近日，国际著名学术期刊The Journal of Biological Chemistry（JBC）在线刊登了中科院上海生科院生化与细胞所胡红雨课题组的研究成果“The C-terminal Helices of Heat Shock Protein 70 Are Essential for J-domain Binding and ATPase Activation”。该论文阐明了人源诱导型分子伴侣HSP70的C-端螺旋亚结构域在辅伴侣蛋白HSJ1a结合和激活ATP酶活性的过程中发挥着重要作用，也是首次观察到J蛋白结合HSP70后引起C-端螺旋构象的变化。
神经特异性表达的辅伴侣蛋白HSJ1a是辅伴侣蛋白家族的一员，它同时具备与分子伴侣HSP70作用并调节其ATP酶活性的J结构域和能与泛素结合的UIM结构域。博士生高雪超等人之前已经阐明了HSJ1a可以通过与HSP70作用，双重调节底物Ataxin-3的降解（PLoS ONE， 6， e19763， 2011）。在此基础上，高雪超等利用生物化学和结构生物学方法，研究了HSJ1a的J结构域与HSP70结合并调节ATP酶活性的分子机制。
研究人员首先发现，HSP70的C-端螺旋对HSP70酶活性的激活非常重要。随后，他们利用HSJ1a与不同HSP70蛋白片段相互作用的差别，来解释酶活性激活程度的差异性。结果表明，只有在C-端螺旋完整存在时，HSJ1a的J结构域才能有效地与HSP70结合并最大程度地激活HSP70的酶活性。进一步发现，HSP70的C-端螺旋并不为J结构域提供直接的结合位点，而是通过影响N-端ATP酶结构域的构象来促进J结构域与HSP70的相互作用，而且在J结构域结合后，C-端螺旋结构域发生明显的构象变化。通过解析HSP70的C-端螺旋结构域的结构，研究人员找出了那些发生变化的残基位于螺旋与螺旋之间的连接区域。
该研究为进一步理解HSP70的别构调控机制提供了新的思路，也为分子伴侣作为疾病干预靶点的可能性提供了理论依据。
该项研究工作得到了国家科技部、基金委、中国科学院的经费支持。
（生物谷Bioon.com）
doi:10.1074/jbc.M111.294728
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The C-terminal Helices of Heat Shock Protein 70 Are Essential for J-domain Binding and ATPase Activation*
Xue-Chao Gao‡, Chen-Jie Zhou‡, Zi-Ren Zhou‡, Meng Wu‡, Chun-Yang Cao§ and Hong-Yu Hu‡,1
The J-domain co-chaperones work together with the heat shock protein 70 (HSP70) chaperone to regulate many cellular events, but the mechanism underlying the J-domain-mediated HSP70 function remains elusive. We studied the interaction between human-inducible HSP70 and Homo sapiens J-domain protein (HSJ1a), a J domain and UIM motif-containing co-chaperone. The J domain of HSJ1a shares a conserved structure with other J domains from both eukaryotic and prokaryotic species, and it mediates the interaction with and the ATPase cycle of HSP70. Our in vitro study corroborates that the N terminus of HSP70 including the ATPase domain and the substrate-binding β-subdomain is not sufficient to bind with the J domain of HSJ1a. The C-terminal helical α-subdomain of HSP70, which was considered to function as a lid of the substrate-binding domain, is crucial for binding with the J domain of HSJ1a and stimulating the ATPase activity of HSP70. These fluctuating helices are likely to contribute to a proper conformation of HSP70 for J-domain binding other than directly bind with the J domain. Our findings provide an alternative mechanism of allosteric activation for functional regulation of HSP70 by its J-domain co-chaperones.
