Overhauser effects than does the D-Ser(B8) analog or native monomer. Evidence for enhanced conformational fluctuations in the unstable analog is provided by its attenuated CD spectrum. The inverse relationship between stereospecific stabilization and receptor binding strongly suggests that the B7-B10 beta-turn changes conformation on receptor binding.