D. Oxidized mitochondria with the radioactive single-cysteine Bax protein pair or double-cysteine Bax protein were prepared as in (B). After an aliquot was withdrawn as input, another aliquot was extracted by Na2CO3 (pH 11.5) and centrifuged through a sucrose cushion to separate the integral proteins in the membrane pellet from the soluble and peripheral proteins in the supernatant. The input, pellet and supernatant were analyzed by non-reducing SDS-PAGE and phosphor-imaging. In a parallel control experiment, the pellet and supernatant were analyzed by reducing SDS-PAGE and immunoblotting with an antibody specific to PDHE1α, a soluble mitochondrial matrix protein. 