Reaction center light harvesting B875 complexes from Rhodocyclus gelatinosus: characterization and identification of quinones.

Reaction center-B875 pigment-protein complexes were purified from Rhodocyclus gelatinosus. The proteic components consist of 7-8 polypeptides among which some were identified by their apparent molecular weights: the light harvesting B875 polypeptides α and β of 8 and 6 kDa, reaction center L (23 kDa), M (28 kDa) and H (34 kDa), cytochrome c (43 kDa). Four c-type hemes were found per reaction center. Flash-induced absorbance changes showed the presence of both QA and QB in the complex. Charge recombination times were determined to be: 1.16±0.2 (n=30) for P(+)QAQB (-) and 7-10 ms for P(+)QA (-) in presence of herbicides. From quinone analysis on one hand and kinetics of charge recombination on the other hand, we proposed that in the reaction center of Rhodocyclus gelatinosus QA is menaquinone 8 and QB is ubiquinone 8.