近日，國際著名學術期刊The Journal of Biological Chemistry（JBC）在線刊登了中科院上海生科院生化與細胞所胡紅雨課題組的研究成果「The C-terminal Helices of Heat Shock Protein 70 Are Essential for J-domain Binding and ATPase Activation」。該論文闡明了人源誘導型分子伴侶HSP70的C-端螺旋亞結構域在輔伴侶蛋白HSJ1a結合和激活ATP酶活性的過程中發揮著重要作用，也是首次觀察到J蛋白結合HSP70後引起C-端螺旋構象的變化。
神經特異性表達的輔伴侶蛋白HSJ1a是輔伴侶蛋白家族的一員，它同時具備與分子伴侶HSP70作用並調節其ATP酶活性的J結構域和能與泛素結合的UIM結構域。博士生高雪超等人之前已經闡明了HSJ1a可以通過與HSP70作用，雙重調節底物Ataxin-3的降解（PLoS ONE， 6， e19763， 2011）。在此基礎上，高雪超等利用生物化學和結構生物學方法，研究了HSJ1a的J結構域與HSP70結合併調節ATP酶活性的分子機制。
研究人員首先發現，HSP70的C-端螺旋對HSP70酶活性的激活非常重要。隨後，他們利用HSJ1a與不同HSP70蛋白片段相互作用的差別，來解釋酶活性激活程度的差異性。結果表明，只有在C-端螺旋完整存在時，HSJ1a的J結構域才能有效地與HSP70結合併最大程度地激活HSP70的酶活性。進一步發現，HSP70的C-端螺旋並不為J結構域提供直接的結合位點，而是通過影響N-端ATP酶結構域的構象來促進J結構域與HSP70的相互作用，而且在J結構域結合後，C-端螺旋結構域發生明顯的構象變化。通過解析HSP70的C-端螺旋結構域的結構，研究人員找出了那些發生變化的殘基位於螺旋與螺旋之間的連接區域。
該研究為進一步理解HSP70的別構調控機制提供了新的思路，也為分子伴侶作為疾病幹預靶點的可能性提供了理論依據。
該項研究工作得到了國家科技部、基金委、中國科學院的經費支持。
（生物谷Bioon.com）
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.