Osmolyte‐induced conformational changes in the Hsp90 molecular chaperone

Street, Timothy O.; Krukenberg, Kristin A.; Rosgen, JÃ¶rg; Bolen, D. Wayne; Agard, David A.

doi:10.1002/pro.282

Cited by 64 publications

(46 citation statements)

References 39 publications

(59 reference statements)

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“…Previous work demonstrated that osmolytes affect the conformational state of Hsp90, but have little influence on its ATPase activity (33). Work from Auton and Bolen (34) has suggested that the energetic influence of osmolytes originates primarily from the exposure of the peptide backbone.…”

Section: Discussionmentioning

confidence: 99%

Crowding Activates Heat Shock Protein 90

Halpin

Huang

Sun

et al. 2016

Journal of Biological Chemistry

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Hsp90 is a dimeric ATP-dependent chaperone involved in the folding, maturation, and activation of diverse target proteins. Extensive in vitro structural analysis has led to a working model of Hsp90's ATP-driven conformational cycle. An implicit assumption is that dilute experimental conditions do not significantly perturb Hsp90 structure and function. However, Hsp90 undergoes a dramatic open/closed conformational change, which raises the possibility that this assumption may not be valid for this chaperone. Indeed, here we show that the ATPase activity of Hsp90 is highly sensitive to molecular crowding, whereas the ATPase activities of Hsp60 and Hsp70 chaperones are insensitive to crowding conditions. Polymer crowders activate Hsp90 in a non-saturable manner, with increasing efficacy at increasing concentration. Crowders exhibit a non-linear relationship between their radius of gyration and the extent to which they activate Hsp90. This experimental relationship can be qualitatively recapitulated with simple structure-based volume calculations comparing open/closed configurations of Hsp90. Thermodynamic analysis indicates that crowding activation of Hsp90 is entropically driven, which is consistent with a model in which excluded volume provides a driving force that favors the closed active state of Hsp90. Multiple Hsp90 homologs are activated by crowders, with the endoplasmic reticulumspecific Hsp90, Grp94, exhibiting the highest sensitivity. Finally, we find that crowding activation works by a different mechanism than co-chaperone activation and that these mechanisms are independent. We hypothesize that Hsp90 has a higher intrinsic activity in the cell than in vitro.Molecular chaperones play a central role in maintaining folded and active proteins in the cell. Hsp70 class chaperones inhibit misfolding by binding and releasing short hydrophobic segments of unstructured polypeptides with cycles of ATP hydrolysis. Hsp60 class chaperonins promote folding by isolating single protein chains within an isolated cavity. Similar to Hsp70 and Hsp60, Hsp90 has an essential ATPase activity, but the underlying functional mechanism appears to be different. Hsp90 plays important regulatory roles under non-stress conditions by its interactions with specific classes of substrates ("clients") such as kinases and nuclear receptors (1). Hsp90 has a dimeric structure that can undergo dramatic rearrangements upon ATP binding and hydrolysis. Despite significant progress in characterizing Hsp90's ATP-dependent conformational cycle in vitro, it is still unclear how Hsp90 performs its many critical cellular functions.Hsp90 conformational heterogeneity results from rigid-body rearrangements of the three domains within the monomer. The N-terminal domain (site of nucleotide binding) can rotate relative to the middle domain. The middle domain can be positioned against the C-terminal domain (site of dimerization) in multiple orientations, resulting in a flexible and structurally heterogeneous open conformation. Indeed, all full-length Hsp90 str...

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Section: Discussionmentioning

confidence: 99%

Crowding Activates Heat Shock Protein 90

Halpin

Huang

Sun

et al. 2016

Journal of Biological Chemistry

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“…1b). Hsp90 is a highly flexible molecule and adopts distinct conformations during its functional cycle, which is regulated in turn by a variety of cofactors 3,[6][7][8][9] , as is also the case for Hsp70 (ref. 3).…”

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confidence: 89%

Structural characterization of the substrate transfer mechanism in Hsp70/Hsp90 folding machinery mediated by Hop

et al. 2014

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“…Mechanisms other than competition of choline and glycine betaine for the same ligand-binding site come to mind: (i) binding of glycine betaine to an allosteric effector site in GbsR influencing the occupancy of the choline-binding site and (ii) opposing effects of choline and glycine betaine on dimer formation of GbsR. Alternatively, glycine betaine might not bind directly to GbsR at all and might instead exert its regulatory effects indirectly through its "chemical chaperone" function (16,17) that can influence protein folding and conformation (7,8,56). Osmoprotectants other than glycine betaine can tune down choline-mediated GbsR-dependent induction of gbsAB expression.…”

Section: Subtilis (48) and Chox (K D 2 M) From Agrobacterium Tumefmentioning

confidence: 99%