The assembly and intermolecular properties of the hsp70-Hop-hsp90 molecular chaperone complex
The assembly and intermolecular properties of the hsp70-Hop-hsp90 molecular chaperone complex
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DOI：
10.1074/jbc.m206566200
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发表时间：
2002-10-11
影响因子：
4.8
通讯作者：
Toft, DO
中科院分区：
文献类型：
--
作者：
Hernández, MP;Sullivan, WP;Toft, DO
真核细胞中多种蛋白质的折叠和构象调控都需要多种分子伴侣的高度协同作用，包括HSP70和HSP90，如类固醇激素受体和许多其他信号转导调节因子。这种名为Hop的蛋白质是HSP70和HSP90的接头蛋白，被认为可以优化它们的功能合作。在这里，我们表征了HSP70-Hop-HSP90复合体的组装，并揭示了导致复合体中蛋白质之间构象变化的相互作用。我们发现HSP40通过增强HSP70与Hop复合体的结合在组装中发挥着不可或缺的作用。这是通过刺激HSP70-ATP转化为HSP70-ADP来实现的，HSP70的构象有利于Hop结合。HSP70-Hop-HSP90复合体是高度动态的，正如以前观察到的HSP90与客户蛋白相互作用一样。然而，HSP90与Hop具有高亲和力(K-d=90 nm)，这种结合不受HSP70的影响。HSP70本身与Hop的亲和力较低(K-d=1.3um)，但在HSP90存在下，这种亲和力增加(K-d=250 nm)。HSP90还将Hop二聚体上的HSP70结合位点的数量从没有HSP90时的两个位点减少到存在时的一个位点。HOP可以抑制HSP90的ATP结合和p23结合活性，但如果HSP70存在于复合体中，这一作用可以逆转。综上所述，我们的结果表明HSP70-Hop-HSP90复合体的组装是选择性的，并影响每个蛋白质的构象状态。
The highly coordinated interactions of several molecular chaperones, including hsp70 and hsp90, are required for the folding and conformational regulation of a variety of proteins in eukaryotic cells, such as steroid hormone receptors and many other signal transduction regulators. The protein called Hop serves as an adaptor protein for hsp70 and hsp90 and is thought to optimize their functional cooperation. Here we characterize the assembly of the hsp70-Hop-hsp90 complex and reveal interactions that cause conformational changes between the proteins in the complex. We found that hsp40 plays an integral role in the assembly by enhancing the binding of hsp70 to the Hop complex. This is accomplished by stimulating the conversion of hsp70-ATP to hsp70-ADP, the hsp70 conformation favored for Hop binding. The hsp70-Hop-hsp90 complex is highly dynamic, as has been observed previously for hsp90 in its interaction with client proteins. Nonetheless, hsp90 binds with high affinity to Hop (K-d = 90 nm), and this binding is not affected by hsp70. hsp70 binds with lower affinity to Hop (K-d = 1.3 muM) on its own, but this affinity is increased (K-d = 250 nm) in the presence of hsp90. hsp90 also reduces the number of hsp70 binding sites on the Hop dimer from two sites in the absence of hsp90 to one site in its presence. Hop can inhibit the ATP binding and p23 binding activity of hsp90, yet this can be reversed if hsp70 is present in the complex. Taken together, our results suggest that the assembly of hsp70-Hop-hsp90 complexes is selective and influences the conformational state of each protein.