Regensburg 2010 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
BP: Fachverband Biologische Physik
BP 7: Posters: Biological Machines, Motor Proteins
BP 7.11: Poster
Montag, 22. März 2010, 17:15–20:00, Poster B1
Study of H/D substitution effects on the function of the cytochrome bc1 complex of Rhodobacter capsulatus — •Katrin Jahns1, Natalia Voskoboynikova1, Maria Kozlova1,2, and Armen Mulkidjanian1,2 — 1School of Physics, University of Osnabrück, D-49069 Osnabrück, Germany — 2A.N.Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, 119991, Russia
The cytochrome bc1 complex is a voltage-generating membrane ubiquinol:cytochrome c oxidoreductase [1]. We have studied the effect of the H2O/D2O substitution on the flash-induced turnovers of the cytochrome bc1 complexes in the vesicular preparations of the inner cellular membranes (chromatophores) of phototrophic α-proteobacteria Rhodobacter capsulatus. We traced the kinetics of flash-induced generation of membrane voltage by the cytochrome bc1 complex via the spectral shifts of native carotenoid pigments and correlated them with the kinetics of electron transfer as measured in the same samples. At neutral pH, the kH/kD ratio was ca. 2.3, it dropped below 2 at acidic and alkaline pH. On contrast, the rates of flash-induced cytochrome b reduction were only ca. 1.5 times slower in D2O than in H2O. We conclude that, at physiological pH values, the rate of proton translocation in the cytochrome bc1 complex is limited by the breakage or formation of hydrogen bonds and not by the transmembrane electron transfer in cytochrome b.
[1] A.Y. Mulkidjanian, Photochem Photobiol Sci 6 (2007) 19-34