Institute of Systems Biomedicine, Department of Biophysics, Beijing Key Laboratory of Tumor Systems Biology and Center for Molecular and Translational Medicine, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, P.R. China; School of Bioscience and Bioengineering, South China University of Technology, Guangzhou 510006, P.R. China; Co-first author.
Institute of Systems Biomedicine, Department of Biophysics, Beijing Key Laboratory of Tumor Systems Biology and Center for Molecular and Translational Medicine, School of Basic Medical Sciences, Peking University Health Science Center, Beijing 100191, P.R. China; Co-first author.
Structure. 2015 Nov 3;23(11):2066-75. doi: 10.1016/j.str.2015.08.015. Epub 2015 Oct 1.
Small heat-shock proteins (sHsps) maintain cellular homeostasis by binding to denatured client proteins to prevent aggregation. Numerous studies indicate that the N-terminal domain (NTD) of sHsps is responsible for binding to client proteins, but the binding mechanism and chaperone activity regulation remain elusive. Here, we report the crystal structures of the wild-type and mutants of an sHsp from Sulfolobus solfataricus representing the inactive and active state of this protein, respectively. All three structures reveal well-defined NTD, but their conformations are remarkably different. The mutant NTDs show disrupted helices presenting a reformed hydrophobic surface compatible with recognizing client proteins. Our functional data show that mutating key hydrophobic residues in this region drastically altered the chaperone activity of this sHsp. These data suggest a new model in which a molecular switch located in NTD facilitates conformational changes for client protein binding.
小分子热休克蛋白（sHsps）通过与变性的客户蛋白结合来维持细胞内稳态，防止聚集。大量研究表明，sHsps 的 N 端结构域（NTD）负责与客户蛋白结合，但结合机制和伴侣活性调节仍不清楚。在这里，我们报告了来自 Sulfolobus solfataricus 的 sHsp 的野生型和突变体的晶体结构，分别代表该蛋白的非活性和活性状态。这三种结构都显示出明确的 NTD，但它们的构象却大不相同。突变体 NTDs 显示出破坏的螺旋，呈现出与识别客户蛋白兼容的重新形成的疏水面。我们的功能数据表明，突变该区域的关键疏水性残基会极大地改变这种 sHsp 的伴侣活性。这些数据表明了一种新的模型，其中位于 NTD 的分子开关促进了构象变化以结合客户蛋白。
