Preparation of a Photoactive Reaction Center Complex Containing Photo-reducible Fe-S Centers and Photooxidizable Cytochrome c from the Green Sulfur Bacterium Chlorobium tepidum |
| |
Authors: | Kusumoto Noriaki; Inoue Kazuhito; Nasu Hidekazu; Sakurai Hidehiro |
| |
Institution: | 1Department of Biology, School of Education, Waseda University Tokyo, 169-50 Japan
2Department of Biological Sciences, Faculty of Science, Kanagawa University 2946 Tsuchiya, Hiratsuka, Kanagawa, 259-12 Japan |
| |
Abstract: | A photoactive reaction center (RC) complex was isolated fromthe green sulfur bacterium Chlorobium tepidum by solubilizationof membranes with Triton X-100, followed by sucrosedensity gradientcentrifugation, DEAE Bio-Gel A chromatography, and hydroxyapatitechromatography. The purified RC complex contained about 5070bacteriochlorophyll molecules (BChl) per P840, as assayed byphotooxidafion. It showed a near-infrared BChl a absorptionpeak at 814 nm and shoulders at about 800 and 835 nm at roomtemperature. SDS-PAGE analysis revealed 6 polypeptides withapparent molecular masses of 100, 65, 41, 32, 23, and 18 kDa.The RC complex binds functional P840 and Cyt c551, which werephotooxidized by continuous illumination at room temperature.Upon flash excitation, the bound Cyt c551 was oxidized, andrereduced in the dark with a half-time of 16 and 400 ms in thepresence and absence of 0.1 mM 2,6-dichlorophenol indophenol,respectively, at room temperature. At 551 nm, the amount ofthe Cyt c photooxidized by continuous illumination was 60% ofthe amount determined by chemical oxidation-reduction. The functionalCyt c551/P840 ratio was calculated to be 1.21.7. EPRspectroscopy at cryogenic temperatures revealed that the RCcomplex binds three photoreducible Fe-S centers designated tobe CFA, CFB and CFX (C for Chlorobium). CFA and CFB were reducedin the dark with dithionite at pH 10. (Received May 26, 1993; Accepted October 4, 1993) |
| |
Keywords: | |
本文献已被 Oxford 等数据库收录! |
|