Hsc70-Auxilin复合物的拉伸分子动力学模拟

Hsc70与auxilin蛋白组成的系统是Hsp70/Hsp40分子伴侣系统家族的一员,在热休克反应中发挥重要作用。本文为得出auxilin蛋白J结构域的关键氨基酸,首先采用由二硫键交联的Hsc70 R171C与auxilin D876C的复合物结晶结构作为初始模型,进行分子动力学模拟,通过比较平衡后的结合部位发现,将形成二硫键的氨基酸突变为原来的氨基酸结构在结合位点上与生化结果较为相近,之后利用此结构通过拉伸动力学模拟分析了auxilin蛋白J结构域与Hsc70的ATPase功能域的解离过程,并探讨了Hsc70与auxilin蛋白之间的相互作用力。结果表明位于HPD loop上的His874,Asp876,Thr879,螺旋Ⅲ上的Glu884,Asn895,Asp896,Ser899,Glu902,Asn903为关键氨基酸,这些数据符合之前核磁共振实验证实的T抗原J结构域的HPD基序和螺旋Ⅲ与Hsc70的ATPase功能域之间的相互作用。

Steered molecular dynamics simulations of Hsc70-Auxilin interactions

The Hsc70 and auxilin complex belongs to the Hsp70 and Hsp40 family, a chaperone system bestknown for its role in the heat shock response. The model of the Hsc70/auxilin complex molecule used in our studyhad the crystal structure of disulfide-bond-crosslinked complex of bovine Hsc70 R171C and bovine auxilinD876C. In order to confirm the important residues, we first analyzed the stable model after the moleculardynamics simulation（MD）. The binding site of the mutated（original） model was more aligned with previousbiochemical results. After that, steered molecular dynamics simulations（SMD） were applied to this stable modelto investigate the dissociation of the bovine auxilin J-domain and the Hsc70 ATPase domain, and theHsc70-auxilin interactions were also investigated. Our data indicated that His874, Asp876, and Thr879 from theHPD loop, Glu884, Asn895, Asp896, Ser899, Glu902 and Asn903 from helix Ⅲ are important residues.These data agreed with a previous NMR evidence that helix Ⅲ and HPD motif of large T antigen J-domaininteracted with Hsc70 ATPase domain.