Abstract
Hsp90 populates distinct open and closed conformations mediated by transient N-terminal dimerization. To investigate the mechanistic role of these large conformational changes, we designed Hsp90 with an N-terminal coiled-coil to clamp the termini together and enforce N-domain proximity. Biophysical analyses demonstrate that the coiled-coil effectively maintains N-domain proximity in the absence of ATP, a condition that favors the open state of Hsp90. Enforcing N-domain proximity results in increased ATPase activity, indicating that N-terminal dimerization is a rate-limiting step that is sped-up with the coiled-coil due to increased effective N-domain concentration. The relative difference in ATPase activity between coil-Hsp90 and wt was reduced in the presence of both an ATPase activating (Aha1) and an inhibiting (Sba1) co-chaperone. As both of these co-chaperones bind preferentially to N-terminally dimerized Hsp90, the buffering effect of these co-chaperones demonstrates the biochemical relevance of Hsp90 conformational properties in addition to N-terminal dimerization. Enforcing N-domain proximity is compatible with viability in yeast, underlining the mechanistic relevance of Hsp90 conformational changes that are less dramatic than the transition between fully open and closed.
Highlights
The maturation of clients by Hsp90 requires ATP hydrolysis by the chaperone
These impacts appear to be general as human Hsp90 demonstrated elevated ATPase activity when appended with a coiledcoil
In both yeast and human Hsp90, our results are consistent with N-terminal dimerization being rate-limiting for ATP hydrolysis
Summary
The maturation of clients by Hsp90 requires ATP hydrolysis by the chaperone. Point mutations in Hsp90 that abrogate either ATP binding or hydrolysis both fail to mature hormone receptors and kinases and do not support viability in yeast [7, 8]. These observations have led to a model where ATP binding and hydrolysis triggers a conformational cycle between closed (N-domain dimerized) and open Hsp90 conformations. This observation clearly demonstrates that nucleotide binding impacts the conformation of coilNMC and is consistent with the coiled-coil imposing N-domain proximity distinct from the conformation of the nucleotide-bound closed state.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
