Monodisperse Hsp16.3 nonamer exhibits dynamic dissociation and reassociation, with the nonamer dissociation prerequisite for chaperone-like activity
Monodisperse Hsp16.3 nonamer exhibits dynamic dissociation and reassociation, with the nonamer dissociation prerequisite for chaperone-like activity
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DOI：
10.1016/s0022-2836(02)00311-x
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发表时间：
2002-05-31
影响因子：
5.6
通讯作者：
Chang, ZY
中科院分区：
文献类型：
--
作者：
Gu, LX;Abulimiti, A;Chang, ZY
各种来源的小热休克蛋白（sHsps）通常以低聚物的形式存在，并在体外表现出类似伴侣的活性。Hsp16.3，来自结核分枝杆菌的sHsp，先前被证明在溶液中以单分散的非聚体存在，通过尺寸排除层析和电子低温显微镜分析。本研究是我们了解Hsp16.3的伴侣蛋白机制的一部分，重点研究了该蛋白的寡聚状态的作用。在这里，我们提供的证据表明，Hsp16.3分子在高温下解离，伴随着极大增强的伴侣样活性。此外，当Hsp16.3的非美聚结构被化学交联干扰时，类伴侣活性急剧增加，阻碍了Hsp16.3非美聚体的正确重新结合。这表明非美聚结构的解离是Hsp16.3结合变性底物蛋白的先决条件。另一方面，我们使用放射性标记和非放射性标记蛋白获得的数据清楚地表明，即使在低至4℃的温度下，Hsp16.3低聚物之间也容易发生亚基交换。综上所述，我们认为Hsp16.3虽然在室温下看起来是均匀的，但实际上却发生了快速的动态解离/再结合，并处于平衡状态，从而产生了类似伴侣的活性，主要受环境温度的调节。(C) 2002 Elsevier Science Ltd.版权所有。
Small heat-shock proteins (sHsps) of various origins exist commonly as oligomers and exhibit chaperone-like activities in vitro. Hsp16.3, the sHsp from Mycobacterium tuberculosis, was previously shown to exist as a mono-disperse nonamer in solution when analyzed by size-exclusion chromatography and electron cryomicroscropy. This study represents part of our effort to understand the chaperone mechanism of Hsp16.3, focusing on the role of the oligomeric status of the protein. Here, we present evidence to show that the Hsp16.3 nonamer dissociates at elevated temperatures, accompanied by a greatly enhanced chaperone-like activity. Moreover, the chaperone-like activity was increased dramatically when the nonameric structure of Hsp16.3 was disturbed by chemical cross-linking, which impeded the correct reassociation of Hsp16.3 nonamer. These suggest that the dissociation of the nonameric structure is a prerequisite for Hsp16.3 to bind to denaturing substrate proteins. On the other hand, our data obtained by using radiolabeled and non-radiolabeled proteins clearly demonstrated that subunit exchange occurs readily between the Hsp16.3 oligomers, even at a temperature as low as 4 degreesC. In light of all these observations, we propose that Hsp16.3, although it appears to be homogeneous when examined at room temperature, actually undertakes rapid dynamic dissociation/reassociation, with the equilibrium, and thus the chaperone-like activities, regulated mainly by the environmental temperature. (C) 2002 Elsevier Science Ltd. All rights reserved.