Redox effects on the bacteriochlorophyll a-containing Fenna-Matthews-Olson protein from Chlorobium tepidum.
The BChl a-containing Fenna-Matthews-Olson (FMO) protein from the green sulfur bacterium Chlorobium tepidum was purified and characterized. Fluorescence spectra indicate that efficient excited state quenching occurs at neutral or oxidizing redox potentials. The major fluorescence lifetime at room temperature is approximately 60 ps in samples that are in neutral or oxidizing conditions, and approximately 2 ns in samples where the strong reductant sodium dithionite has been added. A similar change is observed in pump-probe picosecond absorbance difference experiments, where the long life time component increases after dithionite addition. A 16 Gauss wide EPR signal with g factor = 2.005 is observed in samples without dithionite. This signal largely disappears upon addition of dithionite. Dithionite induces large reversible changes in the 77 K absorbance spectra of the purified FMO protein and in whole cells. These results indicate that the FMO protein contains redox active groups, which may be involved in the regulation of energy transfer. Room temperature circular dichroism and low temperature absorption spectra show that dithionite also induces conformational or structural changes of the FMO protein complex.
Zhou
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Department of Chemistry and Biochemistry, Arizona State University, Tempe 85287-1604, USA.
LoBrutto
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Lin
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Blankenship
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D001426:Bacterial Proteins / Q000737:chemistry / Q000187:drug effects / Q000302:isolation & purification; D001429:Bacteriochlorophylls / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D019414:Chlorobi / Q000737:chemistry* / Q000378:metabolism*; D004227:Dithionite / Q000494:pharmacology; D004579:Electron Transport; D004735:Energy Transfer; D045342:Light-Harvesting Protein Complexes; D010084:Oxidation-Reduction; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000187:drug effects / Q000302:isolation & purification* / Q000378:metabolism; D013050:Spectrometry, Fluorescence
D001426:Bacterial Proteins; D001429:Bacteriochlorophylls; C086320:FMO bacteriochlorophyll protein, Bacteria; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D004227:Dithionite