ピロリン酸塩とMgCl₂の存在下で起るコイ・ミオシンBの変性機構

抄録

The changes in biochemical and physico-chemical properties of carp myosin B, induced by addition of inorganic pyrophosphate (PPi) and MgCl₂ were investigated.
The myosin B solution (0.3 or 0.5M KCl-40mM Tris buffer, pH 7.0) was mixed with PPi and MgCl₂ giving a final concentration of each 1m_M. Soon after or after storage for various periods at 10°C, the mixture was dialyzed overnight to exclude PPi and MgCl₂ and fractionated by centri-fugation at 79, 000×g for 5h at 5°C. The supernatant thus obtained was used for measurements viscosity, its ATP-sensitivity, thermal inactivation mode of Ca-ATPase activity, and subunits composition.
These results indicated that when PPi and MgCl₂ were mixed, 45% of myosin B weight value was reversibly dissociated into actin and myosin, but 40% of it was irreversibly transformed to unsedimented form of actomyosin by ultracentrifugal fractionation. As the storage time was prolonged, these alterations gradually proceeded further.