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1995 (1)
1994 (1)
1Author    O. Kruse, G. H. SchmidRequires cookie*
 Title    The Role of Phosphatidylglycerol as a Functional Effector and Membrane Anchor of the D l-C ore Peptide from Photosystem II-Particles of the Cyanobacterium Oscillatoria chalybea  
 Abstract    The intrinsic polypeptide D l, isolated from photosystem (PS) Il-particles of the cyanobac­ terium Oscillatoria chalybea, was obtained by electroelution and fractionated extraction with organic solvents. Purification was demonstrated by Western blotting and amino acid sequenc­ ing. By carrying out D1 -immunization in rabbits a polyclonal monospecific D1-antiserum was obtained. For the qualitative characterization of D1 as a lipid-binding peptide, the effect of the lipids phosphatidylglycerol (PG), monogalactosyldiacylglyceride (M G D G) and phosphatidylcho­ line (PC) on PSII-oxygen evolution was analysed in reconstitution experiments. In these experiments purified photosystem II (PSII)-particle preparations were treated with the en­ zyme phospholipase A 2 and supplemented with lipid emulsions. We were able to show that the inhibition of electron transport, as the consequence of this lipase treatment, was only relieved, if phosphatidylglycerol was added to the preparation. A model was proposed, in which phosphatidylglycerol is a functional effector for the optimal conformation of D 1 in the PSII core complex. Phosphatidylglycerol molecules are unusually tightly bound to the D1 peptide by hydrophobic interactions. A covalent binding seems not probable. The localisation of phosphatidylglycerol binding sites was found by trypsin treatment of D1 and analysis of the obtained oligopeptides with HPLC and immunoblotting. The binding sites could be con­ fined to the hydrophobic amino acid section between arginine 27 and arginine 225. which is known to be the membrane anchor of D l. This has led us to the conclusion that the phospho­ lipid phosphatidylglycerol plays an important role for anchoring the Dl-peptide and for its orientation in the thylakoid membrane. Phosphatidylglycerol with its high amount of palmitic acid has in prokaryotic cyanobacteria apparently a role in stabilization and orientation. The high turn-over of D l and the spatial separation of the synthesis-and incorporation-site in the membrane, developed during evolution in eukaryotic organisms, might have changed the requirement on the mobility and the orientation of D l in photosynthetic membranes. 
  Reference    Z. Naturforsch. 50c, 380—390 (1995); received December 12 1994/February 24 1995 
  Published    1995 
  Keywords    Dl-Peptide, Phosphatidylglycerol, Lipid-Protein Binding, Cyanobacterium, PSII-Complex 
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 TEI-XML for    default:Reihe_C/50/ZNC-1995-50c-0380.pdf 
 Identifier    ZNC-1995-50c-0380 
 Volume    50 
2Author    O. Kruse, A. Radunz, G. H. SchmidRequires cookie*
 Title    Phosphatidylglycerol and ß-Carotene Bound onto the D 1-Core Peptide of Photosystem II in the Filamentous Cyanobacterium Oscillatoria chalybea  
 Abstract    -particles from the cyanobacterium Oscillatoria chalybea were isolated by fractionating centrifugation. Purification of these particles was achieved by a 22 hours cen­ trifugation over a linear sucrose density gradient at 217.500 X g. The obtained particle frac­ tion exhibited an oxygen evolution activity which corresponded to three times the rate of intact cells and to five times the rate of intact thylakoids. The chlorophyll protein ratio was 1:10 and the ratio manganese/chlorophyll 1:34. SDS-polyacrylamide gel electrophoresis showed that the photosystem Il-fraction is com­ posed of the core peptides D 1 and D2, the chlorophyll-binding peptides CP 43 and CP 47, the extrinsic 33 kDa peptide (manganese stabilizing peptide, MSP) and phycobiliproteins with molecular masses between 16 to 20 kDa. Cyt b559 was not detected in our gel electro­ phoresis assay. Part of the peptides of the 30 kDa-region (D 1, D 2, MSP) occurred as aggre­ gates with a molecular mass of 60 to 66 kDa. The D 1-peptide was isolated from the PS Il-preparation by SDS-gel electrophoresis. The intrinisic peptide reacts in the Western blot procedure with the antiserum to phosphatidyl­ glycerol and with the antiserum to ß-carotene. Incubation of the peptide with the antisera to monogalactosyldiglyceride, sulfoquinovosyldiglyceride and zeaxanthine resulted negatively. The binding of phosphatidylglycerol onto the D 1-peptide was confirmed by lipid analysis in HPLC and fatty acid analysis by gas chromatography. Only this lipid, respectively the typi­ cal fatty acid mixture of this lipid was detected. The lipid is characterized by the fact that the hexadecenoic acid does not exhibit rraws-configuration, as is true for phosphatidylglycerol of higher plants and algae, but occurs in cw-configuration. With the antibody being directed towards the glycerol-phosphate residue and not towards the fatty acids, it can be concluded from the reaction of the antibodies with the bound lipid that the lipid is bound to the peptide via the fatty acid. The negatively charged phosphatidyl­ glycerol increases the hydrophobicity of the peptide and leads to a negatively charged sur­ face favouring binding of cations like calcium and magnesium. The fact that incubation of this PS Il-fraction with phospholipase inhibits photosynthetic activity by 25% which can be fully restored by addition of phosphatidylglycerol, shows that bound phosphatidylglycerol has a functional role. 
  Reference    Z. Naturforsch. 49c, 115—124 (1994); received July 16/October 181993 
  Published    1994 
  Keywords    D 1-Peptide, Phosphatidylglycerol, ß-Carotene, Antibody, Lipid-Protein Binding, Cyanobacterium, Manganese Stabilizing Peptide Photosystem II 
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 TEI-XML for    default:Reihe_C/49/ZNC-1994-49c-0115.pdf 
 Identifier    ZNC-1994-49c-0115 
 Volume    49