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Allosteric opening of the polypeptide-binding site when an Hsp70 binds ATP

2013; Nature Portfolio; Volume: 20; Issue: 7 Linguagem: Inglês

10.1038/nsmb.2583

1545-9993

Ruifeng Qi, Evans Boateng Sarbeng, Qun Liu, Katherine Quynh Le, Xinping Xu, Hongya Xu, Jiao Yang, Jennifer Li Wong, Christina Vorvis, Wayne A. Hendrickson, L. Zhou, Qinglian Liu,

Enzyme Structure and Function

The 70-kDa heat-shock protein 70 (Hsp70) molecular chaperones have a nucleotide binding domain and a substrate binding domain that become allosterically coupled when Hsp70s bind ATP. The crystal structure of the prototypical Hsp70, Escherichia coli DnaK, in an ATP-bound state is now presented. The structure and functional analyses reveal the conformational changes and interdomain interactions that underlie allosteric coupling. The 70-kilodalton (kDa) heat-shock proteins (Hsp70s) are ubiquitous molecular chaperones essential for cellular protein folding and proteostasis. Each Hsp70 has two functional domains: a nucleotide-binding domain (NBD), which binds and hydrolyzes ATP, and a substrate-binding domain (SBD), which binds extended polypeptides. NBD and SBD interact little when in the presence of ADP; however, ATP binding allosterically couples the polypeptide- and ATP-binding sites. ATP binding promotes polypeptide release; polypeptide rebinding stimulates ATP hydrolysis. This allosteric coupling is poorly understood. Here we present the crystal structure of an intact ATP-bound Hsp70 from Escherichia coli at 1.96-Å resolution. The ATP-bound NBD adopts a unique conformation, forming extensive interfaces with an SBD that has changed radically, having its α-helical lid displaced and the polypeptide-binding channel of its β-subdomain restructured. These conformational changes, together with our biochemical assays, provide a structural explanation for allosteric coupling in Hsp70 activity.