ISOLATION OF AN ACTOMYOSIN-LIKE PROTEIN COMPLEX FROM SLIME MOLD PLASMODIUM AND SEPARATION OF COMPLEX INTO ACTIN- AND MYOSIN-LIKE FRACTIONS

Extracts of the plasmodium of Physarum polycephalum prepared with various homogenization media contained a calcium-activated adenosine triphosphatase and a rapidly sedimenting actin-like protein. When plasmodial extracts prepared with 0.05 m sodium pyrophosphate-0.01 m Tris-maleate (pH 6.8) were fractionated by precipitation with ammonium sulfate, the adenosine triphosphatase and the rapidly sedimenting protein were isolated as a partially purifled actomyosin-like complex. As judged by viscometry, boundary and zone sedimentation, and electron microscopy slime mold actomyosin was basically similar to muscle actomyosin but differed in having a greater solubility at low ionic strength and a lower myosin:actin ratio. After desalting on Sephadex G-25, slime mold actomyosin was resolved into partially purified actin- and myosin-like components by gel chromatography on Sephadex G-200 at low ionic strength. © 1969, American Chemical Society. All rights reserved.