pH-Abhängigkeit der Cytochrom c2 (c)-Reduktion und des Membranpotentials (Δ Ψ) in Modellsystemen und Chromatophoren von Purpurbakterien
✍ Scribed by Alexander V. Oleskin; Prof. Dr. Vitaly D. Samullov
- Publisher
- John Wiley and Sons
- Year
- 1992
- Tongue
- English
- Weight
- 483 KB
- Volume
- 32
- Category
- Article
- ISSN
- 0233-111X
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✦ Synopsis
Abstract
Ubiquinol‐1 reduces cytochrome c in solution at a rate which increases 10‐fold with an increase in pH by one unit within the range of 6.5 – 8.5. Light‐dependent generation of ΔΦ in proteoliposomes containing Rhodospirillum rubrum reaction centers in the presence of ubiquinone‐1 and cytochrome c is also stimulated with an increase in pH from 6.5 to 8.5. The ΔΦ generation in R. rubrum and Rhodobacter sphaeroides is described by a bell‐shaped pH‐dependence curve, the maximum responses being observed at pH 7.5–8.0. The dependence is retained with antimycin A (but not myxothiazol). The magnitude of the residual ΔΦ generation in the presence of myxothiazol or its combination with antimycin remains relatively constant in the pH range 6.5 to 9.5. Switching off the light, cytochrome c~2~ is reduced in Rb. sphaeroides chromatophores, with the maximum rate at pH 7.3 – 7.6. The data obtained suggest that cytochrome c~2~ reduction by ubiquinol in purple bacteria is accomplished by cytochrome bc~1~ complex. In proteoliposomes and soluble systems, this process depends on a direct nonenzymatic reaction.