Association of LHIα(B870) Polypeptide with Phospholipids During Insertion in the Photosynthetic Membrane of an LHII? Mutant of Rhodobacter capsulatus |
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Authors: | Norma L Pucheu Norma L Kerber Emilio A Rivas Néstor Cortez Augusto F Garcia |
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Institution: | (1) Universidad de Buenos Aires, Facultad de Agronomía, Cátedra de Microbiología y Centro de Investigaciones Bioquímicas y Fisiológicas (CIBYF-CONICET), Av. San Martín 4453, 1417 Buenos Aires, Argentina , AR;(2) Universidad de Buenos Aires, Facultad de Medicina, Instituto de Biología Celular y Neurociencias, Paraguay 2155, 1121 Buenos Aires, Argentina , AR;(3) Universidad Nacional de Rosario, Facultad de Ciencias Bioquímicas y Farmacéuticas, Programa Multidisciplinario de Biología Experimental (PROMUBIE), Suipacha 531, 2000 Rosario, Santa Fe, Argentina , AR |
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Abstract: | Membranes from in vivo labeled cells of Rhodobacter
capsulatus U43pTX35] grown photosynthetically carried 60% of
the 32P]-Pi in the “heavy” fraction (HM) after
sucrose gradient sedimentation. Metal-chelating chromatography of either
“heavy” or “light” (LM) membrane fractions rendered
similar Bchl-protein complex profiles after octyl-glucoside treatment,
including most of the radioactivity in the same corresponding elution
fraction (F II). Similar labeling distribution of pigment-protein complexes
was obtained for membranes of dark-grown cells induced by lowering oxygen
tension. Fractions derived from HM showed highly labeled LHIα, whereas the
same complex from LM was essentially 32P]-Pi-free, as revealed
by SDS-PAGE followed by autoradiography. Phospholipid analysis showed a
similar pattern for membranes isolated from cells photosynthetically or
semiaerobically grown, being the most abundant: phosphatidylglycerol,
phosphatidylethanolamine, cardiolipin, and phosphatidylcholine. Part of the
phospholipids from HM comigrated with LHIα during SDS-PAGE and dissociated
from the complexes only after solvent extraction and hydrophobic
chromatography. However, a small amount remained always attached to LHIα,
indicating an unusual strong interaction. These results suggest the existence
of two operationally defined membrane regions carrying LHIα complexes
differing in phosphorylation status and protein-phospholipid interaction.
Received: 10 August 1996 / Accepted: 10 September 1996 |
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