Kinetic studies on the association and dissociation of myosin subfragment 1 and actin.
The reactions of pyrene-labeled actin with myosin subfragment 1 (S1) and S1-ligand complexes at low ionic strength are described by the schemes [formula: see text] where M refers to a myosin head; A is actin; L is ligand; the asterisk refers to a high fluorescence state of actin; and K1 and K3 are association constants. K1 is reduced approximately 10-fold for M.ADP or M.pyrophosphate versus M alone. The rate constant of the isomerization step (k2) is 150-200 s-1 for A*M, A*M.ADP, and A*M-pyrophosphate (20 degrees C). The interaction between the ligand the actin binding sites reduces K2 from 2,000 for A*M to 50-100 for A*M.ADP and to approximately unity for A*M-pyrophosphate. The A*M.ADP state is equated with the AM'.ADP state of Sleep and Hutton (Sleep, J., A., and Hutton, R. L. (1980) Biochemistry 19, 1276-1283).
Taylor
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Department of Molecular Genetics and Cell Biology, University of Chicago, Illinois 60637.
D000199:Actins / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000378:metabolism; D000266:Adenylyl Imidodiphosphate / Q000378:metabolism; D000818:Animals; D011756:Diphosphates / Q000378:metabolism; D007700:Kinetics; D008433:Mathematics; D008962:Models, Theoretical; D009132:Muscles / Q000378:metabolism; D015879:Myosin Subfragments / Q000378:metabolism*; D011817:Rabbits
D000199:Actins; D011756:Diphosphates; D015879:Myosin Subfragments; D000266:Adenylyl Imidodiphosphate; D000244:Adenosine Diphosphate