Xue You-Lin, Zhou Lei, Sun Yuna, Li Hui, Jones Gary W, Song Youtao
School of Environmental Science, Liaoning University, Shenyang, 110036, China.
College of Light Industry, Liaoning University, Shenyang, 110036, China.
J Mol Model. 2017 Oct 23;23(11):320. doi: 10.1007/s00894-017-3453-2.
The Hsp70 and Hsp40 chaperone machine plays critical roles in protein folding, membrane translocation, and protein degradation by binding and releasing protein substrates in a process that utilizes ATP. The activities of the Hsp70 family of chaperones are recruited and stimulated by the J domains of Hsp40 chaperones. However, structural information on the Hsp40-Hsp70 complex is lacking, and the molecular details of this interaction are yet to be elucidated. Here we used steered molecular dynamics (SMD) simulations to investigate the molecular interactions that occur during the dissociation of the auxilin J domain from the Hsc70 nucleotide-binding domain (NBD). The changes in energy observed during the SMD simulation suggest that electrostatic interactions are the dominant type of interaction. Additionally, we found that Hsp70 mainly interacts with auxilin through the surface residues Tyr866, Arg867, and Lys868 of helix II, His874, Asp876, Lys877, Thr879, and Gln881 of the HPD loop, and Phe891, Asn895, Asp896, and Asn903 of helix III. The conservative residues Tyr866, Arg867, Lys868, His874, Asp876, Lys877, and Phe891 were also found in a previous study to be indispensable to the catalytic activity of the DnaJ J domain and the binding of it with the NBD of DnaK. The in silico identification of the importance of auxilin residues Asn895, Asp896, and Asn903 agrees with previous mutagenesis and NMR data suggesting that helix III of the J domain of the T antigen interacts with Hsp70. Furthermore, our data indicate that Thr879 and Gln881 from the HPD loop are also important as they mediate the interaction between the bovine auxilin J domain and Hsc70.
热休克蛋白70（Hsp70）和热休克蛋白40（Hsp40）伴侣机制在蛋白质折叠、膜易位及蛋白质降解过程中发挥着关键作用，该过程通过利用ATP结合并释放蛋白质底物来实现。Hsp40伴侣蛋白的J结构域可募集并刺激Hsp70家族伴侣蛋白的活性。然而，目前尚缺乏关于Hsp40 - Hsp70复合物的结构信息，这种相互作用的分子细节也有待阐明。在此，我们运用引导分子动力学（SMD）模拟来研究辅助蛋白J结构域与热休克同源蛋白70（Hsc70）核苷酸结合结构域（NBD）解离过程中发生的分子相互作用。SMD模拟过程中观察到的能量变化表明，静电相互作用是主要的相互作用类型。此外，我们发现Hsp70主要通过螺旋II的表面残基Tyr866、Arg867和Lys868、HPD环的His874、Asp876、Lys877、Thr879和Gln881以及螺旋III的Phe891、Asn895、Asp896和Asn903与辅助蛋白相互作用。先前的一项研究还发现，保守残基Tyr866、Arg867、Lys868、His874、Asp876、Lys877和Phe891对于DnaJ J结构域的催化活性及其与DnaK的NBD的结合不可或缺。对辅助蛋白残基Asn895、Asp896和Asn903重要性的计算机模拟鉴定结果与先前的诱变和核磁共振数据一致，这些数据表明T抗原J结构域的螺旋III与Hsp70相互作用。此外，我们的数据表明，HPD环中的Thr879和Gln881也很重要，因为它们介导了牛辅助蛋白J结构域与Hsc70之间的相互作用。
