西亚试剂：Structures of GRP94-Nucleotide Complexes Reveal Mechanistic

Structures of GRP94-Nucleotide Complexes Reveal Mechanistic Differences between the hsp90 Chaperones

D. Eric Dollins,1,2 Joshua J. Warren,2 Robert M. Immormino,1,2 and Daniel T. Gewirth1,

1 Hauptman-Woodward Medical Research Institute, 700 Ellicott Street, Buffalo, NY 14203, USA
2 Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA

Corresponding author
Daniel T. Gewirth
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 Å 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.