Tag Archives: chaperone

The endoplasmic reticulum chaperone BiP is a closure-accelerating cochaperone of Grp94

From the article: “The endoplasmic reticulum (ER) is the site at which secreted proteins (such as the hormone insulin) and membrane-bound proteins are folded. ATP-dependent chaperones within the ER help proteins fold. This study describes how two key ER chaperones, BiP and Grp94, work together at a molecular level. BiP binds to Grp94, which enables Grp94 to change conformation and hydrolyze ATP. In short, BiP provides a signal to switch on Grp94 conformational changes that are required to help other proteins fold. This finding helps explain how two chaperones can work together collaboratively in protein folding. Because BiP and Grp94 are members of highly conserved chaperone families, these findings may provide insight into chaperone-assisted protein folding beyond the ER.”  This project was a collaboration with members of Timothy Street‘s lab in the Brandeis Biochemistry Department.

10.1073/pnas.2118793119
Huang B., et al., The endoplasmic reticulum chaperone BiP is a closure-accelerating cochaperone of Grp94.
PNAS 119, e2118793119 (2022)

Conformational Cycling within the Closed State of Grp94, an Hsp90-Family Chaperone

Grp94 is a molecular chaperone that helps to fold and maintain the folded state of “client” proteins in the endoplasmic reticulum.  Acceleration of client folding is driven by conformational changes in Grp94.  However,  the sequence of conformational changes and how these changes are coupled to the cycle of ATP hydrolysis is not well understood.  Prof. Timothy Street and his lab members Bin Huang and Ming Sun, in collaboration with Larry Friedman, did single-molecule fluorescence resonance energy transfer (FRET) experiments to directly observe conformational cycling in individual Grp94 molecules.  Their studies show that ATP hydrolysis can drive repeated cycling between alternative “closed” states of Grp94, suggesting a way that enzyme might propagate structural changes to client molecules. Chemical scheme for conformational cycling of Grp94.

10.1016/j.jmb.2019.06.004
Conformational Cycling within the Closed State of Grp94, an Hsp90-Family Chaperone
Huang, B., Friedman, L.J., Gelles, J., Sun, M., and Street, T.O.
Journal of Molecular Biology 431, 3312-3323 (2019).