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1994 (1)
1993 (1)
1Author    JohnN. Phillips, WendyK. BanhamRequires cookie*
 Title    Hydrogen Bonding of Cyanoacrylates with the D 1 Peptide  
 Abstract    Representatives o f two structural types o f cyanoacrylate PS II inhibitors have been studied in respect to their p/ 50 values and qualitative rate o f binding with wild type and S 2 6 4 G mutant thylakoids isolated from Brassica napus. Both are potent inhibitors o f photosynthetic electron transport and both show a large discrimination between wild type and mutant thylakoids under equilibrium conditions. However one, an N-m ethylanilino cyanoacrylate, has an initial rapid reaction with both wild type and mutant thylakoids, but continues to react slowly with the wild type species until equilibrium is reached, while the other, a benzylamino cyanoacry­ late, equilibrates rapidly with both species as does the classical PS II inhibitor, atrazine. These differences in kinetic behaviour have been interpreted in terms o f different H-bond interac­ tions with the serine-264 hydroxyl group. It is suggested that the slow binding reaction is due to the N -m ethylanilino com pound interacting as an H-bond acceptor with the serine-264 hy­ droxyl hydrogen thus disrupting an intramolecular ser-264-his-252 H-bond within the D 1 peptide. Rapid equilibration on the other hand, has been attributed to the benzylam ino deriva­ tive acting as an H-bond donor to the serine-264 hydroxyl oxygen and strengthening the 2 6 4 -2 5 2 H -bond by conjugation. It is proposed that atrazine and other classical PS II inhibi­ tors act in this way and that this may explain their ability to inhibit trypsin degradation o f the D 1 peptide, if the 2 6 4 -2 5 2 intramolecular H-bond plays an important role in stabilizing the peptide conform ation. It is also speculated that photodegradation may be related to the ability o f Q b~ to act as an H-bond acceptor and disrupt the 2 6 4 -2 5 2 H-bond. 
  Reference    Z. Naturforsch. 48c, 132 (1993); received N ovem ber 16 1992 
  Published    1993 
  Keywords    Brassica napus, Cyanoacrylates, D 1 Peptide, H -Bonding, Photodegradation 
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 TEI-XML for    default:Reihe_C/48/ZNC-1993-48c-0132.pdf 
 Identifier    ZNC-1993-48c-0132 
 Volume    48 
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