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J Biol Chem. 2011 Apr 1;286(13):11091-8. doi: 10.1074/jbc.M111.223131. Epub 2011 Jan 28.

Enforced N-domain proximity stimulates Hsp90 ATPase activity and is compatible with function in vivo.

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Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.


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.

[Indexed for MEDLINE]
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