title: ATPase activity and filament formation of partially purified myosin from leucocytes.
abstract: Myosin was isolated from leucocytes in horse arterial blood by the same procedures used for the isolation of myosin from skeletal muscle. The Ca2+-, EDTA-, and Mg2+-ATPase [EC 3.6.1.3] activities of the protein was 0.148, 0.147, and 0.001 mumoles/min/mg, respectively, in 0.5 M KCl at pH 7.0 and 25 degrees. The Ca2+-ATPase activity decreased with decrease in the ionic strength. No difference was found between leucocyte myosin and skeletal myosin in the pH profiles of Ca2+- and EDTA-ATPases. The rate and amount of the initial burst of Pi liberation of leucocyte myosin were 0.002 mumoles/min/mg and 0.83 moles/4.8 X 10(5)g,  respectively. Leucocyte myosin aggregated into filaments of 0.3 mum length and 150 A diameter, which had a bare shaft and irregular projections. At high ionic strength, the protein bound to skeletal muscle F-actin to form a complex with the characteristic arrowhead structure.
mesh_terms: D000205:Actomyosin / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000097:blood*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D003593:Cytoplasm / Q000648:ultrastructure; D004492:Edetic Acid / Q000494:pharmacology; D006736:Horses; D007962:Leukocytes / Q000378:metabolism* / Q000648:ultrastructure; D008274:Magnesium / Q000494:pharmacology; D009132:Muscles / Q000378:metabolism; D009218:Myosins / Q000097:blood / Q000302:isolation & purification / Q000378:metabolism*; D009994:Osmolar Concentration; D011189:Potassium Chloride / Q000494:pharmacology; D011485:Protein Binding; D011817:Rabbits
chemical_list: D011189:Potassium Chloride; D000205:Actomyosin; D004492:Edetic Acid; D000251:Adenosine Triphosphatases; D009218:Myosins; D008274:Magnesium; D002118:Calcium