Prefoldin is a hexameric chaperone that has been identified in eukaryotic cells and in Archaea. E. coli cells over-expressing the prefoldin gene from the hyperthermophilic, archaeum, Pyrococcus furiosus, grew well at 48A degrees C while control cells were unable to grow above 46A degrees C. The isolated and purified Pfu-prefoldin (specially the beta subunit and the prefoldin) thermally protected the activity of lysozyme.