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Phosphorylation of LHI β during membrane synthesis in the photosynthetic bacterium Rhodovulum sulfidophilum
Iustman, L.J.R.; Pucheu, N.L.; Kerber, N.L.; Vandekerckhove, J.; Tadros, M.H.; Garcia, A.F. (2001). Phosphorylation of LHI β during membrane synthesis in the photosynthetic bacterium Rhodovulum sulfidophilum. Curr. Microbiol. 42(5): 323-329. dx.doi.org/10.1007/s002840010224
In: Current Microbiology. Springer-Verlag: New York. ISSN 0343-8651, more
Peer reviewed article  

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Keyword
    Marine

Authors  Top 
  • Iustman, L.J.R.
  • Pucheu, N.L.
  • Kerber, N.L.
  • Vandekerckhove, J.
  • Tadros, M.H.
  • Garcia, A.F.

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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