Respiratory supercomplexes enhance electron transport by decreasing cytochrome
            c
            diffusion distance

A comparative study was undertaken to examine the succinate and terminal oxidase activities of the electron-transport systems of Azotobacter vinelandii and mammalian mitochondria. For succinate oxidation, both systems exhibited similar relative specificities for the electron acceptors phenazine methosulfate, O2, methylene blue, K3Fe(CN)6, nitrotetrazolium blue, 2,6-dichlorophenolindophenol (DCIP), and cytochrome c. They differed in that DCIP and cytochrome c were less active in the Azotobacter electron-transport system (R3 fraction) than in the bovine mitochondrial system. Comparative studies with known inhibitors of mammalian mitochondrial electron-transport demonstrated that the succinoxidase activity of the Azotobacter R3 fraction was, at least, 2000 times less sensitive to antimycin A, 700 times less sensitive to thenoyl-trifluoroacetone, and 30 times less sensitive to 2-n-heptyl-4-hydroxy-quinoline-N-oxide. Both systems were equally sensitive to KCN, p-chloromercuribenzoic acid, and chlorpromazine.The ability of the two systems to use tetramethyl-p-phenylenediamine (TMPD) and its derivatives as electron donors, for terminal oxidation, was also similar. Studies on steady state reduction revealed that in the Azotobacter R3 fraction, the cytochromes (a2, a1, b1, c4 + c5) and flavoprotein components were reduced substantially by succinate as well as by TMPD in the presence of ascorbate. Ultrastructure analyses of the Azotobacter R3 electron-transport fraction revealed the vesicular membranous components identified as oxidosomes according to the terminology used by DeLey and contained spherical headpiece units of 80 Å in diameter which appeared to be morphologically identical with the tripartite units or the elementary particles described by Green and associates, viz., Kopaczyk et al., and by Fernandez-Moran et al.

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Electron Transport and Coupled Energy Generation in Pseudomonas saccharophila

Canadian Journal of Biochemistry ◽

10.1139/o71-169 ◽

1971 ◽

Vol 49 (11) ◽

pp. 1175-1182 ◽

Cited By ~ 5

Author(s):

M. Ishaque ◽

A. Donawa ◽

M. I. H. Aleem

Keyword(s):

Oxygen Consumption ◽

Electron Transport ◽

Cytochrome C ◽

Atp Synthesis ◽

Succinate Oxidation ◽

Atp Formation ◽

Low Concentrations ◽

Oxidase Enzyme ◽

Succinate Oxidase ◽

Pseudomonas Saccharophila

The respiratory chain system of heterotrophically grown Pseudomonas saccharophila contained cytochromes of the b, c, a, and o types and also the NADH and succinate oxidase enzyme systems. Cell-free extracts catalyzed phosphorylation coupled to the oxidation of NADH, succinate, and ascorbate (plus cytochrome c). The P/O ratios were in the range of 1.00 for generated NADH, 0.29 for added NADH, 0.50 for succinate, and 0.25 for ascorbate (plus cytochrome c).The oxidative phosphorylation was uncoupled by 2,4-dinitrophenol, 2,6-dibromophenol, pentachlorophenol, m-chlorocarbonyl cyanide phenylhydrazone, and dicumarol without any inhibition of oxygen consumption. Phosphorylation coupled to NADH oxidation was completely inhibited by the flavoprotein inhibitors such as rotenone, amytal, and atabrine; these inhibitors had no effect, however, on the ATP synthesis associated with succinate oxidation. Antimycin A or 2-n-nonyl-4-hydroxyquinoline-N-oxide as well as cyanide or azide at low concentrations completely inhibited the phosphate esterification coupled to the oxidation of NADH or succinate, but had little or no effect on the oxygen consumption. Relatively higher concentrations of oligomycin were required for a complete inhibition of the electron-transport-linked ATP formation.

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Effects of L-Malate on Mitochondrial Oxidoreductases in Liver of Aged Rats

Physiological Research ◽

10.33549/physiolres.931986 ◽

2011 ◽

pp. 329-336 ◽

Cited By ~ 5

Author(s):

J.-L. WU ◽

Q.-P. WU ◽

Y.-P. PENG ◽

J.-M. ZHANG

Keyword(s):

Electron Transport ◽

Cytochrome C ◽

Cytochrome C Oxidase ◽

Electron Transport Chain ◽

Nadh Dehydrogenase ◽

Tricarboxylic Acid Cycle ◽

Radical Scavenger ◽

Aged Rats ◽

Transport Chain ◽

Nadh Cytochrome

Accumulation of oxidative damage has been implicated to be a major causative factor in the decline in physiological functions that occur during the aging process. The mitochondrial respiratory chain is a powerful source of reactive oxygen species (ROS), considered as the pathogenic agent of many diseases and aging. L-malate, a tricarboxylic acid cycle intermediate, plays an important role in transporting NADH from cytosol to mitochondria for energy production. Previous studies in our laboratory reported L-malate as a free radical scavenger in aged rats. In the present study we focused on the effect of L-malate on the activities of electron transport chain in young and aged rats. We found that mitochondrial membrane potential (MMP) and the activities of succinate dehydrogenase, NADH-cytochrome c oxidoreductase and cytochrome c oxidase in liver of aged rats were significantly decreased when compared to young control rats. Supplementation of L-malate to aged rats for 30 days slightly increased MMP and improved the activities of NADH-dehydrogenase, NADH-cytochrome c oxidoreductase and cytochrome c oxidase in liver of aged rats when compared with aged control rats. In young rats, L-malate administration increased only the activity of NADH-dehydrogenase. Our result suggested that L-malate could improve the activities of electron transport chain enzymes in aged rats

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[5] Use of artificial electron acceptors for abbreviated phosphorylating electron transport: Flavin-cytochrome c

Methods in Enzymology - Oxidation and Phosphorylation ◽

10.1016/0076-6879(67)10008-6 ◽

1967 ◽

pp. 33-37 ◽

Cited By ~ 46

Author(s):

Chuan-pu Lee ◽

Gian Luigi Sottocasa ◽

Lars Ernster

Keyword(s):

Electron Transport ◽

Cytochrome C ◽

Electron Acceptors

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The Role of Mitochondrial Cytochrome c in Electron Transport

Cytochromes c - Springer Series in Molecular Biology ◽

10.1007/978-3-642-72698-9_2 ◽

1987 ◽

pp. 29-111 ◽

Cited By ~ 4

Author(s):

Graham W. Pettigrew ◽

Geoffrey R. Moore

Keyword(s):

Electron Transport ◽

Cytochrome C ◽

Mitochondrial Cytochrome ◽

Mitochondrial Cytochrome C

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Acute inhibition of respiratory capacity of muscle reduces peak oxygen consumption

AJP Cell Physiology ◽

10.1152/ajpcell.1990.259.6.c889 ◽

1990 ◽

Vol 259 (6) ◽

pp. C889-C896 ◽

Cited By ~ 61

Author(s):

R. M. McAllister ◽

R. L. Terjung

Keyword(s):

Oxygen Consumption ◽

Electron Transport ◽

Cytochrome C ◽

Peak Oxygen Consumption ◽

Dependent Manner ◽

Cytochrome C Reductase ◽

Energy Demands ◽

Hindlimb Muscle ◽

Nadh Cytochrome

Electron transport capacity of skeletal muscle was inhibited in situ in an acute dose-dependent manner with myxothiazol, a tight-binding inhibitor of ubiquinone-cytochrome c reductase, complex III of the respiratory chain. Peak oxygen consumption of rat hindlimb muscle was determined via consecutive 10-min isometric contraction (100 ms at 100 Hz) periods of increasing energy demands (4, 8, 15, 30, 45, and 60 tetani/min), using an isolated hindlimb preparation perfused with a high oxygen delivery (approximately 6-8 mumol.min-1.g-1). Peak oxygen consumption decreased from 4.61 +/- 0.19 mumol.min-1.g-1 (control) in a dose-dependent manner to 0.73 +/- 0.07 mumol.min-1.g-1 at 0.50 microM myxothiazol in blood. Oxygen extraction decreased from 65 to 12% of delivered oxygen. Furthermore, the reduction in peak respiratory rate became evident at lower energy demands of the contraction sequence. Myxothiazol inhibition of respiration was not dependent on the presence of muscle contractions but was evident when mitochondria were uncoupled with carbonyl cyanide m-chlorophenylhydrazone. A 50% effective dosage (ED50) of 0.21 microM myxothiazol for inhibition of peak oxygen consumption closely resembled the inhibition of NADH-cytochrome c reductase activity (ED50 of 0.27 microM) determined from homogenates of the same muscles. This suggests that the peak oxygen consumption of skeletal muscle is tightly coupled to the capacity for electron transport evaluated by flux through NADH-cytochrome c reductase. If the enzyme activity measured in vitro correctly represents available enzymatic capacity within contracting muscle, approximately 75% of electron transport capacity for handling reducing equivalents generated from NADH is utilized during peak oxygen consumption of rat hindlimb muscle contracting in situ.

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