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To eliminate the gap between the biochemistry of actomyosin in solution and the physiology of contracting muscle, we developed an in vitro force-movement assay system in which the steady-state force-velocity relation in the actin-myosin interaction can be studied. The assay system consists of the internodal cells of an alga, Nitellopsis obtusa, containing(More)
We have examined the temperature-dependence of sliding velocity of fluorescent F-actin on myosins isolated from 10 degrees C- and 30 degrees C-acclimated carp. Activation energies for the sliding of F-actin were 63 and 111 kJ/mol for the 10 degrees C- and 30 degrees C-acclimated carp myosins, respectively. Arrhenius plots of the sliding velocity from 10(More)
Although evidence has been presented that, at low ionic strength, myosin heads in relaxed skeletal muscle fibers form linkages with actin filaments, the effect of low ionic strength on contraction characteristics of Ca(2+)-activated muscle fibers has not yet been studied in detail. To give information about the mechanism of muscle contraction, we have(More)
When uncoated polystyrene beads suspended in Mg-ATP solution were introduced into the internodal cell of an alga Chara corallina, the beads moved along the actin cables with directions and velocities (30-62 microns s-1) similar to those of native cytoplasmic streaming. Bead movement was inhibited both in the absence of ATP and in the presence of CA2+, as(More)
To provide information on the mechanism of cardiac adaptation at the molecular level, we compared the unitary displacements and forces between the 2 rat cardiac myosin isoforms, V1 and V3. A fluorescently labeled actin filament, with a polystyrene bead attached, was caught by an optical trap and brought close to a glass surface sparsely coated with either(More)
Movement generated by the myosin motor is generally thought to be driven by distortion of an elastic element within the myosin molecule and subsequent release of the resulting strain. However, the location of this elastic element in myosin remains unclear. The myosin motor domain consists of four major subdomains connected by flexible joints. The SH1 helix(More)
Despite >50 years of research work since the discovery of sliding filament mechanism in muscle contraction, structural details of the coupling of cyclic cross-bridge movement to ATP hydrolysis are not yet fully understood. An example would be whether lever arm tilting on the myosin filament backbone will occur in the absence of actin. The most direct way to(More)
To elucidate the molecular mechanism of muscle contraction resulting from the ATP-dependent actin-myosin interaction, we constructed an assay system with which both the force and the movement produced by the actin-myosin interaction in vitro can be simultaneously recorded and analyzed. The assay system consisted of the giant internodal cells of an alga,(More)
Although muscle contraction is known to result from movement of the myosin heads on the thick filaments while attached to the thin filaments, the myosin head movement coupled with ATP hydrolysis still remains to be investigated. Using a gas environmental (hydration) chamber, in which biological specimens can be kept in wet state, we succeeded in recording(More)
In order to study ATP turnover during shortening and lengthening of rabbit psoas myofibrils, we have used fluorescence microscopy in which the displacement of a fluorescent nucleotide analog, 2'(3')-O-[N-[2-[[Cy3] amido] ethyl] carbamoyl]-adenosine 5' triphosphate (Cy3-EDA-ATP) bound to cross-bridge on flash photolysis of caged ATP was measured [Chaen et(More)