Quantized velocities at low myosin densities in an in vitro motility

An in vitro motility assay has been developed in which single actin filaments move on one or a few heavy meromyosin (HMM) molecules. This movement is slower than when many HMM molecules are involved, in contrast to analogous experiments with microtubules and kinesin. Frequency analysis shows that sliding speeds distribute around integral multiples of a unitary velocity. This discreteness may be due to differences in the numbers of HMM molecules interacting with each actin filament where the unitary velocity reflects the activity of one HMM molecule. The value of the unitary velocity predicts a step size of 5–20 nm per ATP, which is consistent with the conventional swinging crossbridge model for myosin function.

[1]  C. Schutt,et al.  Molecular packing in profilin: actin crystals and its implications. , 1989, Journal of molecular biology.

[2]  Toshio Yanagida,et al.  Sliding distance of actin filament induced by a myosin crossbridge during one ATP hydrolysis cycle , 1985, Nature.

[3]  James A. Spudich,et al.  Myosin subfragment-1 is sufficient to move actin filaments in vitro , 1987, Nature.

[4]  G. Schulz,et al.  Induced-fit movements in adenylate kinases. , 1990, Faraday discussions.

[5]  J. Spudich,et al.  An approach to reconstituting motility of single myosin molecules , 1991, Journal of Cell Science.

[6]  Y. Goldman,et al.  Relaxation of muscle fibers with adenosine 5'-[gamma-thio]triphosphate (ATP[gamma S]) and by laser photolysis of caged ATP[gamma S]: evidence for Ca2+-dependent affinity of rapidly detaching zero-force cross-bridges. , 1988, Proceedings of the National Academy of Sciences of the United States of America.

[7]  E. Eisenberg,et al.  Evidence for cross-bridge attachment in relaxed muscle at low ionic strength. , 1982, Proceedings of the National Academy of Sciences of the United States of America.

[8]  J. Spudich,et al.  Myosin step size. Estimation from slow sliding movement of actin over low densities of heavy meromyosin. , 1990, Journal of molecular biology.

[9]  J. Spudich,et al.  The myosin step size: measurement of the unit displacement per ATP hydrolyzed in an in vitro assay. , 1990, Proceedings of the National Academy of Sciences of the United States of America.

[10]  A. Huxley,et al.  Proposed Mechanism of Force Generation in Striated Muscle , 1971, Nature.

[11]  T. Yanagida,et al.  Mechanochemical coupling in actomyosin energy transduction studied by in vitro movement assay. , 1990, Journal of molecular biology.

[12]  A. Huxley.  Muscle structure and theories of contraction. , 1957, Progress in biophysics and biophysical chemistry.

[13]  F. Oosawa,et al.  Protein motors and Maxwell's demons: does mechanochemical transduction involve a thermal ratchet? , 1990, Advances in biophysics.

[14]  A. Hudspeth,et al.  Movement of microtubules by single kinesin molecules , 1989, Nature.

[15]  J. Spudich,et al.  Fluorescent actin filaments move on myosin fixed to a glass surface. , 1986, Proceedings of the National Academy of Sciences of the United States of America.

[16]  L. Goldstein,et al.  Bead movement by single kinesin molecules studied with optical tweezers , 1990, Nature.

[17]  H E Huxley,et al.  The Mechanism of Muscular Contraction , 1965, Scientific American.