A CHAPERONIN FROM A THERMOPHILIC BACTERIUM, THERMUS-THERMOPHILUS, THAT CONTROLS REFOLDINGS OF SEVERAL THERMOPHILIC ENZYMES

A chaperonin has been purified from a thermophilic bacterium, Thermus thermophilus. It consists of two kinds of proteins with approximate M(r), 58,000 and 10,000 and shows a 7-fold rotational symmetry from the top view and a "football"-like shape from the side view under the electron microscopic view. Its weak ATPase activity is inhibited by sulfite and activated by bicarbonate. ATP causes change of its mobility in nondenaturating polyacrylamide gel electrophoresis. The T. thermophilus chaperonin can promote in vitro refolding of several guanidine HCl-denatured enzymes from thermophilic bacteria. At high temperatures above 60-degrees-C, where the native enzymes are stable but their spontaneous refoldings upon dilution of guanidine HCl fail, the chaperonin induces productive refolding in an ATP-dependent manner. No or very poor refolding is induced when the chaperonin is added to the solution aged after dilution. An excess amount of the chaperonin is inhibitory for refolding. At middle temperatures (30-50-degrees-C), where spontaneous refoldings of the enzymes occur, the chaperonin arrests refolding in the absence of ATP and refolding is induced when ATP is supplemented. At temperatures below 20-degrees-C, where spontaneous refoldings also occur, the chaperonin arrests the refolding but ATP does not induce refolding.