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pH‐Abhängigkeit der Cytochrom c 2 ( c )‐Reduktion und des Membranpotentials (Δ Ψ) in Modellsystemen und Chromatophoren von Purpurbakterien
Author(s) -
Oleskin Alexander V.,
Samullov Vitaly D.
Publication year - 1992
Publication title -
journal of basic microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.58
H-Index - 54
eISSN - 1521-4028
pISSN - 0233-111X
DOI - 10.1002/jobm.3620320608
Subject(s) - ubiquinol , chemistry , rhodobacter sphaeroides , rhodospirillum rubrum , cytochrome , cytochrome c , antimycin a , coenzyme q – cytochrome c reductase , photochemistry , photosynthetic reaction centre , cytochrome c1 , reaction rate constant , stereochemistry , electron transport chain , kinetics , electron transfer , biochemistry , photosynthesis , mitochondrion , enzyme , physics , quantum mechanics
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.