Key points are not available for this paper at this time.
Abstract 1. The adenosine triphosphatase of rat liver mitochondria is tightly bound to the inner membrane and is solubilized in very poor yield (less than 0.5%) by sonic oscillation procedures alone. Solubilization of the enzyme in good yield (30 to 55%) is obtained by sonic oscillation provided the membranes are first washed exhaustively in low ionic strength buffer and incubated for 16 hours in the presence of ATP and ethylene glycol. Purification of the solubilized enzyme by sequential chromatography on DEAE-cellulose and Sephadex G-200 consistently yields preparations exhibiting a specific activity of approximately 22 µmoles of ATP hydrolyzed per min per mg. 2. The purified enzyme is homogeneous as assessed by gel filtration, sedimentation in sucrose gradients, and sedimentation in the analytical ultracentrifuge. The molecular weight of the ATPase is 384,000 based on determinations of its sedimentation coefficient (s020,w = 12.15), diffusion coefficient (D020,w = 2.96 x 10-7 cm2 sec-1), and partial specific volume (v = 0.740 cm3 g-1). 3. Electrophoresis in two dissociating solvent systems indicates that the enzyme contains three classes of subunits. The molecular weights of the three subunits determined by their electrophoretic mobilities in the sodium dodecyl sulfatemercaptoethanol system are: subunit A, 62,500; subunit B, 57,000; and subunit C, 36,000. 4. The amino acid composition of the purified ATPase from rat liver mitochondria is strikingly similar to amino acid compositions reported for ATPases from such diverse sources as bovine heart mitochondria, spinach chloroplasts, and bacteria. The similarity in chemical and physical properties among these enzymes is discussed in terms of their possibly analogous structural and functional roles in these membrane systems.
Catterall et al. (Sun,) studied this question.