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Mol Cell. 2007 Oct 12;28(1):41-56.

Structures of GRP94-nucleotide complexes reveal mechanistic differences between the hsp90 chaperones.

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1
Hauptman-Woodward Medical Research Institute, 700 Ellicott Street, Buffalo, NY 14203, USA.

Abstract

GRP94, an essential endoplasmic reticulum chaperone, is required for the conformational maturation of proteins destined for cell-surface display or export. The extent to which GRP94 and its cytosolic paralog, Hsp90, share a common mechanism remains controversial. GRP94 has not been shown conclusively to hydrolyze ATP or bind cochaperones, and both activities, by contrast, result in conformational changes and N-terminal dimerization in Hsp90 that are critical for its function. Here, we report the 2.4 A crystal structure of mammalian GRP94 in complex with AMPPNP and ADP. The chaperone is conformationally insensitive to the identity of the bound nucleotide, adopting a "twisted V" conformation that precludes N-terminal domain dimerization. We also present conclusive evidence that GRP94 possesses ATPase activity. Our observations provide a structural explanation for GRP94's observed rate of ATP hydrolysis and suggest a model for the role of ATP binding and hydrolysis in the GRP94 chaperone cycle.

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PMID:
17936703
PMCID:
PMC2094010
DOI:
10.1016/j.molcel.2007.08.024
[Indexed for MEDLINE]
Free PMC Article

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