Abstract
It has been reported that antimycin lowers the apparent initial rate of reduction of cytochrome c1 in a single turnover, both in succinate cytochrome c oxidoreductase and in the isolated b-c-1 complex (De Vries et al., 1982; Degli Esposti et al., 1982). This finding appears to be inconsistent with Q-cycle as formulated by Mitchell (1976), which envisaged a concerted and antimycin insensitive delivery of electrons from QH2 to cytochrome b566 (bL) and c1 in the pre-steady-state. On these grounds, as well as on the basis of heterogenous kinetics of reduction of the prosthetic groups De Vries et al. (1982) have put forward a modified cyclic mechanism for the electron pathways in the b-c1 complex, in which the enzyme operates as a dimer. In this double Q-cycle model, antimycin inhibits the reduction of cytochrome c1 by QH2 in one monomer, whereas the reduction in the other monomer would be antimycin-insensitive. A double cycle model was also proposed by Linke et al., (1986).
Published Version
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