The Hsp70 interdomain linker is a dynamic switch that enables allosteric communication between two structured domains
The Hsp70 interdomain linker is a dynamic switch that enables allosteric communication between two structured domains
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DOI：
10.1074/jbc.m117.789313
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发表时间：
2017-09-08
影响因子：
4.8
通讯作者：
Gierasch, Lila M.
中科院分区：
文献类型：
--
作者：
English, Charles A.;Sherman, Woody;Gierasch, Lila M.
热休克蛋白70分子伴侣通过结合不完全折叠或聚集蛋白的暴露疏水区域在细胞蛋白质稳态中起关键作用。Hsp 70的这一关键功能依赖于两个结构良好的结构域之间的变构通讯：N末端核苷酸结合结构域（NBD）和C末端底物结合结构域（SBD），它们通过结构域间接头连接。ATP或ADP与NBD的结合改变了SBD的底物结合亲和力，触发了底物结合和释放的功能性必需循环。结构域间连接体是ATP结合的Hsp 70中结构域间界面的结构良好的参与者。相比之下，在ADP结合状态下，例如大肠杆菌Hsp 70 DnaK，结构域间接头是柔性的。热休克蛋白70域间连接序列是高度保守的，而且，在这一地区的突变妥协域间变构。为了更好地理解该区域在Hsp 70变构中的作用，我们使用分子动力学模拟来探索ADP结合的DnaK中结构域间连接体的构象景观，并通过战略实验数据支持我们的模拟。我们发现，虽然域间连接器样品许多构象，它的行为作为三个相对有序的铰链连接的片段。因此，NBD和SBD之间的距离和取向受到限制。此外，接头的C-末端区域与SBD形成先前未报道的瞬时相互作用，并且主要接头对接位点仅在一种变构状态下可用，即对底物具有高亲和力。这种优先结合暗示了结构域间接头作为动态变构开关。SBD上的接头结合位点是Hsp 70变构循环的小分子调节剂的潜在靶标。
Hsp70 molecular chaperones play key roles in cellular protein homeostasis by binding to exposed hydrophobic regions of incompletely folded or aggregated proteins. This crucial Hsp70 function relies on allosteric communication between two well-structured domains: an N-terminal nucleotide-binding domain (NBD) and a C-terminal substrate-binding domain (SBD), which are tethered by an interdomain linker. ATP or ADP binding to the NBD alters the substrate-binding affinity of the SBD, triggering functionally essential cycles of substrate binding and release. The interdomain linker is a well-structured participant in the interdomain interface in ATP-bound Hsp70s. By contrast, in the ADP-bound state, exemplified by the Escherichia coli Hsp70 DnaK, the interdomain linker is flexible. Hsp70 interdomain linker sequences are highly conserved; moreover, mutations in this region compromise interdomain allostery. To better understand the role of this region in Hsp70 allostery, we used molecular dynamics simulations to explore the conformational landscape of the interdomain linker in ADP-bound DnaK and supported our simulations by strategic experimental data. We found that while the interdomain linker samples many conformations, it behaves as three relatively ordered segments connected by hinges. As a consequence, the distances and orientations between the NBD and SBD are limited. Additionally, the C-terminal region of the linker forms previously unreported, transient interactions with the SBD, and the predominant linker-docking site is available in only one allosteric state, that with high affinity for substrate. This preferential binding implicates the interdomain linker as a dynamic allosteric switch. The linker-binding site on the SBD is a potential target for small molecule modulators of the Hsp70 allosteric cycle.