Conformation transitions of the polypeptide-binding pocket support an active substrate release from Hsp70s. Issue 1 (December 2017)

• Record Type: Journal Article
• Authors: Yang, Jiao; Zong, Yinong; Su, Jiayue; Li, Hongtao; Zhu, Huanyu; Columbus, Linda; Zhou, Lei; Liu, Qinglian
• Is Part Of: Nature communications. Volume 8:Issue 1(2017)
• Page Start: 1
• Page End: 13
• Publication Date: 2017-12
• Subjects: Biology -- Periodicals; Physical sciences -- Periodicals; 505
• DOI: 10.1038/s41467-017-01310-z
• Languages: English
• ISSNs: 2041-1723

Abstract

Abstract Cellular protein homeostasis depends on heat shock proteins 70 kDa (Hsp70s), a class of ubiquitous and highly conserved molecular chaperone. Key to the chaperone activity is an ATP-induced allosteric regulation of polypeptide substrate binding and release. To illuminate the molecular mechanism of this allosteric coupling, here we present a novel crystal structure of an intact human BiP, an essential Hsp70 in ER, in an ATP-bound state. Strikingly, the polypeptide-binding pocket is completely closed, seemingly excluding any substrate binding. Our FRET, biochemical and EPR analysis suggests that this fully closed conformation is the major conformation for the ATP-bound state in solution, providing evidence for an active release of bound polypeptide substrates following ATP binding. The Hsp40 co-chaperone converts this fully closed conformation to an open conformation to initiate productive substrate binding. Taken together, this study provided a mechanistic understanding of the dynamic nature of the polypeptide-binding pocket in the Hsp70 chaperone cycle. Hsp70s are highly conserved molecular chaperones that play multiple essential roles in maintaining cellular protein homeostasis. Here, the authors provide structural evidence for active substrate release by Hsp70s upon ATP binding and provide insight into the molecular mechanism of ATP-driven Hsp70 chaperone activity.