Circular-dichroism studies of the cytochrome b-c1 complex of Saccharomyces cerevisiae.

1. Circular dichroism studies on the Soret region of the cytochrome b-c1 complex of yeast reveal a change in the dichroism of cytochrome c1 depending on the redox state of cytochrome b, indicating a conformational interaction between both cytochromes. 2. This interaction is not influenced by binding of the inhibitor antimycin A to the complex, so that the interaction does not appear to be involved in the mechanism of electron transport through the complex. 3. Antimycin A binding causes a complex set of changes in the CD spectrum of the complex, which can be attributed to a severe and specific distortion of the environment of the chromophore of cytochrome b.