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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of bioenergetics and biomembranes 16 (1984), S. 153-166 
    ISSN: 1573-6881
    Keywords: NADH oxidase ; NADH dehydrogenase ; NADH-ubiquinone reductase ; ubiquinone homologs ; rotenone ; submitochondrial particles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The combined effects of rotenone and ubiquinone-3 on the kinetics of NADH dehydrogenase and NADH oxidase have been investigated. The two inhibitors do not show additivity; on the other hand, ubiquinone-3, when preincubated with the enzyme, partially removes rotenone sensitivity. The inhibition of NADH oxidase by ubiquinone-3 is the result of at least two combined effects: the competition of the less active ubiquinone-3 with endogenous ubiquinone-10 in the acceptor site of the dehydrogenase, and a nonspecific action on the structure of complex I. The latter effect is perhaps mediated by a physical change of the phospholipid bilayer similar to that observed with agents such as butanol, perturbing lipid-protein interactions in the membrane.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-6881
    Keywords: Ubiquinone-depleted mitochondria ; succinate-ferricyanide reductase ; bc 1 complex ; cytochromeb
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Depletion of endogenous ubiquinone by pentane extraction of mitochondrial membranes lowered succinate-ferricyanide reductase activity, whereas quinone reincorporation restored the enzymatic activity as well as antimycin sensitivity. The oxidant-induced cytochromeb extrareduction, normally found upon ferricyanide pulse in intact mitochondria in the presence of antimycin, was lost in ubiquinone-depleted membranes, even if cytochromec was added. Readdition of ubiquinone-2 restored the oxidant-induced extrareduction with an apparent half saturation at 1 mol/molbc 1 complex saturating at about 5 mol/mol. These findings demonstrate a requirement for the ubiquinone pool of the cytochromeb extrareduction. Since the initial rates of cytochromeb reoxidation upon ferricyanide addition, in the presence of antimycin, did not saturate by any ferricyanide concentration in ubiquinone-depleted mitochondria, a direct chemical reaction between ferricyanide and reduced cytochromeb was postulated. The fact that such direct reaction is much faster in ubiquinone-depleted mitochondria may explain the lower antimycin sensitivity of the succinate ferricyanide reductase activity after removal of endogenous ubiquinone.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 1 (1973), S. 194-207 
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Proteolytic enzymes, pronase and trypsin, digest protein in ETP and in SU-particles (devoid of the soluble ATPase) at similar rates and to the same extents for intact and lipid-depleted membranes, showing that lipids do not constitute a barrier to the action of the proteases. The rates and extents of hydrolysis are slightly depressed when membranes are reconstituted from lipid-depleted particles and phospholipids. The hydrolysis rates for the various particles are not greatly enhanced by detergent solubilization nor by other denaturing treatments, indicating that the rates measured in absence of treatments are maximal under the conditions used. The circular dichroism spectra of pronase treated ETP are noticeably altered showing modification of the original conformation. Moreover, enzymic activities of mitochondria and submitochondrial particles are progressively affected by proteases according to their localization at, or near to, a given surface of the membrane. The matrix enzyme, malate dehydrogenase, is not apparently released from mitochondria during the initial incubation period. The results are tentatively discussed in terms of organization of lipids and proteins in the mitochondrial membrane.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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