Comparison of Structural Subunits of the Core Light-Harvesting Complexes of Photosynthetic Bacteria

The photoreceptor complex (PRC) of photosynthetic bacteria consists of a reaction center (RC) and one or more light-harvesting (LH) complexes. All bacteria seem to have a core LH complex which is biosynthesized in constant proportion to the RC and coded for by genes that are adjacent to those for the L and M polypeptides of the RC (1–3). Among the more simple bacteria, Rhodospirillum rubrum contains only the core LH complex which has been named B881 for wildtype R. rubrum, or B873 for its car- G-9 mutant after the γmax of the red-most absorbance band (Qy band) in the organism.