LOCALIZATION OF ATRACTYLOSIDE-SENSITIVE NUCLEOTIDE BINDING SITES IN RAT LIVER MITOCHONDRIA

The inner membrane of the mitochondrion has been confirmed as the locus of atractyloside-sensitive adenine nucleotide binding. These binding sites were found in both inner and outer membrane fractions prepared by the digitonin fractionation procedure. However, binding by the outer membrane fraction was shown to be due to contamination by inner membrane. This was demonstrated by the effect of excess digitonin on the outer membrane fraction: the outer membrane marker-enzymes and phospholipid were solubilized while the ADP binding sites were not. The properties of the binding sites of both fractions were also shown to be identical. An inhomogeneous distribution of atractyloside-sensitive binding sites on the inner membrane was indicated by the observation that the ratio of ADP binding sites to cytochrome oxidase activity of the fragments of inner membrane contaminating the outer membrane fraction was greater than the ratio in the inner membrane fraction. © 1969.