The carp myosin B solution was frozen and stored at -3, -5, -10 and -20°C, in order to make clear the freeze denaturation of the protein caused by the concentrated KCI solution on the basis of the thermal inactivation mode of Ca-ATPase. The same manner was also carried out for the myosin B in 1.33M KCI solution under the unfreezing conditions of +3 and -5°C.
In the case of -3 and -20°C frozen storages, the thermal inactivation mode of Ca-ATPase changed from the single-phased first-order plots to the two-phased first-order plots after 11 and 3 days, respectively. In the case of -5 and -10°C frozen storages, the same phenomenon occurred after 6.5h; the apparent rate was larger at -10°C than at -5°C. The order of influence on storage temperature was -10°C>-5°C>-3°C, in the range-of-3 ?? -10°C. When the myosin B in 1.33M KCI solution was stored at-5°C (unfreezing condition), the two-phased first-order inactivation mode was found after 7h, and at +3°C after 26h. The single-phased first-order inactivation mode was restored on addition of carp F-actin to the myosin B which was changed to show the two-phased first-order one after frozen storage at -5°C for 12h and after unfrozen storage in 1.33M KCI solution at -5°C for 9h.
From these findings, we concluded that a portion of F-actin in carp myosin B which was frozen and stored in the range of -3 ?? -10°C, was denatured as a result of the exposure to con-centrated KCI solution; under this range, a lower temperature that is a higher KCI concentration had an accelerating effect on the denaturation of F-actin.