title: The competition between adenosine triphosphate and inorganic pyrophosphate for myosin and its suppression by substoichiometric actin concentrations.
abstract: Inorganic pyrophosphate (PPi) inhibits not only Mg2+-ATPase activity of myosin subfragment 1 (S-1) but abolishes also the ATP-induced increment of tryptophan fluorescence of subfragment 1. At the concentrations used (25-50 micron ATP, 12 mm PPi) these effects of PPi were abolished by substoichiometric actin concentrations (approx. 0.1 microM actin vs. approx. 1 microM S-1), where ATPase activity was barely stimulated by actin.
mesh_terms: D000199:Actins / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase; D011756:Diphosphates / Q000378:metabolism*; D007700:Kinetics; D009132:Muscles / Q000378:metabolism; D015879:Myosin Subfragments; D009218:Myosins / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D011485:Protein Binding; D011817:Rabbits; D013050:Spectrometry, Fluorescence
chemical_list: D000199:Actins; D011756:Diphosphates; D015879:Myosin Subfragments; D010446:Peptide Fragments; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D017301:Ca(2+) Mg(2+)-ATPase; D009218:Myosins