May 5, 1992

Photosynthetic electron-transfer reactions in the green sulfur bacterium Chlorobium vibrioforme: evidence for the functional involvement of iron-sulfur redox centers on the acceptor side of the reaction center

Biochemistry
M MillerJ Biggins

Abstract

The green sulfur bacterium Chlorobium vibrioforme was cultured in the presence of ethylene to selectively inhibit the synthesis of the chlorosome antenna BChl d. Use of these cells as starting material simplified the isolation of a photoactive antenna-depleted membrane fraction without the use of high concentrations of detergents. The preparation had a BChl alpha/P840 of 50, and the spectral properties were similar to those of preparations isolated from cells grown with a normal complement of chlorosomes. The membrane preparation was active in NADP+ photoreduction. This indicated that the fraction contained reaction centers with complete electron-transfer sequences which were then characterized further by flash kinetic spectrophotometry and EPR. We confirmed that cytochrome c553 is the endogenous donor to P840+, and at room temperature we observed a recombination reaction between the reduced terminal acceptor and P840+ with a t1/2 = 7 ms. Oxidative degradation of iron-sulfur centers using low concentrations of chaotropic salts introduced a faster recombination reaction of t1/2 = 50 microseconds which was lost at higher concentrations of chaotrope, indicating the participation of another iron-sulfur redox center earlier than the...Continue Reading

Mentioned in this Paper

Spectrophotometry
NADP
Oxidation-Reduction
Photosynthetic Reaction Center Complex Proteins
Iron-Sulfur Proteins
Dark Reactions of Photosynthesis
Respiratory Chain
Plasma Membrane

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