Bioenergetics Studies of the Cyanobacterium Anabaena variabilis

1987 ◽  
Vol 42 (11-12) ◽  
pp. 1280-1284 ◽  
Author(s):  
Siegfried Scherer ◽  
Heike Sadowski ◽  
Peter Böger
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Cytochrome B ◽  
Anabaena Variabilis ◽  
Electron Donors ◽  
Free System ◽  
Low Concentrations ◽  
Cyanobacterium Anabaena ◽  
A Cell ◽  
C Complex

A cell-free system exhibiting both photophosphorylation (P/2e= 1) and oxidative phosphoryltion (P/O up to 0.8) is described for the cyanobacterium Anabaena variabilis. NADH ant NADPH were found to be equally effective as electron donors for oxidative phosphorylation. Low concentrations of UHDBT, an inhibitor of the cytochrome b/c complex of mitochondria ant loroplasts, were found to inhibit photosystem-II electron transport reactions, but did not affet the cytochrome b6/f-complex of Anabaena. The inhibition by myxothiazol, antimycin and heptyihydroxyquinoline corroborates the hypothesis that both respiration and photosynthesis share the cytochrome b6/f-complex.

scholarly journals Proton translocation by the mitochondrial cytochrome b-c1 complex is inhibited by NN′-dicyclohexylcarbodi-imide

1982 ◽  
Vol 206 (2) ◽  
pp. 419-421 ◽  
Author(s):  
B D Price ◽  
M D Brand
Keyword(s):  
Electron Transport ◽  
Cytochrome Oxidase ◽  
Cytochrome B ◽  
Rat Liver ◽  
Proton Translocation ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Mitochondrial Cytochrome ◽  
Low Concentrations ◽  
Mitochondrial Cytochrome B

NN'-Dicyclohexylcarbodi-imide at low concentrations decreases the H+/2e ratio for rat liver mitochondria over the span succinate to oxygen from 5.9 +/- 0.3 (mean +/- S.E.M.) to 4.0 +/- 0.1 and for the cytochrome b-c1 complex from 3.8 +/- 0.2 to 1.9 +/- 0.1, but has little effect on the H+/2e ratio of cytochrome oxidase. The decrease in stoicheiometry is due, not to uncoupling or inhibition of electron transport, but to inhibition of proton translocation. NN'-Dicyclohexylcarbodi-imide thus ‘decouples’ proton translocation in the cytochrome b-c1 complex.

Inhibition by Tetranitromethane of Photosynthetic Electron Transport from Water to Photosystem II in Chloroplasts

1980 ◽  
Vol 35 (3-4) ◽  
pp. 293-297 ◽  
Author(s):  
P. V. Sane ◽  
Udo Johanningmeier
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Electron Flow ◽  
Ph Dependence ◽  
Photosynthetic Electron Transport ◽  
Donor Side ◽  
Ps Ii ◽  
Diphenyl Carbazide ◽  
Low Concentrations ◽  
Sh Group

Abstract Low concentrations (10 µM) of tetranitromethane inhibit noncyclic electron transport in spinach chloroplasts. A study of different partial electron transport reactions shows that tetranitromethane primarily interferes with the electron flow from water to PS II. At higher concentrations the oxidation of plastohydroquinone is also inhibited. Because diphenyl carbazide but not Mn2+ ions can donate electrons efficiently to PS II in the presence of tetranitromethane it is suggested that it blocks the donor side of PS II prior to donation of electrons by diphenyl carbazide. The pH dependence of the inhibition by this protein modifying reagent may indicate that a functional-SH group is essential for a protein, which mediates electron transport between the water splitting complex and the reaction center of PS II.

The interaction of polymeric viologens with hydrogenases from Desulfovibrio desulfuricans and Clostridium pasteurianum

1979 ◽  
Vol 57 (8) ◽  
pp. 1093-1098 ◽  
Author(s):  
Bernard R. Glick ◽  
William G. Martin ◽  
J. Jean Giroux ◽  
Ross E. Williams
Keyword(s):  
Hydrogen Production ◽  
Methyl Viologen ◽  
Desulfovibrio Desulfuricans ◽  
Electron Donors ◽  
Clostridium Pasteurianum ◽  
Maximal Rate ◽  
Free System ◽  
Electrophoretic Band ◽  
Cell Free System ◽  
A Cell

The interaction between hydrogenases from either Desulfovibrio desulfuricans or Clostridium pasteurianum and electron donors methyl viologen or polymeric viologens was examined. Extracts from each organism contained a single gel electrophoretic band of active hydrogenase. The hydrogenase of D. desulfuricans was much more stable than that of Cl. pasteurianum. With methyl viologen apparent Km and Vm values were 0.5 mM and 0.62 μmol H2/min per milligram protein for the Cl. pasteurianum and 0.7 and 6.2 μmol H2/min per milligram protein, respectively, for the D. desulfuricans enzyme. The hydrogenases bound the polymeric viologens more tightly than methyl viologen, more so for the enzyme of D. desulfuricans than for Cl. pasteurianum. Maximal rate of hydrogen production was less with the polymeric than with methyl viologen. The results suggest that the D. desulfuricans enzyme in conjunction with a polymeric viologen may perform better in a cell-free system aimed at hydrogen production than that from Cl. pasteurianum.

Photosynthetic components and activities of nitrogen-fixing isolated heterocysts of Anabaena cylindrica

1977 ◽  
Vol 198 (1130) ◽  
pp. 61-86 ◽  
Keyword(s):  
Electron Transport ◽  
Photosystem Ii ◽  
Cytochrome B ◽  
Nitrogenase Activity ◽  
Photosynthetic Electron Transport ◽  
Central Component ◽  
Reaction Centre ◽  
Anabaena Cylindrica ◽  
Higher Plant ◽  
Transport Chain

Isolated heterocysts of the N 2 -fixing Anabaena cylindrica , prepared by a combination of lysozyme and Yeda press treatments, are metabolically active with over 90% of the measurable nitrogenase activity being located in the heterocyst preparations after disruption of the intact filaments. The photosynthetic activities of such isolated heterocysts are characterized by an inability to carry out the photolysis of water or to fix CO 2 . The lack of O 2 evolution appears to be due in part to the deple­tion during heterocyst differentiation of Mn, a central component of the photosystem II reaction centre in O 2 -evolving algae. There is evidence that components of the photosynthetic electron transport chain on the reducing side of the photosystem II reaction centre are present and functional in heterocysts. These include cytochrome c 554 , plastocyanin, plastoquinone, cytochrome b 559 , P700, cytochrome b 563 , and iron-sulphur proteins which appear to correspond to centre A and centre B of higher plant chloroplasts. Soluble, or loosely bound ferredoxin is also present and involved in electron transport from ferredoxin to NADP. Isolated heterocysts photoreduce methylviologen when reduced 2,6-dichlorophenolindophenol and diphenylcarbazide serve as electron donors. They show P700 photo-oxidation and photoreduction, photosyn­thetic electron transport which is inhibited by 2,5-dibromo-3-methyl-6-isopropyl- p -benzoquinone an antagonist of plastoquinone, photophos­phorylation, oxidative phosphorylation and ferredoxin-NADP oxido-reductase mediated reactions. The photosynthetic modifications of the heterocyst are such that electron transport and the generation of ATP for nitrogenase can occur without concomitant O 2 evolution and with­out nitrogenase having to compete with CO 2 fixation for ATP and reductant.

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