Acceleration of the sliding movement of actin filaments with the use of a non-motile mutant myosin in in vitro motility assays driven by skeletal muscle heavy meromyosin.

Acceleration of the sliding movement of actin filaments with the use of a non-motile mutant myosin in in vitro motility assays driven by skeletal muscle heavy meromyosin.

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We examined the movement of an actin filament sliding on a mixture of normal and genetically modified myosin molecules that were attached to a glass surface.For this purpose, we used a Dictyostelium G680V mutant myosin II whose release rates of Pi and ADP were highly suppressed relative to normal myosin, leading to a swish supreme glide track white significantly extended life-time of the strongly bound state with actin and virtually no motility.When the mixing ratio of G680V mutant myosin II to skeletal muscle HMM (heavy myosin) was 0.01%, the actin filaments moved intermittently.When they moved, their sliding velocities were about two-fold faster than the velocity of skeletal HMM alone.

Furthermore, sliding movements were also faster when the actin filaments were allowed to slide on skeletal muscle HMM-coated glass surfaces in the motility buffer solution containing G680V HMM.In this case no intermittent movement was observed.When the nitrile gloves in a bucket actin filaments used were copolymerized with a fusion protein consisting of Dictyostelium actin and Dictyostelium G680V myosin II motor domain, similar faster sliding movements were observed on skeletal muscle HMM-coated surfaces.The filament sliding velocities were about two-fold greater than the velocities of normal actin filaments.We found that the velocity of actin filaments sliding on skeletal muscle myosin molecules increased in the presence of a non-motile G680V mutant myosin motor.