title: Dicyclohexylcarbodiimide blocks proton ejection and affects antimycin binding but not electron transport in complex III from yeast mitochondria.
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.
mesh_terms: D000968:Antimycin A / Q000378:metabolism*; D002234:Carbodiimides / Q000494:pharmacology*; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology*; D004579:Electron Transport / Q000187:drug effects; D014450:Electron Transport Complex III; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000378:metabolism*; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D011522:Protons; D011808:Quinone Reductases / Q000378:metabolism*; D015003:Yeasts / Q000378:metabolism*
chemical_list: D002234:Carbodiimides; D009097:Multienzyme Complexes; D011522:Protons; D004024:Dicyclohexylcarbodiimide; D000968:Antimycin A; D009247:NADH, NADPH Oxidoreductases; D011808:Quinone Reductases; D014450:Electron Transport Complex III