Sti1/Hop Plays a Pivotal Role in Hsp90 Regulation Beyond Bridging Hsp70

  • Michael ReidyEmail author
Part of the Heat Shock Proteins book series (HESP, volume 19)


Since its initial characterization, Hop (Hsp90/Hsp70 organizing protein), known as Sti1 in yeast (stress inducible) is mostly understood to serve as a bridge that facilitates transfer of substrate “client” proteins from Hsp70 to Hsp90. Recent work has shown that Sti1 regulates Hsp90 in a manner distinct from its role as a bridge to Hsp70. This second function of Sti1 seems to be to position Hsp90 for subsequent steps of the client maturation cycle, after the client has been transferred from Hsp70. Thus, Sti1/Hop occupies a central gatekeeper role in the Hsp90 reaction cycle, by first facilitating client access to Hsp90 and then promoting the next steps of the cycle.


Chaperone Co-chaperone Hop Hsp Hsp70 Hsp90 Sti1 



Three dimensional


Androgen receptor


Adenosine triphosphate


Cryoelectron microscopy


Aspartate/proline-rich motif


Electron microscopy


5′Fluoro-orotic acid


Glucocorticoid receptor


Hsp90/Hsp70 organizing protein


Heat shock protein


Mitogen-activated protein


Sti1-dependent carboxy-terminal proximal


Sti1-dependent amino-terminal proximal


Tetratricopeptide repeat



We thank our National Institutes of Health colleagues for insightful discussions and help with the manuscript. This work was supported by the Intramural Program of the National Institutes of Health, National Institute of Diabetes and Digestive and Kidney diseases.


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© Springer Nature Switzerland AG 2019

Authors and Affiliations

  1. 1.Laboratory of Biochemistry and GeneticsNational Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of HealthBethesdaUSA

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