Regulation and mechanism of action of the small heat shock protein from the hyperthermophilic archaeon Pyrococcus furiosus

The small heat shock protein (sHSP) from the hyperthermophile Pyrococcus furiosus was specifically induced at the level of transcription by heat shock at 105 degreesC. The gene encoding this protein was cloned and overexpressed in Escherichia coli. The recombinant sHSP prevented the majority of E. coli proteins from aggregating in vitro for up to 40 min at 105 degreesC. The sHSP also prevented bovine glutamate dehydrogenase from aggregating at 56 degreesC. Survivability of E. coli overexpressing the sHSP was enhanced approximately sixfold during exposure to 50 degreesC for 2 h compared with the control culture, which did not express the sHSP. Apparently, the sHSP confers a survival advantage on mesophilic bacteria by preventing protein aggregation at supraoptimal temperatures.