EFFECTS OF A DISULFIDE (ELLMANS REAGENT) AND THIOLS ON OXIDATIVE PHOSPHORYLATION AND ION TRANSPORT BY RAT LIVER MITOCHONDRIA

The disulfide, 5,5′-dithio-bis-2-nitrobenzoic acid (DTNB), inhibits oxidative phosphorylation and uptake of calcium and phosphate ions by rat liver mitochondria. Half-maximal inhibition of oxidative phosphorylation is obtained with an amount of inhibitor of approximately 5 nmoles/mg of protein. Complete inhibition of oxidative phosphorylation and uptake of phosphate as well as abolition of phosphate-linked calcium uptake results from preincubation of mitochondria with DTNB followed by removal of excess inhibitor by washing. DTNB-treated mitochondria can be restored to normal function by additional incubation with dithiothreitol (DTT) followed by removal of excess DTT by washing. Oxidative phosphorylation during state 3 respiration can be completely stopped by DTNB and restored by DTT. It is concluded that one or more highly reactive -SH groups are essential for oxidative phosphorylation and ion transport in mitochondria. © 1969.