Extraction of an actomyosin‐like protein from amoebae of Dictyostelium discoideum

Publisher Website
Google Scholar
Abstract
An actomyosin‐like protein has been extracted from amoebae of Dictyostelium discoideum, V‐12. The purified protein exhibited a reversible change in viscosity upon addition of ATP, indicating an ATP sensitivity of 75–85% and a specific viscosity of 0.1. At low ionic strength in the presence of Mg++ and ATP the amoeba protein displayed the phenomenon of superprecipitation. The protein extract was found to be an adenosinetriphosphatase (ATP'ase) hydrolyzing ATP to ADP and inorganic phosphate. Both Mg++ and Ca++ at low ionic strength accelerated the ATP ase activity whereas at high ionic strength only Ca++ stimulated ATP hydrolysis. The ATP'ase activity was inhibited by ethylene‐diamine‐tetraacetic‐acid, Mersayl and p‐chloromercuribenzoate. The physico‐chemical and enzymatic properties of the extracted amoeba protein are qualitatively comparable to those of muscle actomyosin, and very similar in quantitative properties to smooth muscle actomyosin and the actomyosin‐like proteins of blood platelets, leucocytes and slime mold plasmodia. The significance of the presence of this actomyosin‐like protein in Dictyostelium amoebae is discussed in relation to amoeboid form and movement.