Stabilizing effect of Ca2+ on myosin and myofibrils of squid mantle muscle as affected by heating conditions

Abstract

Suppressive effect of Ca 2+ on the thermal denaturation of myosin and on myofibrils of squid mantle muscle was compared. Its stabilization effect on myosin was smaller than that on myofibrils, and was not affected by KCl concentration. The stabilizing effect of Ca 2+ on myosin decreased with lowering the temperature for heating showing no stabilization at 20 °C, while the effect on myofibrils was evenly detected at all temperatures tested. Stabilizing effect of Ca 2+ on myosin disappeared even at 30 °C in the presence of sorbitol showing a small inactivation rate, while the effect of Ca 2+ was equally detected on myofibrils irrespective of the reduction of inactivation rate with sorbitol. Stabilization of myosin by Ca 2+ again appeared even in the presence of sorbitol by raising the heating temperature to 38 °C. It was suggested that Ca 2+ confers stabilization on myosin only when myosin is in under unstable conditions. Stabilization effect of Ca 2+ on myosin was enhanced upon F-actin binding, namely Ca 2+ bound myosin was more significant stabilized by F-actin binding, and the effect was no longer affected by the conditions for heating.

Effect of calcium ion on the thermal denaturation of subfragment-1 and rod regions of squid myosin upon the heating of myofibrils

“…We confirmed the CaCl 2 concentration 6 in Ca-medium was high enough for a full stabilization of myosin [12]. Heating temperature was optionally changed.…”

“…The effect of Ca 2+ was found in myofibrils more significantly than in myosin or S-1 [7,12]. However, effect of Ca 2+ on rod portion has not been studied yet.…”