[Effect of 2,3-dimercaptopropanol on electron transfer in the energy coupling site 2 of the respiratory chain: evidence for the Q-cycle hypothesis].

Incubation of submitochondrial particles from bovine heart with 2,3-dimercaptopropanol (British antilewisite, BAL) results in inhibition of the respiratory chain between cytochromes b and c. BAL exerts no pronounced effect on the spectral and redox properties of cytochromes b566 and b562. In the BAL-treated submitochondrial particles antimycin brings about the bathochromic shift of the cytochrome b562 absorption alpha-band, but does not induce "extra-reduction" of cytochromes b. Upon a combined effect of antimycin and BAL the reduction of cytochromes b by succinate is inhibited. Whereas neither antimycin nor BAL alone prevents this reaction. The data obtained suggest the existence of two pathways of electron transfer from succinate to cytochromes b, one of which is blocked by antimycin and the other one by BAL. These two pathways form a cyclic loop of electron transport, in accordance with the Mitchell's "protonmotive CoQ-cycle" hypothesis. The traditional scheme of linear arrangement of the respiratory carriers in the succinate--cytochrom c reductase span of the electron transfer chain, as well as the Wikstrom--Berden's branched model, do not provide satisfactory explanation of the mode of BAL inhibitory action.