Abstract
1. 1. Durohydroquinone (H 2DQ), a specific reductant for the second phosphorylation site, has been used in the study of the fast reduction kinetics of cytochromes b. 2. 2. In ubiquinone-extracted mitochondria, H 2DQ reduces cytochrome(s) b in a fast reaction, the rate and extent of which decreases upon reincorporation of ubiquinone. 3. 3. In cytochrome c-extracted mitochondria, H 2DQ reduces both cytochromes b. After ATP addition, with cytochrome b T reduced by endogenous substrate, H 2DQ reduces cytochrome b K at a slow rate whereas ubiquinone readily accepts reducing equivalents. In the presence of uncoupler, H 2DQ reduces cytochrome b K at a faster rate while ubiquinone behaves as a less efficient electron acceptor. Under these conditions, cytochrome b T is not reduced by H 2DQ. 4. 4. Cytochrome c 1 reduction can be resolved free of cytochrome c interference in cytochrome c-extracted mitochondria. Cytochrome c 1 reduction is 4 times faster in the presence of uncoupler than in the presence of ATP. 5. 5. Addition of cytochrome c to cytochrome c-extracted mitochondria stimulates the rate of cytochromes b reduction. 6. 6. In intact mitochondria, ATP addition causes 20 % reduction of cytochrome b T and speeds up the initial rate of cytochromes b reduction by a factor of 10. 7. 7. Addition of antimycin A to intact mitochondria results in 80–100 % reduction of cytochrome b K by endogenous substrate. ATP added to antimycin A-inhibited mitochondria produces oxidation of cytochrome b K and simultaneous and variable reduction of cytochrome b T. This latter effect is reverted by the addition of an uncoupler.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
More From: Biochimica et Biophysica Acta (BBA) - Bioenergetics
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.