Abstract
Cells of Rhv. sulfidophilum were grown under different conditions in the presence of 32P-phosphate and the corresponding H and L membrane fractions obtained and fractionated by SDS-PAGE. Both membranes showed almost identical polypeptide composition. The bacteriochlorophyll (Bchl) specific content in H was always lower that in L. As described before, oxygen did not regulate gene expression. Under high light, an almost two- to threefold decrease of the cellular specific Bchl content was observed. Pulse and chase experiments showed that transitions from aerobiosis to light-anaerobiosis did not quantitatively affect the Bchl content of the membranes, although a turnover of the 32P-phosphate and 35S-methionine was observed. LHI β was the only polypeptidic subunit of the Bchl-binding polypeptides that was phosphorylated in vivo, and phosphotyrosine was the only phosphorylated amino acid detectable. The phosphorylated LHI β was determined to be insoluble in the organic solvent mixture of (vol/vol) 1:1 chloroform-methanol containing ammonium acetate (0.1 m final concentration). Treatment with a chaotropic agent such as Na2CO3 solubilized the phosphorylated LHI β, indicating that part of this posttranslationally modified polypeptide was not inserted in a transmembrane position. These results were used to speculate about the regulatory properties of this posttranslational modification of LHI β on membrane differentiation.
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Received: 30 August 2000 / Accepted: 2 October 2000
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Iustman, L., Pucheu, N., Kerber, N. et al. Phosphorylation of LHI β During Membrane Synthesis in the Photosynthetic Bacterium Rhodovulum sulfidophilum . Curr Microbiol 42, 323–329 (2001). https://doi.org/10.1007/s002840010224
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DOI: https://doi.org/10.1007/s002840010224