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  • Title: Dicyclohexylcarbodiimide blocks proton ejection and affects antimycin binding but not electron transport in complex III from yeast mitochondria.
    Author: Clejan L, Beattie DS.
    Journal: J Biol Chem; 1983 Dec 10; 258(23):14271-5. PubMed ID: 6315724.
    Abstract:
    Treatment of complex III with dicyclohexyldicarbodiimide (DCCD) either before or after incorporation into liposomes resulted in a loss of electrogenic proton movements; however, only minimal decreases in cytochrome c reductase activity were noted in the liposomes containing DCCD-treated complex III. Thus, DCCD appears to act by "uncoupling" proton translocation from electron transport. A decreased sensitivity of the ubiquinol:cytochrome c reductase activity to antimycin was also noted in the DCCD-treated complex III. This loss of sensitivity to antimycin was reflected in a decreased binding of antimycin to the complex after DCCD treatment from 9.5 nmol/mg of protein in the control to 3.8 nmol/mg of protein in the DCCD-treated complex. DCCD also affected the red shift observed after antimycin addition to dithionite-reduced complex III resulting in a broad peak with no sharp maximum. Similarly, DCCD treatment of yeast mitochondria resulted in a complete loss in the red shift after antimycin addition to mitochondria previously reduced with succinate. No loss in enzymatic activity was observed in the DCCD-treated mitochondria. These results suggest that DCCD concomitant with the inhibition of proton ejection in the cytochrome b-c1 region of the respiratory chain causes modifications in the properties of cytochrome b which alter the binding of antimycin without significantly affecting the electron transfer activity of this cytochrome.
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