Effect of calcium ion on the thermal denaturation of subfragment-1 and rod regions of squid myosin upon the heating of myofibrils |
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Authors: | Kazuyo Abe Yasunori Kinoshita Kunihiko Konno |
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Institution: | (1) Faculty of Fisheries Sciences, Hokkaido University, Hakodate Hokkaido, 041-8611, Japan;(2) Hokkaido Industrial Technology Center, Hakodate Hokkaido, 041-0801, Japan; |
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Abstract: | Thermal inactivation of Ca2+ ATPase of squid myofibrils was significantly suppressed in the presence of Ca2+. Monomeric myosin content decreased much faster than Ca2+ ATPase inactivation in Ca medium, which was well explained by fast rod denaturation. In contrast, rod denaturation was slower
than S-1 in EDTA medium. The 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 Ca2+ whereas the rod denaturation was not. An unfolding experiment with isolated myosin rod confirmed that there was no stabilizing
effect of Ca2+ on myosin rod. It was concluded that significant stabilization of the S-1 portion by Ca2+ generated the apparently different myosin denaturation patterns in the two media. |
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