Maharaj Kevin A, Que Nanette L S, Hong Feng, Huck John D, Gill Sabrina K, Wu Shuang, Li Zihai, Gewirth Daniel T
Hauptman-Woodward Medical Research Institute, Buffalo, New York, United States of America.
Department of Structural Biology, University at Buffalo, Buffalo, New York, United States of America.
PLoS One. 2016 Nov 8;11(11):e0166271. doi: 10.1371/journal.pone.0166271. eCollection 2016.
Grp94 and Hsp90 are the ER and cytoplasmic paralog members, respectively, of the hsp90 family of molecular chaperones. The structural and biochemical differences between Hsp90 and Grp94 that allow each paralog to efficiently chaperone its particular set of clients are poorly understood. The two paralogs exhibit a high degree of sequence similarity, yet also display significant differences in their quaternary conformations and ATPase activity. In order to identify the structural elements that distinguish Grp94 from Hsp90, we characterized the similarities and differences between the two proteins by testing the ability of Hsp90/Grp94 chimeras to functionally substitute for the wild-type chaperones in vivo. We show that the N-terminal domain or the combination of the second lobe of the Middle domain plus the C-terminal domain of Grp94 can functionally substitute for their yeast Hsp90 counterparts but that the equivalent Hsp90 domains cannot functionally replace their counterparts in Grp94. These results also identify the interface between the Middle and C-terminal domains as an important structural unit within the Hsp90 family.
Grp94和Hsp90分别是分子伴侣hsp90家族在内质网和细胞质中的旁系同源成员。Hsp90和Grp94之间的结构和生化差异使得每个旁系同源物能够有效地陪伴其特定的客户蛋白组，但目前人们对此了解甚少。这两个旁系同源物表现出高度的序列相似性，但在四级构象和ATP酶活性方面也存在显著差异。为了确定区分Grp94和Hsp90的结构元件，我们通过测试Hsp90/Grp94嵌合体在体内功能替代野生型伴侣蛋白的能力，来表征这两种蛋白质之间的异同。我们发现，Grp94的N端结构域或中间结构域的第二叶加上C端结构域的组合，可以在功能上替代其酵母Hsp90对应物，但同等的Hsp90结构域不能在功能上取代Grp94中的对应物。这些结果还确定了中间结构域和C端结构域之间的界面是Hsp90家族中的一个重要结构单元。
