Figure 3.

Representative original data traces for determination of rates of (A, upper traces) superoxide generation and (B, lower traces) electron transfer in isolated bc₁ and b₆f complexes. The electron transfer and superoxide generation activities were measured as described in Materials and Methods using cytochrome c as the electron acceptor for the yeast cyt bc₁, cyt b₆f from M. laminosus, and cyanobacterial plastocyanin for the b₆f complex from spinach. Traces averaged from two to four measurements are shown. The background fluorescence change measured for the reaction mixture before the addition of the enzyme was subtracted from the superoxide generation activity data (B, lower traces). The arrow indicates addition of 5 nM and 45 nM bc₁ complex, respectively, for reactions in the absence and presence of inhibitor, and 5 nM b₆f complex.