ASSOCIATION OF LHI-ALPHA(B870) POLYPEPTIDE WITH PHOSPHOLIPIDS DURING INSERTION IN THE PHOTOSYNTHETIC MEMBRANE OF AN LHII(-) MUTANT OF RHODOBACTER-CAPSULATUS
Nl. Pucheu et al., ASSOCIATION OF LHI-ALPHA(B870) POLYPEPTIDE WITH PHOSPHOLIPIDS DURING INSERTION IN THE PHOTOSYNTHETIC MEMBRANE OF AN LHII(-) MUTANT OF RHODOBACTER-CAPSULATUS, Current microbiology, 34(3), 1997, pp. 155-161
Membranes from in vivo labeled cells of Rhodobacter capsulatus U43[pTX
35] grown photosynthetically carried 60% of the [P-32]-Pi in the ''hea
vy'' fraction (HM) after sucrose gradient sedimentation, Metal-chelati
ng chromatography of either ''heavy'' or ''Light'' (LM) membrane fract
ions rendered similar Bchl-protein complex profiles after octyl-glucos
ide treatment, including most of the radioactivity in the same corresp
onding elution fraction (F II). Similar labeling distribution of pigme
nt-protein complexes was obtained for membranes of dark-grown cells in
duced by lowering oxygen tension. Fractions derived from HM showed hig
hly labeled LHI alpha, whereas the same complex from LM was essentiall
y [P-32]-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 mos
t abundant: phosphatidyl glycerol, phosphatidylethanolamine, cardiolip
in, and phosphatidyl-choline. Part of the phospholipids from HM comigr
ated with LHI alpha during SDS-PAGE and dissociated from the complexes
only after solvent extraction and hydrophobic chromatography, However
, a small amount remained always attached to LHI alpha, indicating an
unusual strong interaction. These results suggest the existence of two
operationally defined membrane regions carrying LHI alpha complexes d
iffering in phosphorylation status and protein-phospholipid interactio
n.