Isolation and characterization of the B798 light-harvesting baseplate from the chlorosomes of Chloroflexus aurantiacus.
The B798 light-harvesting baseplate of the chlorosome antenna complex of the thermophilic, filamentous anoxygenic phototrophic bacterium Chloroflexus aurantiacus has been isolated and characterized. Isolation was performed by using a hexanol-detergent treatment of freeze-thawed chlorosomes. The isolated baseplate consists of Bchl a, beta-carotene, and the 5.7 kDa CsmA protein with a ratio of 1.0 CsmA protein/1.6 Bchl a/4.2 beta-carotenes. The baseplate has characteristic absorbance at 798 nm as well as carotenoid absorbance maxima at 519, 489, and 462 nm. The energy transfer efficiency from the carotenoids to the Bchl a is 30% as measured by steady-state and ultrafast time-resolved fluorescence and absorption spectroscopies. Energy equilibration within the Bchl a absorbing regions exhibits ultrafast kinetics. Circular dichroism spectroscopy shows no evidence for excitonically coupled Bchl a pools within the 798 nm region.
Montaño
Gabriel A
GA
Graduate Program in Molecular and Cellular Biology, Arizona State University, Tempe, Arizona 85287-1604, USA.
Wu
Hsing-Mei
HM
Lin
Su
S
Brune
Daniel C
DC
Blankenship
Robert E
RE
D001426:Bacterial Proteins / Q000737:chemistry / Q000302:isolation & purification; D001429:Bacteriochlorophylls / Q000737:chemistry / Q000302:isolation & purification; D019414:Chlorobi / Q000737:chemistry*; D002875:Chromosomes / Q000737:chemistry*; D004591:Electrophoresis, Polyacrylamide Gel; D004735:Energy Transfer; D007700:Kinetics; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000302:isolation & purification*; D013057:Spectrum Analysis / Q000379:methods; D019207:beta Carotene / Q000737:chemistry / Q000302:isolation & purification
D001426:Bacterial Proteins; D001429:Bacteriochlorophylls; C086532:CsmM protein, Chloroflexus aurantiacus; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D019207:beta Carotene