スルメイカ筋原線維の加熱によるミオシン・ サブフラグメント-1およびロッド変性に対するCa2+の影響

摘要

Thermal inactivation of Ca^[2+]-ATPase of squid myofibrils was significantly suppressed in the presence of Ca^[2+]. Monomeric myosin content decreased much faster than Ca^[2+]-ATPase inactivation in Ca-medium, which was well explained by the fast rod denaturation. In contrast, rod denaturation was slower than S-1 in EDTA medium. Decrease in monomeric myosin content was explained by faster S-1 denaturation. Comparing the S-1 and rod denaturation rates at a fixed temperature, it was concluded that S-1 denaturation was suppressed by Ca^[2+] whereas the rod portion was not. Unfolding experiment with isolated myosin rod confirmed no stabilizing effect of Ca2+ on rod. It was concluded that significant stabilization of S-1 portion by Ca2+ generated apparently different myosin denaturation pattern in two media.