近日,，國際著名學(xué)術(shù)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(xì)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(dǎo)型分子伴侶HSP70的C-端螺旋亞結(jié)構(gòu)域在輔伴侶蛋白HSJ1a結(jié)合和激活A(yù)TP酶活性的過程中發(fā)揮著重要作用,，也是首次觀察到J蛋白結(jié)合HSP70后引起C-端螺旋構(gòu)象的變化,。
神經(jīng)特異性表達(dá)的輔伴侶蛋白HSJ1a是輔伴侶蛋白家族的一員,，它同時(shí)具備與分子伴侶HSP70作用并調(diào)節(jié)其ATP酶活性的J結(jié)構(gòu)域和能與泛素結(jié)合的UIM結(jié)構(gòu)域。博士生高雪超等人之前已經(jīng)闡明了HSJ1a可以通過與HSP70作用,，雙重調(diào)節(jié)底物Ataxin-3的降解（PLoS ONE， 6,， e19763,， 2011）。在此基礎(chǔ)上,，高雪超等利用生物化學(xué)和結(jié)構(gòu)生物學(xué)方法,，研究了HSJ1a的J結(jié)構(gòu)域與HSP70結(jié)合并調(diào)節(jié)ATP酶活性的分子機(jī)制。
研究人員首先發(fā)現(xiàn),，HSP70的C-端螺旋對HSP70酶活性的激活非常重要,。隨后，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(jié)果表明,，只有在C-端螺旋完整存在時(shí)，HSJ1a的J結(jié)構(gòu)域才能有效地與HSP70結(jié)合并最大程度地激活HSP70的酶活性,。進(jìn)一步發(fā)現(xiàn),，HSP70的C-端螺旋并不為J結(jié)構(gòu)域提供直接的結(jié)合位點(diǎn)，而是通過影響N-端ATP酶結(jié)構(gòu)域的構(gòu)象來促進(jìn)J結(jié)構(gòu)域與HSP70的相互作用,，而且在J結(jié)構(gòu)域結(jié)合后,，C-端螺旋結(jié)構(gòu)域發(fā)生明顯的構(gòu)象變化。通過解析HSP70的C-端螺旋結(jié)構(gòu)域的結(jié)構(gòu),，研究人員找出了那些發(fā)生變化的殘基位于螺旋與螺旋之間的連接區(qū)域,。
該研究為進(jìn)一步理解HSP70的別構(gòu)調(diào)控機(jī)制提供了新的思路，也為分子伴侶作為疾病干預(yù)靶點(diǎn)的可能性提供了理論依據(jù),。
該項(xiàng)研究工作得到了國家科技部,、基金委、中國科學(xué)院的經(jīng)費(fèi)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.
