Photoinduced Cyclic Electron Transfer in Rhodocyclus tenuis Cells:  Participation of HiPIP or Cyt c8 Depending on the Ambient Redox Potential

We demonstrate the participation of a cytochrome c8 and a high-potential iron-sulfur protein (HiPIP) in the photoinduced electron transfer in whole cells of Rhodocyclus tenuis depending on the redox state or background continuous illumination. At high redox potentials (above 350 mV) or under a stron...

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Bibliographic Details
Published in:Biochemistry (Easton) 1997-10, Vol.36 (40), p.12183-12188
Main Authors: MENIN, Laure, SCHOEPP, Barbara, PAROT, Pierre, VERMéGLIO, André
Format: Article
Language:English
Subjects:
Absorption
Bacterial Proteins
Cytochrome c Group - metabolism
Electron Transport
Electron Transport Complex III - metabolism
Electron Transport Complex III - physiology
Iron-Sulfur Proteins - metabolism
Lasers
Oxidation-Reduction
Photochemistry
Rhodospirillales - cytology
Rhodospirillales - enzymology
Rhodospirillales - metabolism
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Summary:We demonstrate the participation of a cytochrome c8 and a high-potential iron-sulfur protein (HiPIP) in the photoinduced electron transfer in whole cells of Rhodocyclus tenuis depending on the redox state or background continuous illumination. At high redox potentials (above 350 mV) or under a strong background illumination (5 W m-2), the cytochrome c8 acts as the physiological electron donor to the photo-oxidized high-potential hemes of the tetraheme cytochrome bound to the reaction center. For redox potentials ranging from 200 to 310 mV or under weak background illumination (1. 25 W m-2), the electron carrier is the HiPIP. The electron transfer between cyt c8 and HiPIP and the tetraheme cytochrome has half-times of 300 and 480 micros, respectively. A slow electrogenic phase of the membrane potential is linked to their rereduction. This phase is sensitive to a specific inhibitor of the cyt bc1 complex, indicating involvement of cyt c8 and HiPIP in the photoinduced cyclic electron transfer at these two redox conditions.
ISSN:0006-2960
1520-4995
DOI:10.1021/bi971163b