BINDING OF ADENOSINE TRIPHOSPHATE TO MYOSIN

NaCl is a noncompetitive inhibitor of the Mg2+-adenosine triphosphate phosphohydrolase activities of myosin and heavy meromyosin. By employing gel filtration chromatography in the presence of [γ-32P]-adenosine triphosphate and 1.50 M NaCl, both myosin and heavy meromyosin were observed to bind 1.6 and 1.7 moles of adenosine triphosphate per mole of protein, respectively. The binding of adenosine triphosphate by myosin required Mg2+, was inhibited by adenosine diphosphate and inorganic pyrophosphate but was unaffected by inorganic phosphate. Both myosin and heavy meromyosin appeared to be labeled when precipitated in the presence of [14C]- or [32P]adenosine triphosphate by rapid addition of neutral (NH4)2SO4. The labeling of myosin with radioactive adenosine triphosphate required Mg2+ and showed a typical adenosine triphosphate saturation curve. It was also inhibited by adenosine diphosphate. When myosin labeled with (γ-32P]adenosine triphosphate was dissolved in 10 M urea or washed with cold 0.020 M acetate and 1.50 M NaCl (pH 4.5), the radioactivity was released as inorganic phosphate. © 1968, American Chemical Society. All rights reserved.