title: Calibration and time resolution of lumenal pH-transients in chromatophores of Rhodobacter capsulatus following a single turnover flash of light: proton release by the cytochrome bc1-complex is strongly electrogenic.
abstract: The flash-induced proton release into the lumen of chromatophores from Rhodobacter capsulatus was studied with Neutral red as pH-indicator. Calibration of the acidification jump after a single flash yielded a much larger figure, at least 0.8 units, than previously thought. A slow kinetic phase of proton release (85-90% of total) was sensitive to inhibitors of the cytochrome bc1-complex. Its half-rise time, about 10 ms, was the same as the rise time of the electrogenic reaction in the cytochrome bc1-complex that was recorded by electrochromism of carotenoids. The oxidoreduction of the two b-hemes was significantly faster (t1/2 approximately equal to 3 ms). Thus the major electrogenic event in the cytochome bc1-complex is proton and not electron transfer.
authors.affiliation: Biophysik, Fachbereich Biologie/Chemie, Universität Osnabrück, Germany.
authors.forename: A Y
authors.initials: AY
authors.lastname: Mulkidjanian
authors.forename: W
authors.initials: W
authors.lastname: Junge
mesh_terms: D020130:Bacterial Chromatophores / Q000378:metabolism*; D002138:Calibration; D004563:Electrochemistry; D014450:Electron Transport Complex III / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008027:Light; D009499:Neutral Red; D010084:Oxidation-Reduction; D011522:Protons; D016354:Rhodobacter capsulatus / Q000378:metabolism*; D013053:Spectrophotometry; D013997:Time Factors
chemical_list: D011522:Protons; D009499:Neutral Red; D014450:Electron Transport Complex III