Modifiable chromatophore proteins in photosynthetic bacteria

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Abstract
The chromatophores of Chromatium vinosum, and 6 other photosynthetic bacteria, contained 2 or more proteins which were insoluble when heated in the presence of sodium dodecyl sulfate (SDS) and 2-mercaptoethanol (.beta.-ME). When the chromatophores were dissolved at room temperature in SDS-.beta.-ME, these proteins were present in the SDS-polyacrylamide gel electrophoresis profiles but when the samples were dissolved at 100.degree. C, they were absent or considerably diminished. When 1-dimensional gels of chromatophores solubilized at room temperature were soaked in the SDS-.beta.-ME solution and heated to 100.degree. C and the gels were run in a 2nd dimension, the proteins became immobilized in the original 1st-dimension gel, where they could be detected by staining. The 2 major proteins so affected in C. vinosum had apparent MW of 28,000 and 21,000. The chromatophores of several other photosynthetic bacteria also contained predominant proteins between 30,000 and 19,000 MW, which became insoluble when heated in the presence of SDS and .beta.-ME. In at least 2 of the species, these appeared to be reaction center proteins. The conditions causing the proteins to become insoluble were complex and involved temperature, SDS concentration and the presence of SH reagents. The chromatophores of 4 spp. of Chromatiaceae and 2 strains of 1 sp. of Rhodospirillaceae had a protein-pigment complex that was visible in SDS-polyacrylamide gel profiles of samples dissolved at room temperature but was absent in samples dissolved at 100.degree. C.