A CONTRACTILE PROTEIN FROM LEUCOCYTES - ITS EXTRACTION AND SOME OF ITS PROPERTIES

1. 1. A contractile protein was isolated from equine leucocytes. The protein exhibited superprecipitation at low ionic strength in presence of Mg2+ and ATP and possessed ATPase (EC 3.6.1.3) activity. The effect of divalent cations, Mg2+ and Ca2+, on the ATPase activity resembled that on actomyosin from muscle. 2. 2. Electron micrographs of the protein showed, at high ionic strength without ATP, the arrowhead" structure characteristic of myosin B from striated muscle. Thick and thin filaments were observed at low ionic strength at a relatively high ATP level. 3. 3. The possible role of the protein in the movement of leucocytes is discussed. © 1969."