The Myosin B from carp and white croaker muscles were treated at 10° in a medium con-taining 1.0 M NaCl and 40mM Tris-maleate (pH 7.0), and the myosin B was taken out for dialysis against 0.5M KCl-40mM Tris-maleate(pH 7.0).
The denaturation of the treated myosin B were measured after a lapse of time by changes of ATPase activities, viscosities with and without ATP, the ultracentrifugal sedimentation pattern, the subunits composition by SDS-polyacrylamide gel electrophoresis, and gel filtration profile on Sepharose Cl-4B.
Under the condition, white croaker myosin B was denatured noticeably but carp myosin Bwas almost negligible. It was further found that myosin B from white croaker and the dissocia-tion into actin and myosin accompanied rapid loss of myosin-binding ability of actin and relativelyslowed the inactivation of myosin ATPase.