Chimeric photosynthetic reaction center complex of purple bacteria composed of the core subunits of Rubrivivax gelatinosus and the cytochrome subunit of Blastochloris viridis

A gene coding for the photosynthetic reaction center-bound cytochrome subunit, pufC, of Blastochloris viridis, which belongs to the alpha-purple bacteria, was introduced into Rubrivivax gelatinosus, which belongs to the beta-purple bacteria. The cytochrome subunit of B. viridis was synthesized in the R. gelatinosus cells, in which the native pufC gene was knocked out, and formed a chimeric reaction center (RC) complex together with other subunits of R. gelatinosus. The transformant was able to grow photosynthetically. Rapid photo-oxidization of the hemes in the cytochrome subunit was observed in the membrane of the transformant. The soluble electron carrier, cytochrome c(2), isolated from B. viridis was a good electron donor to the chimeric RC. The redox midpoint potentials and the redox difference spectra of four hemes in the cytochrome subunit of the chimeric RC were almost identical with those in the B. viridis RC. The cytochrome subunit of B. viridis seems to retain its structure and function in the R. gelatinosus cell. The chimeric RC and its mutagenesis system should be useful for further studies about the cytochrome subunit of B. viridis.