Assembly and structural organization of pigment-protein complexes in membranes of Rhodopseudomonas sphaeroides.
The B875 and B800-850 light-harvesting pigment-protein complexes of Rhodopseudomonas sphaeroides are characterized further by lithium dodecyl sulfate/polyacrylamide gel electrophoresis at 4 degrees C. Bacteriochlorophyll a was shown in reconstruction studies to remain complexed with its respective binding proteins during this procedure. From distributions in these gels, a quantitative description for the arrangement of the complexes is proposed. Assembly of the complexes was examined in delta-aminolevulinate-requiring mutant H-5 after a shift from high- to low-light intensity. After 10 h of delta-[3H]aminolevulinate labeling, the specific radioactivity of bacteriochlorophyll in a fraction containing putative membrane invaginations reached the maximal level, while that of the mature photosynthetic membrane was at only one-third this level. This suggests that membrane invaginations are sites of preferential bacteriochlorophyll synthesis in which completed pigment-proteins exist transiently. Analysis of the 3H distribution after electrophoretic separation further suggests that photosynthetic membranes grow mainly by addition of B800-850 to preformed membrane consisting largely of B875 and photochemical reaction centers. These results corroborate the above model for the structural organization of the light-harvesting system and indicate that the structurally and functionally discrete B800-850 pool is not completely assembled until all B875 sites for B800-850 interactions are occupied.
D000622:Aminolevulinic Acid / Q000378:metabolism; D020130:Bacterial Chromatophores / Q000378:metabolism; D001426:Bacterial Proteins / Q000302:isolation & purification / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D007700:Kinetics; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D012242:Rhodobacter sphaeroides / Q000378:metabolism*; D014316:Tritium
D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D014316:Tritium; D000622:Aminolevulinic Acid