Apo-Hsp90 coexists in two open conformational states in solution
Apo-Hsp90 coexists in two open conformational states in solution
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DOI：
10.1042/bc20070149
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发表时间：
2008-07-01
影响因子：
2.7
通讯作者：
Garnier, Cyrille
中科院分区：
文献类型：
--
作者：
Bron, Patrick;Giudice, Emmanuel;Garnier, Cyrille
背景资料。热休克蛋白90（90 kDa heat-shock protein，HSP 90）在许多参与信号转导和细胞周期调控的客户蛋白的折叠和激活中起关键作用。热休克蛋白90的循环与大的构象重排密切相关，这是核苷酸结合依赖性的。然而，到目前为止，我们对Hsp 90构象变化的理解来自于结构信息，这是指重组Hsp 90构建体或原核同源物HtpG（Hsp 90原核同源物）的晶体状态。在这里，我们展示了通过小角X射线散射和单颗粒冷冻EM（冷冻电子显微镜）获得的整个真核Hsp 90（apo-Hsp 90）的第一个无核苷酸结构。我们发现，在解决方案中，载脂蛋白热休克蛋白90是在两个开放的状态，以前从未描述过的构象平衡。通过将我们的cryo-EM图谱与HtpG和已知的Hsp 90结构进行比较，我们确定了在两种Hsp 90 apo-形式之间切换所涉及的结构变化需要两个柔性铰链区周围的NTD（N-末端结构域）和MD（中间结构域）的大移动。本研究显示，第一次，整个真核apo-Hsp 90的结构，沿着其内在的灵活性。虽然大的结构重排，导致部分关闭的热休克蛋白90二聚体，以前归因于核苷酸的结合，我们的研究结果表明，他们实际上主要是由于热休克蛋白90二聚体的内在灵活性。考虑到热休克蛋白90的结构的动态性质的优势作用，我们重新考虑热休克蛋白90 ATP酶循环。
Background information. Hsp90 (90 kDa heat-shock protein) plays a key role in the folding and activation of many client proteins involved in signal transduction and cell cycle control. The cycle of Hsp90 has been intimately associated with large conformational rearrangements, which are nucleotide-binding-dependent. However, up to now, our understanding of Hsp90 conformational changes derives from structural information, which refers to the crystal states of either recombinant Hsp90 constructs or the prokaryotic homologue HtpG (Hsp90 prokaryotic homologue).Results and discussion. Here, we present the first nucleotide-free structures of the entire eukaryotic Hsp90 (apo-Hsp90) obtained by small-angle X-ray scattering and single-particle cryo-EM (cryo-electron microscopy). We show that, in solution, apo-Hsp90 is in a conformational equilibrium between two open states that have never been described previously. By comparing our cryo-EM maps with HtpG and known Hsp90 structures, we establish that the structural changes involved in switching between the two Hsp90 apo-forms require large movements of the NTD (N-terminal domain) and MD (middle domain) around two flexible hinge regions.Conclusions. The present study shows, for the first time, the structure of the entire eukaryotic apo-Hsp90, along with its intrinsic flexibility. Although large structural rearrangements, leading to partial closure of the Hsp90 dimer, were previously attributed to the binding of nucleotides, our results reveal that they are in fact mainly due to the intrinsic flexibility of Hsp90 dimer. Taking into account the preponderant role of the dynamic nature of the structure of Hsp90, we reconsider the Hsp90 ATPase cycle.