Chemistry & Biology
Volume 17, Issue 9, 24 September 2010, Pages 1008-1017
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Article
The Quaternary Organization and Dynamics of the Molecular Chaperone HSP26 Are Thermally Regulated

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Summary

The function of ScHSP26 is thermally controlled: the heat shock that causes the destabilization of target proteins leads to its activation as a molecular chaperone. We investigate the structural and dynamical properties of ScHSP26 oligomers through a combination of multiangle light scattering, fluorescence spectroscopy, NMR spectroscopy, and mass spectrometry. We show that ScHSP26 exists as a heterogeneous oligomeric ensemble at room temperature. At heat-shock temperatures, two shifts in equilibria are observed: toward dissociation and to larger oligomers. We examine the quaternary dynamics of these oligomers by investigating the rate of exchange of subunits between them and find that this not only increases with temperature but proceeds via two separate processes. This is consistent with a conformational change of the oligomers at elevated temperatures which regulates the disassembly rates of this thermally activated protein.

Highlights

► Combining biophysical approaches allows characterization of a molecular chaperone ► ScHSP26 populates a heterogeneous ensemble of oligomers ► Upon thermal activation, ScHSP26 oligomers dissociate and shift to larger species ► Quaternary dynamics of ScHSP26 are underpinned by two separate processes

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These authors contributed equally to this work