3BXQ

The structure of a mutant insulin uncouples receptor binding from protein allostery. An electrostatic block to the TR transition

3BXQ の概要

• エントリーDOI: 10.2210/pdb3bxq/pdb
• 関連するPDBエントリー: 4INS
• 分子名称: insulin A chain, insulin B chain, ZINC ION, ... (4 entities in total)
• 機能のキーワード: tr transition, electrostatic block, protein allostery, receptor binding, hormone
• 細胞内の位置: Secreted: P01308 P01308
• タンパク質・核酸の鎖数: 4
• 化学式量合計: 11804.21

構造登録者

Wan, Z.L.,Huang, K.,Hu, S.Q.,Whittaker, J.,Weiss, M.A. (登録日: 2008-01-14, 公開日: 2008-05-20, 最終更新日: 2024-10-16)

主引用文献

Wan, Z.L.,Huang, K.,Hu, S.Q.,Whittaker, J.,Weiss, M.A.
The structure of a mutant insulin uncouples receptor binding from protein allostery. An electrostatic block to the TR transition.
J.Biol.Chem., 283:21198-21210, 2008

PubMed Abstract: The zinc insulin hexamer undergoes allosteric reorganization among three conformational states, designated T(6), T(3)R(3)(f), and R(6). Although the free monomer in solution (the active species) resembles the classical T-state, an R-like conformational change is proposed to occur upon receptor binding. Here, we distinguish between the conformational requirements of receptor binding and the crystallographic TR transition by design of an active variant refractory to such reorganization. Our strategy exploits the contrasting environments of His(B5) in wild-type structures: on the T(6) surface but within an intersubunit crevice in R-containing hexamers. The TR transition is associated with a marked reduction in His(B5) pK(a), in turn predicting that a positive charge at this site would destabilize the R-specific crevice. Remarkably, substitution of His(B5) (conserved among eutherian mammals) by Arg (occasionally observed among other vertebrates) blocks the TR transition, as probed in solution by optical spectroscopy. Similarly, crystallization of Arg(B5)-insulin in the presence of phenol (ordinarily a potent inducer of the TR transition) yields T(6) hexamers rather than R(6) as obtained in control studies of wild-type insulin. The variant structure, determined at a resolution of 1.3A, closely resembles the wild-type T(6) hexamer. Whereas Arg(B5) is exposed on the protein surface, its side chain participates in a solvent-stabilized network of contacts similar to those involving His(B5) in wild-type T-states. The substantial receptor-binding activity of Arg(B5)-insulin (40% relative to wild type) demonstrates that the function of an insulin monomer can be uncoupled from its allosteric reorganization within zinc-stabilized hexamers.

PubMed: 18492668
DOI: 10.1074/jbc.M800235200

実験手法

X-RAY DIFFRACTION (1.3 Å)