| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2003: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2002: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Research Abstract |
The photochemical reaction center (RC) complex of Roseiflexus (R) castenholzii, which belongs to filamentous anoxygenic phototrophic bacteria (green filamentous bacteria) but lacks chlorosomes was isolated and characterized. The genes coding for the subunits of RC and the light-harvesting proteins were also cloned and sequenced. The RC complex was composed of L, M and cytochrome subunits. The cytochrome subunit showed a molecular mass of approximately 35 kDa, contained hemes c, and worked as the electron donor to the photooxidized special pair of bacteriochlorophyll (BChl) in the RC. The RC complex appeared to contain three molecules of BChl and three molecules of bacteriopheophytin (BPhe) as in the RC preparation from chloroflexus (Cfl) aurantiacus. The phylogenetic trees based on the deduced amino acid sequences of the RC subunits suggested that R.castenholzii had diverged from Cfl.aurantiacus very early after the divergence of filamentous anoxygenic phototrophic bacteria from purple bacteria. Although R.castenholzii is phylogenetically related to Cfl.aurantiacus, the arrangement of its puf genes, which code for the light-harvesting and the RC subunits, was different from that of Cfl.aurantiacus and similar to those in purple bacteria in the order of puf B, -A, -L, -M, and -C. Since the photosynthetic apparatus and genes of R.castenholzii have intermediary characteristics between purple bacteria and Cfl.aurantiacus, it is likely that they retain many features of the common ancestor of purple bacteria and filamentous anoxygenic phototrophic bacteria.
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