Localization of a site of energy coupling between plastoquinone and cytochrome f in the electron-transport chain of spinach chloroplasts

Biochemistry ◽  
1972 ◽  
Vol 11 (7) ◽  
pp. 1155-1160 ◽  
Author(s):  
H. Boehme ◽  
W. A. Cramer
Keyword(s):  
Electron Transport ◽  
Electron Transport Chain ◽  
Energy Coupling ◽  
Cytochrome F ◽  
Spinach Chloroplasts ◽  
Transport Chain ◽  
A Site

Localized energy coupling during photophosphorylation by chromatophores of Rhodopseudomonas capsulata N22

1982 ◽  
Vol 2 (10) ◽  
pp. 743-749 ◽  
Author(s):  
G. Duncan Hitchens ◽  
Douglas B. Kell
Keyword(s):  
Free Energy ◽  
Electron Transport ◽  
Atp Synthase ◽  
Electron Transport Chain ◽  
Energy Coupling ◽  
Rhodopseudomonas Capsulata ◽  
Titration Method ◽  
Dual Inhibitor ◽  
Transport Chain ◽  
Synthase Inhibitor

The principle of the dual inhibitor titration method for testing models of electron-transport phosphorylation is outlined, and the method is applied to the study of photophosphorylation in bacterial chromatophores. It is concluded that energy coupling is strictly localized in nature in this system, in the sense that free energy released by a particular electron-transport chain may be used only by a particular H+-ATP synthase. Dual inhibitor titrations using the uncoupler SF 6847 and the H+-ATP synthase inhibitor oligomycin indicate that uncouplers act by shuttling rapidly between the localized energy-coupling sites.

The Expression of Subunits of the Mitochondrial Complex I-Homologous NAD(P)H-Plastoquinone-Oxidoreductase during Plastid Development

1997 ◽  
Vol 52 (7-8) ◽  
pp. 481-486 ◽  
Keyword(s):  
Electron Transport ◽  
Complex I ◽  
Electron Transport Chain ◽  
Developmental Stages ◽  
Photosynthetic Electron Transport ◽  
Cytochrome F ◽  
Plastid Development ◽  
Photosynthetic Electron Transport Chain ◽  
Nadh Ubiquinone Oxidoreductase ◽  
Transport Chain

Abstract Plastids contain a NAD(P)H-plastoquinone-oxidoreductase which is homologous to the eubacterial and mitochondrial NADH-ubiquinone-oxidoreductase (complex I), but the meta­bolic function of the enzyme is still not yet understood. The enzyme consists of at least eleven subunits (NDH-A-K), which are all encoded in the plastid chromosome. In this study we have investigated the tissue-specific and light-dependent expression of the subunits NDH-H and NDH-K in maize, rice and mustard by western blot analysis. No NDH-proteins were found in root tissue, indicating that the presence of the enzyme is confined to leaf plastids. Analysis of the expression during the light-dependent development from etioplasts to chloro­plasts showed that high amounts of NDH-H and -K are present in etioplasts. The same result was found for subunits of the ATPase. In contrast, components of the photosynthetic electron transport chain (PSII-B, cytochrome f and PSI-D) accumulated only after illumination. In an second investigation, the expression of NDH-proteins along the natural chloroplast develop­ mental gradient from proplastids to chloroplasts in light-grown maize leaves was analysed. NDH-H and NDH-K as well as the ATPase were present at the youngest stages of chloro­plast development, while the massive accumulation of subunits of the photosystems and the cytochrome b6/f-complex took place in older leaf sections. We conclude from these studies that a functional NAD(P)H-plastoquinone-oxidoreductase is present in etioplasts and devel­oping plastids. We suggest that the enzyme serves the generation of a proton gradient across the prothylakoid membrane that is necessary for protein integration into the membrane at developmental stages where a functional photosynthetic electron transport chain is not yet operating.

scholarly journals The energy-linked transhydrogenase reaction in respiratory mutants of Escherichia coli K 12

1971 ◽  
Vol 125 (2) ◽  
pp. 489-493 ◽  
Author(s):  
G. B. Cox ◽  
N. A. Newton ◽  
J. D. Butlin ◽  
F. Gibson
Keyword(s):  
Escherichia Coli ◽  
Energy Source ◽  
Electron Transport ◽  
Electron Transport Chain ◽  
Adenosine Triphosphatase ◽  
E Coli ◽  
Transport Chain ◽  
Mutant Strains ◽  
K 12 ◽  
A Site

1. Energy-linked and non-energy-linked transhydrogenase activities were assayed in membrane preparations from normal Escherichia coli K 12 and from various mutant strains. 2. The energy-linked transhydrogenase, which uses ATP as energy source, was dependent for activity on the presence of a functional Mg2++Ca2+-stimulated adenosine triphosphatase. 3. Neither of the quinones formed by E. coli, namely ubiquinone-8 and menaquinone-8, was required for normal ATP-dependent energy-linked transhydrogenase activity. 4. The energy-linked transhydrogenase was inhibited by piericidin A at a site unrelated to the sites of inhibition of the electron-transport chain by piericidin A.

scholarly journals Energy coupling sites in the electron transport chain ofZymomonas mobilis

1995 ◽  
Vol 133 (1-2) ◽  
pp. 99-104 ◽  
Author(s):  
U. Kalnenieks ◽  
N. Galinina ◽  
I. Irbe ◽  
M. Toma
Keyword(s):  
Electron Transport ◽  
Electron Transport Chain ◽  
Energy Coupling ◽  
Transport Chain

scholarly journals Complete inhibition of dihydro-orotate oxidation and superoxide production by 1,1,1-trifluoro-3-thenoylacetone in rat liver mitochondria

1985 ◽  
Vol 225 (1) ◽  
pp. 189-194 ◽  
Author(s):  
K N Dileepan ◽  
J Kennedy
Keyword(s):  
Electron Transport ◽  
Dehydrogenase Activity ◽  
Rat Liver ◽  
Electron Transport Chain ◽  
Chelating Agent ◽  
Liver Mitochondria ◽  
Complete Inhibition ◽  
Rat Liver Mitochondria ◽  
Transport Chain ◽  
A Site

1,1,1-Trifluoro-3-thenoylacetone was shown to cause complete inhibition of dihydroorotate oxidation in rat liver mitochondria as measured by orotate formation and the rate of dihydro-orotate-dependent reduction of 2,6-dichlorophenol-indophenol or cytochrome c. The inhibition by trifluorothenoylacetone was dose-dependent, and a concentration of 1 mM completely inhibited dihydro-orotate dehydrogenase activity. 1,10-Phenanthroline, another iron-chelating agent, also caused total inhibition of the liver enzyme. Whereas the iron chelators inhibited 100% of dihydro-orotate dehydrogenase activity in liver mitochondria, they inhibited only a maximum of 72% in the case of the brain enzyme. The inhibition by trifluorothenoylacetone was not prevented by addition of phenazine methosulphate or ubiquinone. Dihydro-orotate dehydrogenase-mediated generation of superoxide was abolished when the enzyme was fully inhibited by trifluorothenoylacetone or when the electron-transport system was blocked by antimycin A. These results suggest that the iron component(s) of dihydro-orotate dehydrogenase is of strategic importance for catalytic activity and transfer of reducing equivalents from the primary enzyme to the electron-transport chain. Furthermore, the study indicates that production of superoxide radicals during dihydro-orotate dehydrogenase-catalysed oxidation of dihydro-orotate may be at the cytochrome b-c1 segment of the electron-transport chain (as a consequence of autooxidation of ubisemiquinone) rather than at a site on the primary enzyme.

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