Homogeneity of the outer mitochondrial membrane. Studies on the fragments obtained through lysis by ascorbate

Abstract

Outer mitochondrial membranes from rat liver undergo a structural lysis when incubated in the presence of 1 mM ascorbate. The fragments produced can be separ­ ated by differential centrifugation. Three fractions were obtained, one sedimenting at 22,000 X g, another at 100,000 X g and a supernatant from this last centrifugation. The lipid composition and the distribution of enzyme markers monoamine oxidase and rotenone-insensitive NADH-cyt. c reductase in these three fractions has been studied. The supernatant fraction was composed of solubilized proteins accompanied by some altered phospholipids and negligible amounts of cholesterol. The other two fractions were rather similar in distribution of enzymes and lipid composition. An interpretation of the results presented indicate that the outer mitocondrial membrane is rather homo­ geneous in what refers to distribution of their lipid and protein components, contrary to what has been established for the inner membrane.