Isolation, purification and characterization of myosin B from myxomycete plasmodium

Abstract

1. 1. Methods have been developed for the isolation of myosin B-like protein (plasmodium myosin B) from a myxomycete plasmodium. 2. 2. Purified plasmodium myosin B has an ATP sensitivity and an ATPase activity as high as those of myosin B from rabbit striated muscle. 3. 3. Mg 2+ increases the rate of superprecipitation of myosin B, while Ca 2+ inhibits its extent. Superprecipitation never takes place in the presence of EDTA. When Mg 2+ is added together with EDTA or ethylene glycol bis(β- aminoethyl ether)-N,N′- tetraacetate , strong and rapid superprecipitation occurs. 4. 4. Electronmicrographs of myosin B show that myosin B is a filament having a diameter of about 100 Å. Globular particles of myosin A attach to the surface of the filament. When ATP is added to it, (natural) F-actin appears (75 Å in diameter). Natural F-actin has the double-stranded helical structure, half a pitch of which is 350 to 420 Å. 5. 5. Myosin A-like protein (plasmodium myosin A) has been isolated by ultracentrifugation of myosin B solution in the presence of ATP and Mg 2+. Plasmodium myosin A can combine with plasmodium F-actin and muscle F-actin to form actomyosin-like complexes. Some physicochemical properties of purified plasmodium myosin A are reported.