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'Cyanobacterium' in keywords Facet   Publication Year 1995  [X]
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1995[X]
1Author    KlausP. Bader, Anja RöbenRequires cookie*
 Title    Mass Spectrometric Detection and Analysis of Nitrogen Fixation in Oscillatoria chalybea  
 Abstract    By means of mass spectroscopic m easurements in an artifical gas atmosphere containing the stable nitrogen isotope 15N2 we were able to demonstrate nitrogen fixation capacity in the filamentous cyanobacterium Oscillatoria chalybea. Our technique proved to be well-suited also for investigations on the light-induced nitrogen fixation in the purple bacteria Rhodobacter sphaeroides and Rhodobacter capsulatus. Oscillatoria chalybea grown without combined nitrogen showed a substantial 15N2-uptake which could clearly be correlated with nitrogen fixation. Nitrate grown cultures did not show this nitrogen uptake or only to a minimal extent. Addition of ammonium chloride resulted in a rapid deactivation of the nitro-genase system. Similar observations have been made with other so-called switch-off effectors like phenazine methosulfate. The structural integrity of the filaments appeared to be a pre­ requisite for nitrogen fixation also in this organism, as even mild mechanical homogenization strongly inhibited the N2-uptake signals. Illumination of the assays under conditions where the photooxidition of water is not operational (Bader, K. P. (1994), Biochim. Biophys. A cta 1188, 2 1 3 -2 1 9) did not affect the nitrogen fixation in Oscillatoria chalybea. Illumination of cultures with concom itant release of oxygen from the w ater splitting reaction resulted in strong inhibition of 15N2-uptake. 
  Reference    Z. Naturforsch. 50c, 199 (1995); received November 11 1994/January 30 1995 
  Published    1995 
  Keywords    Mass Spectrometry, Nitrogen Fixation, Photosynthesis, Cyanobacterium 
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 TEI-XML for    default:Reihe_C/50/ZNC-1995-50c-0199.pdf 
 Identifier    ZNC-1995-50c-0199 
 Volume    50 
2Author    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