A structural model for GroEL-polypeptide recognition
A structural model for GroEL-polypeptide recognition
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DOI：
10.1073/pnas.94.8.3571
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发表时间：
1997-04-15
影响因子：
11.1
通讯作者：
Fersht, AR
中科院分区：
文献类型：
--
作者：
Buckle, AM;Zahn, R;Fersht, AR
GroEL 的单体肽片段由残基 191-376 组成，是具有功能性伴侣活性的微型伴侣。我们已经以 1.7 埃分辨率解析了带有 17 个残基 N 端标签的 GroEL(191-376) 的晶体结构。一个分子的 N 端标签与晶体中相邻分子的活性位点结合。这似乎模拟了肽底物分子的结合。七个底物残基以相对延伸的构象结合。底物和活性位点之间的相互作用主要是疏水性的，但底物主链和活性位点侧链之间也存在四个氢键。尽管结合底物的优选构象本质上是延伸的，但活性位点的灵活性可以使其适应一般暴露的疏水表面的结合，例如熔球型结构。因此，GroEL 可以通过与疏水区域结合来帮助展开蛋白质，并对完全展开状态施加结合压力，从而充当“解折叠酶”。迷你伴侣的结构与完整 GroEL 中残基 191-376 的结构非常相似，因此我们可以将其构建到 GroEL 中，并重建肽如何与十四聚体结合。注意到连接的结合位点环可以解释底物结合和活性的许多方面。
A monomeric peptide fragment of GroEL, consisting of residues 191-376, is a mini-chaperone with a functional chaperoning activity. We have solved the crystal structure at 1.7 Angstrom resolution of GroEL(191-376) with a 17-residue N-terminal tag. The N-terminal tag of one molecule binds in the active site of a neighboring molecule in the crystal. This appears to mimic the binding of a peptide substrate molecule. Seven substrate residues are bound in a relatively extended conformation. Interactions between the substrate and the active site are predominantly hydrophobic, but there are also four hydrogen bonds between the main chain of the substrate and side chains of the active site. Although the preferred conformation of a bound substrate is essentially extended, the flexibility of the active site may allow it to accommodate the binding of exposed hydrophobic surfaces in general, such as molten globule-type structures. GroEL can therefore help unfold proteins by binding to a hydrophobic region and exert a binding pressure toward the fully unfolded state, thus acting as an ''unfoldase.'' The structure of the mini-chaperone is very similar to that of residues 191-376 in intact GroEL, so we can build it into GroEL and reconstruct how a peptide can bind to the tetradecamer. A ring of connected binding sites is noted that can explain many aspects of substrate binding and activity.