scholarly journals The electron-transport system of mitochondria from the slime mould Physarum polycephalum

1973 ◽  
Vol 134 (3) ◽  
pp. 745-751 ◽  
Author(s):  
Roger Barnes ◽  
Emer M. Colleran ◽  
O. T. G. Jones
Keyword(s):  
Steady State ◽  
Electron Transport ◽  
Cytochrome C ◽  
Cytochrome B ◽  
Transport System ◽  
Physarum Polycephalum ◽  
Respiratory Activity ◽  
Slime Mould ◽  
Aerobic And Anaerobic ◽  
Α Band

A method is described for the preparation of mitochondria from the slime mould Physarum polycephalum; the mitochondria were not coupled. P. polycephalum mitochondria oxidized added NADH via a rotenone-insensitive pathway, but the oxidation of malate plus glutamate was rotenone sensitive; both of these substrates reduced much less cytochrome b than did succinate, in both aerobic and anaerobic steady states. Spectroscopy at 77°K separated three absorption maxima in the α-band region, at 560nm, 553nm and one at 547nm due to cytochrome c. The absorption at 553nm was increased in the aerobic steady state by the addition of 2-heptyl-4-hydroxyquinoline N-oxide, suggesting that it was due to a b-type cytochrome. All three absorption maxima appeared in the aerobic steady state after the addition of a range of substrates. The respiratory activity with different substrates and the response to inhibitors of respiration were similar to those previously described for fungus mitochondria (Weiss et al., 1970; Erickson & Ashworth, 1969). When grown under conditions of haem limitation the mitochondria contained a lower concentration of cytochromes than normal.

The multiple roles of the mitochondrion of the malarial parasite

Parasitology ◽  
2004 ◽  
Vol 129 (5) ◽  
pp. 511-524 ◽  
Author(s):  
J. KRUNGKRAI
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Transport System ◽  
Antimalarial Drug ◽  
Tricarboxylic Acid Cycle ◽  
Coenzyme Q ◽  
Complex Iii ◽  
Electron Transport System ◽  
Complex Ii ◽  
Dehydrogenase Complex

Mitochondria of the malaria parasitePlasmodium falciparumare morphologically different between the asexual and sexual blood stages (gametocytes). In this paper recent findings of mitochondrial heterogeneity are reviewed based on their ultrastructural characteristics, metabolic activities and the differential expression of their genes in these 2 blood stages of the parasite. The existence of NADH dehydrogenase (complex I), succinate dehydrogenase (complex II), cytochrome c reductase (complex III) and cytochrome c oxidase (complex IV) suggests that the biochemically active electron transport system operates in this parasite. There is also an alternative electron transport branch pathway, including an anaerobic function of complex II. One of the functional roles of the mitochondrion in the parasite is the coordination of pyrimidine biosynthesis, the electron transport system and oxygen utilization via dihydroorotate dehydrogenase and coenzyme Q. Complete sets of genes encoding enzymes of the tricarboxylic acid cycle and the ATP synthase complex are predicted fromP. falciparumgenomics information. Other metabolic roles of this organelle include membrane potential maintenance, haem and coenzyme Q biosynthesis, and oxidative phosphorylation. Furthermore, the mitochondrion may be a chemotherapeutic target for antimalarial drug development. The antimalarial drug atovaquone targets the mitochondrion.

scholarly journals The microbial metabolism of C1 compounds. The electron-transport chain of Pseudomonas AM1

1975 ◽  
Vol 152 (2) ◽  
pp. 349-356 ◽  
Author(s):  
David Widdowson ◽  
Christopher Anthony
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Redox Potential ◽  
Molecular Oxygen ◽  
Cytochrome B ◽  
Electron Transport Chain ◽  
Difference Spectrum ◽  
Reduced Form ◽  
Transport Chain ◽  
Oxidation By Molecular Oxygen

Pseudomonas AM1, Hyphomicrobium X and Pseudomonas MS all contain cytochrome a/a3 and a b-type cytochrome able to react with CO. Pseudomonas AM1 and Hyphomicrobium X also have a CO-binding cytochrome c. The purified cytochrome c (redox potential 0.26V) of Pseudomonas AM1 was not susceptible to oxidation by molecular oxygen. CO reacted slowly with the reduced form giving a CO difference spectrum with a peak at 412nm and troughs at 420nm and 550nm. Similar results were obtained with the cytochrome c of Hyphomicrobium (aerobically grown or anaerobically grown with nitrate) and with that of Pseudomonas extorquens. The results given in the present paper are incompatible with an oxygenase or oxidase function for the soluble cytochrome c of methylotrophs. Studies with whole cells of Pseudomonas AM1 and a cytochrome c-deficient mutant have demonstrated that cytochrome b (redox potential 0.009V) is the first cytochrome in the electron-transport chain for oxidation of all substrates except methanol (and ethanol) whose oxidation does not involve this cytochrome. All substrates are usually oxidized by way of cytochrome c and cytochrome oxidase (cytochrome a/a3), but there is an alternative route for the reduction of cytochrome a/a3 in the mutant lacking cytochrome c. Results of experiments on cyanide inhibition of respiration and cytochrome oxidation support the suggestion that the susceptibility of cytochrome b to oxidation by molecular oxygen (reflected in its ability to react with CO) is probably irrelevant to the normal physiology of Pseudomonas AM1.

Effect of prolonged cold exposure on components of the electron transport system

1960 ◽  
Vol 198 (4) ◽  
pp. 740-744 ◽  
Author(s):  
John P. Hannon
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Cytochrome Oxidase ◽  
Transport System ◽  
Cold Exposure ◽  
Liver Tissue ◽  
Succinic Dehydrogenase ◽  
Electron Transport System ◽  
Malic Dehydrogenase ◽  
Cytochrome C Reductase

The effect of 3–4 weeks exposure to 5° ± 1°C on the activity of enzymes associated with the electron transport system of rat liver and gastrocnemius muscle was investigated. The enzymes included lactic, succinic and malic dehydrogenase, DPNH-cytochrome c reductase and cytochrome oxidase. Cold exposure led to increased activities on the part of succinic and malic dehydrogenase and cytochrome oxidase. Muscle tissue exhibited a greater response in these components than liver tissue. Lactic dehydrogenase and DPNH-cytochrome c reductase activities were unaffected by cold exposure in either liver or muscle. Thyroxine, 2,4-dinitrophenol, phosphate and hexokinase-glucose stimulated the activity of succinic dehydrogenase activities of liver tissue, with hexokinase-glucose producing the greatest effect. The degree of stimulation by these agents was the same, however, for tissue from cold exposed animals as it was for controls. It was concluded that the increased tissue oxygen consumption in the cold-acclimatized rat was attributable to at least three mechanisms: a) an increased enzyme concentrations; b) a stimulation of latent enzyme activity; and c) an uncoupling of oxidative phosphorylation.

Effect of magnesium ions on the activity of the cytosolic NADH/cytochrome c electron transport system

FEBS Journal ◽  
2008 ◽  
Vol 275 (24) ◽  
pp. 6168-6179 ◽  
Author(s):  
Gianluigi La Piana ◽  
Vincenza Gorgoglione ◽  
Daniela Laraspata ◽  
Domenico Marzulli ◽  
Nicola E. Lofrumento
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Transport System ◽  
Electron Transport System ◽  
Magnesium Ions ◽  
Nadh Cytochrome
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