Figure 7.

p4 and/or redp4 are able to reduce cytochrome c₁ or cytochrome c and form dimers in the presence of cytochrome bc₁. A, comparison of the ability of p4 to reduce cytochrome c₁ of cytochrome bc₁ (black) and cytochrome c (white). The concentrations of cytochromes and p4 were 6 μm and 60 μm, respectively. Cytochrome bc₁ was fully oxidized by ferricyanide prior addition of p4. Cytochrome c was almost fully oxidized prior addition of p4. Conditions were 50 mm Tris (pH 8.0), 100 mm NaCl, 1 mm EDTA, and 0.01% n-dodecyl-d-maltoside. Measured data points were fitted to the linear function. All linear coefficients of determination (R²) were above 0.95. B, reduction of cytochrome c₁ of cytochrome bc₁ in the presence of redp4 (black circles), oxp4 (black rectangles), or the (VP20)CA variant (white diamonds). The concentration of cytochrome bc₁ and peptides was 6 μm. Cytochrome bc₁ was fully oxidized by ferricyanide prior addition of peptides. C, the indicated concentrations of FITC-p4 were incubated with 6 μm cytochrome bc₁ for 10 min as described in A. p4 was then analyzed by SDS-PAGE, followed by gel imaging.