Regulation of Photosynthetic Unit Structure in Rhodospirillum Rubrum Whole Cells

The photosynthetic unit (PSU) in Rhodospirillum rubrum consists of a reaction center (RC) which is about 95 kd (Gingras, 1978) and a light-harvesting (LH) antenna complex which has a molecular weight of about 150 kd (Picorel et al., 1983). The RC contains 3 polypeptides, 4 bacteriochlorophyll, 2 bacteriopheophytin and severalubiquinone molecules. The LH complex contains 21±3 bacteriochlorophyll, 10±2 carotenoid and 9 to 12 copies of each of two small polypeptides. Thus, the total size of this fundamental unit is about 250 kd.