Structure and orientation of T4 lysozyme bound to the small heat shock protein α-crystallin
Structure and orientation of T4 lysozyme bound to the small heat shock protein α-crystallin
复制标题
DOI：
10.1016/j.jmb.2007.11.014
复制
发表时间：
2008-01-25
影响因子：
5.6
通讯作者：
Mchaourab, Hassane S.
中科院分区：
文献类型：
--
作者：
Claxton, Derek P.;Zou, Ping;Mchaourab, Hassane S.
我们已经确定了结构的变化，伴随着T4溶菌酶（T4 L）和小的热休克蛋白α-晶状体蛋白的不稳定的突变体之间形成一个稳定的复合物。使用对荧光或自旋标记探针指纹的T4 L三级折叠，我们证明，结合破坏三级包装在两个域以及整个活性位点的裂缝。此外，增加的距离之间的i和i+4残基的螺旋支持的模型，其中绑定结构是不是天然的，但显着展开。在寡聚体的范围内，T4 L具有优先取向，其中更疏水的C-末端结构域中的残基被隔离在掩埋的环境中，而N-末端结构域中的残基暴露于水性溶剂。此外，N-末端结构域中的位点的电子顺磁共振谱线形状比折叠的未结合的T4 L中的窄，反映了T4 L和α-晶状体蛋白之间的非结构化骨架和不对称接触模式。净方向不受不稳定突变的位置的影响，这与结合不是由识别局部解折叠触发的概念一致。总之，结构和热力学数据表明，T4 L的稳定结合构象是未折叠的，并支持一个模型，其中两种模式的底物结合起源于两个离散的结合位点上的伴侣。(c)2007爱思唯尔有限公司保留所有权利。
We have determined the structural changes that accompany the formation of a stable complex between a destabilized mutant of T4 lysozyme (T4L) and the small heat shock protein alpha-crystallin. Using pairs of fluorescence or spin label probes to fingerprint the T4L tertiary fold, we demonstrate that binding disrupts tertiary packing in the two domains as well as across the active-site cleft. Furthermore, increased distances between i and i+4 residues of helices support a model in which the bound structure is not native-like but significantly unfolded. In the confines of the oligomer, T4L has a preferential orientation with residues in the more hydrophobic C-terminal domain sequestered in a buried environment, while residues in the N-terminal domain are exposed to the aqueous solvent. Furthermore, electron paramagnetic resonance spectral line shapes of sites in the N-terminal domain are narrower than in the folded, unbound T4L reflecting an unstructured backbone and an asymmetric pattern of contacts between T4L and alpha-crystallin. The net orientation is not affected by the location of the destabilizing mutation consistent with the notion that binding is not triggered by recognition of localized unfolding. Together, the structural and thermodynamic data indicate that the stably bound conformation of T4L is unfolded and support a model in which the two modes of substrate binding originate from two discrete binding sites on the chaperone. (c) 2007 Elsevier Ltd. All rights reserved.