Coupling between redox and acid-base energy by cytochrome b-564 in Baker's yeast mitochondria.
Baker's yeast mitochondrial cytochrome b-564 is characterized by exhibiting both a labile pH-independent high-potential form (E'o, pH 7 = + 190 mV) and a stable pH-dependent (pKa = 6.8) low-potential form (E'o, pH 7 = + 70 mV). The different behavior of these two forms of cytochrome b-564 versus pH seems to be a decisive factor for transduction of redox energy into acid-base energy in oxidative phosphorylation site 2. Deenergizing treatments, such as ADP plus Pi, result in the conversion of all the mitochondrial cytochrome b-564 into its low-potential form, whereas energization with ATP specifically transforms the cytochrome into its high-potential form, the ATP effect being neutralized by the ATPase inhibitor oligomycin and by the uncoupler FCCP. Accordingly, a minimal model for coupling between redox energy and acid-base energy through an electronically energized and protonated ferricytochrome b-564 intermediate is proposed. The energy-transducing properties of mitochondrial cytochrome b-564 seems to be shared by chloroplast cytochrome b-559.
D000136:Acid-Base Equilibrium; D000244:Adenosine Diphosphate / Q000494:pharmacology; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D003573:Cytochrome b Group / Q000378:metabolism*; D008928:Mitochondria / Q000201:enzymology*; D009840:Oligomycins / Q000494:pharmacology; D010084:Oxidation-Reduction; D010710:Phosphates / Q000494:pharmacology; D012441:Saccharomyces cerevisiae / Q000201:enzymology*
D003573:Cytochrome b Group; D009840:Oligomycins; D010710:Phosphates; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D000244:Adenosine Diphosphate