Isolation and some properties of oligomycin-sensitive adenosine triphosphatase from beef heart mitochondria and its morphological study

1. To have a rapid isolation of oligomycin-sensitive ATPase particles (OSA particles), 0.1 mg DOC per mg of protein and 72 g potassium chlo. ride per I were added to mitochondria suspended in a tris.sucrose-histidine solution, which was followed by addition of 2-fold volume of chilled water, and fractionated by a discontinuous sucrose density gradient centrifugation. As a result, it was possible to reveal the OSA particle structure, composed of the head piece, stalk and thread-like structure of a superficial portion of the base pieces, stripped off from the mitochondrial inner membrane, in a layer of density.l.lO. This fraction exhibited a remarkable activity of ATPase sensitive to oligomycin, approximately 15 ,lJ.moles Pi released per mg of protein per minute at pH 8.6 at 37° in a non-ATP regenerating assay system, and contained almost no cytochromes. 2. When the OSA particles thus isolated were heated in water bath at 65° for 2 minutes, the head pieces were detached with a concomitant loss of oligomycin-sensitivity and were purified from the supernatant by precipitation with ammonium sulfate. 3. Trypsin in low concentration slightly induced a rise in the ATPase activity of OSA particles but in higher concentration it inhibited the activity. 4. OSA particles were resistant to the treatment of urea, and it was difficult to detach the head pieces by this treatment. 5. The some fraction obtained by solubilization of thc crude OSA particles with cholate and fractionation with ammonium sulfate exhibited ATPase activity in a masked form, and the ATPase activity with oligomycin. sensitivity was restored on addition of phospholipid. 6. A discussion was made on the mode of assembly of the head pieces and associated components and biochemical properties of OSA particles.