コイF-アクチンの変性におよぼすKCl濃度の影響

抄録

To study the influence of KCl concentrations on denaturation of carp F-actin, F-actin solutions were stored at 3°C in each KCl solution of 0.1, 0.6 and 1.0_M. Viscosity, total and reactive SH groups, and bound nucleotide were measured during storage, and the protective effects of K₂-Na₁ phosphate buffer, sodium glutamate and ATP on salt denaturation were investigated.
The reduced viscosity and the bound nucleotide drastically decreased in the 0.6 and 1.0_M KCl solutions, and in the case of the 0.6_M KCl solution, the decrease in the reduced viscosity occurred within 3-5h. The total SH groups gradually decreased during storage and the reactive SH groups increased by 2 mol SH/mol of G-actin within 20h after introduction into the 0.6_M KCl solution. Three additives, such as ATP, phosphate buffer and sodium glutamate showed protective effects on denaturation and the appearance of latent SH groups was prevented in these cases. In the case of the synthetic actomyosin, reconstituted by mixing myosin and F-actin which were stored separately in 0.6_M KCl solutions, actin-activated Mg-ATPase activity decreased during storage. However, myosin Ca-ATPase activity (in the presence of 0.5_M KCl) remained at its original value.
The above findings show that the structure of carp F-actin is easily changed from its fila-mentous state to small-sized actin or aggregations under higher KCl concentrations, the release of bound nucleotide from actin occurs, and that the latent SH groups of actin molecules appear as a result of denaturation.