DEUTERATION CAUSES THE DECREASED INDUCTION OF HEAT-SHOCK PROTEINS ANDINCREASED SENSITIVITY TO HEAT DENATURATION OF PROTEINS IN CHLORELLA

Deuterated Chlorella (D-Chlorella) cells were obtained by cultivation in a medium that contained D2O. The modification of cell components by deuterium (D) increased the heat sensitivity of cells, which depended on the extent of deuteration. To elucidate the mechanism of the D-ind uced increase in the heat sensitivity, the effect of incorporation of D on the denaturation of proteins was investigated. Proteins obtained from D-Chlorella cells, when preheated at 37-degrees-C, were aggregate d to a greater extent than those from H-Chlorella against the heating at 45-degrees-C. The rate of synthesis of heat-shock proteins (hsps) i n D-Chlorella was consistently lower than that in H-cells. Furthermore , an experiment in vitro indicated that deuterated proteins denatured more rapidly than normal proteins upon heating at 60-degrees-C.