Carotenoid Profiles in Pigment-Protein Complexes of Rhodospirillum rubrum
Schwerzmann, Rosmarie Ursula ; Bachofen, Reinhard
In: Plant and Cell Physiology, 1989, vol. 30, no. 4, p. 497-504
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- Young cells of Rhodospirillum rubrum contain a set of carotenoids from lycopene to spirilloxanthin. During growth, intermediates are almost completely converted to spirilloxan-thin. The ratio of the different carotenoid precursors vs. spirilloxanthin found in material of a certain age is the same in cells, chromatophores, light-harvesting complexes and reaction centers. Independent of the carotenoid composition and the age of the cells, the same detergent treatment can be used for isolation of pigment-protein complexes. Light-harvesting complexes of young cells containing mainly precursors of spirilloxanthin, as well as those of old cells in which spirilloxanthin dominates, both have their absorption maximum at 880 nm. It is thus assumed that all carotenoids of the spirilloxanthin series interact with bacteriochlorophyll a similarly to spirilloxanthin itself. From these results it is concluded that the micro-environment of these membrane-complexes is not influenced by the type of carotenoid present and that the assembly of the pigment-protein complexes in a growing membrane takes place before carotenoid biosynthesis has lead to the final product