Inhibition of mitochondrial electron transport by hydroxy-substituted 1,4-quinones

Mitochondrial electron transport from NADH, succinate, or duroquinol to oxygen is inhibited by 5-omega-cyclohexyl-n-pentyl-6-hydroxy-2,3-dimethoxy-1,4-benzoquinone and 2-omega-cyclohexyl-n-pentyl-3-hydroxy-1,4-napthoquinone. Assays of partial electron transport activities indicate a site of inhibition in the region between the site of duroquinol oxidation and cytochrome c reduction. Effects of the inhibitors on cytochrome spectra indicate the principle site of inhibition is between cytochromes of the b group and cytochrome c1. The quinones do not induce increased reduction of the b566 as does antimycin A. The benzoquinone can induce a partial antimycin insensitive bypass of the cytochromes b-c1 region. Uncoupling agents do not affect the extent of inhibition as has been reported for analogous naphthoquinone inhibitors.