The molecular chaperone Hsc70 from a eurythermal marine goby exhibits temperature insensitivity during luciferase refolding assays

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The role and function of molecular chaperones has been widely studied in model systems (e.g. yeast, Escherichia coli and cultured mammalian cells), however, comparatively little is known about the function of molecular chaperones in eurythermal ectotherms. To investigate the thermal sensitivity of molecular chaperone function in non-model ectotherms, we examined the in vitro activity of Hsc70, a constitutively expressed member of the 70-kDa heat-shock protein gene family, purified from white muscle of the eurythermal marine goby Gillichthys mirabilis. The activity of G. mirabilis Hsc70 was assessed with an in vitro refolding assay where the percent refolding of thermally denatured luciferase was monitored using a luminometer. Assays were conducted from 10–40 °C, a range of temperatures that is ecologically relevant for this estuarine species. The results showed that isolated Hsc70 displayed chaperone characteristics in vitro, and was relatively thermally insensitive across the range of experimental temperatures. In addition, the thermal stability of the luciferase refolding capacity of Hsc70 was relatively stable, with refolding activity occurring as high as 50 °C. Overall, Hsc70 from G. mirabilis displayed thermal properties in vitro that suggest that the molecular chaperone is capable of binding and chaperoning proteins at temperatures that the goby encounters in nature.