| Abstract: | The distribution of the fructose carrier over the membranes of Rhodopseudomonas sphaeroides was studied in cells grown under light saturation and light limitation. Three types of membranes were isolated after disruption of the cells in a French press. All three types were present in the cells grown either under the high or low light intensity, but they were present in different quantities. The cytoplasmic membrane could be separated from the photosynthetic membranes by Sephacryl S-1000 chromatography. The cytoplasmic membrane has the highest specific density and fructose carrier content and does not contain the light-harvesting pigments. The photosynthetic membranes could be resolved into two types by sucrose density gradient centrifugation. Type A predominates when cells are grown under light saturation, whereas type B, the chromatophores, is synthesized abundantly under light limitation. The properties of type A are in between the properties of the cytoplasmic membrane and the chromatophores. It has a slightly lower specific density and contains four times less fructose carrier than the cytoplasmic membrane, but contains half of the light-harvesting bacteriochlorophyll of the chromatophore membrane. The fructose carrier content in the type B membranes, the chromatophores, is very low. |
