Natural chaperonin of the hyperthermophilic archaeum, Thermococcus strain KS‐1: a hetero‐oligomeric chaperonin with variable subunit composition

To study the difference in expression of the chaperonin α‐ and β‐subunits in Thermococcus strain KS‐1 (T. KS‐1), we measured their intracellular contents at various growth temperatures using subunit‐specific antibodies. The β‐subunit was significantly more abundant with increasing temperature (maximum at 93°C), whereas the α‐subunit was not. Native PAGE with Western blot analysis indicated that the natural chaperonins in the crude extracts of T. KS‐1 cells grown between 65°C and 95°C migrate as single bands with different mobility. The recombinant α‐ and β‐subunit homo‐oligomers migrated differently from each other and from natural chaperonins. Immunoprecipitation also showed that the natural chaperonin was the hetero‐oligomer. These results indicate that chaperonin in T. KS‐1 formed a hetero‐oligomer with variable subunit composition, and that the β‐subunit may be adapted to a higher temperature than the α‐subunit. T. KS‐1 probably changes its chaperonin subunit composition to acclimatize to the ambient temperature.