A modulator domain controlling thermal stability in the Group II chaperonins of Archaea

► Hyperthermophilic chaperonins (Cpn) are highly stable yet conserved with other archaeal HSP60s. ► The C-termini contain highly charged sections, divergent from mesophilic archaeal Cpns. ► Mutation of the thermophile domain to reduce charge produced “cold-adapted” (Topt 40 °C) variants. ► Mutants with depressed Topt showed enhanced folding of mesophilic enzymes. ► Raised optimal temperature in Cpn from a psychrophile by chimera formation with the C-terminus of hyperthermophilic Cpn60.