EPR signals of NADH: Q oxidoreductase shape and intensity

Isolation and characterization of three subcomplexes of the mitochondrial NADH: ubiquinone oxidoreductase (complex I). Finel, M.; Majander, A.S.; Tyynela, J.; de Jong, A.M.P.; Albracht, S.P.J.; Wilkstrom, M. General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Download date: 10 May 2018Eur. J. Biochem. 226, 237-242 (1994) Enzymically active subcomplexes were purified from bovine mitochondrial NADH :ubiquinone oxidoreductase (complex I) by sucrose-gradient centrifugation in the presence of detergents. These subcomplexes, named 12, IS, and US, catalyse ferricyanide and ubiquinone-1 (Q-1) reduction by NADH at similar rates to complex I, but do not catalyse the reduction of decylubiquinone. In addition, the Q-1 reductase activity of all the subcomplexes is insensitive to rotenone. Chemical and EPR analyses of the subcomplexes show that FMN and all the Fe-S clusters of complex I are present, but that the line shape of cluster 2 is modified. The smallest subcomplex, US, contains only approximately 13 subunits, as compared to approximately 22 in the previously described sub-

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“…redox mediators (Albracht et al, 1977). However, no Fe-S cluster was detected upon reduction of subcomplex 1).…”

Section: Fig 2 Epr Spectra Of Subcomplexes I1iis and Is Compared Tmentioning

confidence: 94%

Isolation and Characterisation of Subcomplexes of the Mitochondrial NADH: Ubiquinone Oxidoreductase (Complex I)

Finel¹,

Majander²,

Tyynelä³

et al. 1994

Eur J Biochem

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“…The e.p.r. properties of these enzymes have been documented in great detail in the literature [23][24][25][26][27][28][29][30][31][32][33][34][35]. With this information it is straightforward to identify in Fig.…”

Section: Sample Preparationmentioning

confidence: 99%

Reappraisal of the e.p.r. signals in (post)-ischaemic cardiac tissue

Kraaij

Koster

Hagen

1989

Biochemical Journal

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The present study was designed to measure directly, using e.p.r. spectroscopy, oxygen-derived free radicals in (post)-ischaemic or (post)-anoxic rat hearts. Rat hearts were rapidly freeze-clamped at 77 K under normoxic, anoxic, ischaemic or reperfusion conditions. The samples were measured at three different temperatures (13, 77 and 115 K) and at several microwave power levels, and were compared with isolated rat heart mitochondria. Samples were prepared both by grinding and as tissue cuts. The two preparation techniques gave identical e.p.r. results, which excludes the occurrence of grinding artifacts. No free radical signals linked to reperfusion injury were detected. Several electron transfer centres known in the mitochondrial respiratory chain were measured. The signals previously assigned to post-ischaemic reperfusion injury were found to originate from electron transfer centres of the respiratory chain, predominantly the iron-sulphur cluster S-1 in succinate dehydrogenase. The differences in signal intensity between normoxic, ischaemic and reperfused hearts were found to result from the different redox stages of these centres under the various conditions tested. These findings do not necessarily imply that oxygenderived free radicals are not formed in cardiac tissue during (post)-ischaemic reperfusion. The constitutive background of paramagnetism from the respiratory chain, however, seriously hampers the direct detection of comparatively low concentrations of free radicals in cardiac tissue. It is therefore expedient to focus future experiments in this field on the use of spin-trapping agents.

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“…The signals of the other clusters are not affected. This instability is introduced in Hatefi's isolation procedure (Hatefi et al 1962) at the step where Complex I-III is prepared from Complex I-II-III (Albracht et al 1977). The presence of dithionite, which effectively consumes all O 2 , prevents these NADH-induced changes (Albracht et al 1977).…”

Section: Reactions Of O 2 With Purified Complex I and Nadh Dehydrogenmentioning

confidence: 99%

“…This instability is introduced in Hatefi's isolation procedure (Hatefi et al 1962) at the step where Complex I-III is prepared from Complex I-II-III (Albracht et al 1977). The presence of dithionite, which effectively consumes all O 2 , prevents these NADH-induced changes (Albracht et al 1977). A g=1.97 line, a marker for the NADH-induced instability, is also present in Hirst's NADH dehydrogenase upon reduction with NADH (Sharpley et al 2006).…”

Section: Reactions Of O 2 With Purified Complex I and Nadh Dehydrogenmentioning

confidence: 99%

Mammalian NADH:ubiquinone oxidoreductase (Complex I) and nicotinamide nucleotide transhydrogenase (Nnt) together regulate the mitochondrial production of H2O2—Implications for their role in disease, especially cancer

Albracht

Meijer

Rydström

2011

J Bioenerg Biomembr

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Mammalian NADH:ubiquinone oxidoreductase (Complex I) in the mitochondrial inner membrane catalyzes the oxidation of NADH in the matrix. Excess NADH reduces nine of the ten prosthetic groups of the enzyme in bovine-heart submitochondrial particles with a rate of at least 3,300 s −1 . This results in an overall NADH→O 2 rate of ca. 150 s −1 . It has long been known that the bovine enzyme also has a specific reaction site for NADPH. At neutral pH excess NADPH reduces only three to four of the prosthetic groups in Complex I with a rate of 40 s −1 at 22°C. The reducing equivalents remain essentially locked in the enzyme because the overall NADPH→O 2 rate (1.4 s −1 ) is negligible. The physiological significance of the reaction with NADPH is still unclear. A number of recent developments has revived our thinking about this enigma. We hypothesize that Complex I and the Δp-driven nicotinamide nucleotide transhydrogenase (Nnt) co-operate in an energy-dependent attenuation of the hydrogen-peroxide generation by Complex I. This co-operation is thought to be mediated by the NADPH/NADP + ratio in the vicinity of the NADPH site of Complex I. It is proposed that the specific H 2 O 2 production by Complex I, and the attenuation of it, is of importance for apoptosis, autophagy and the survival mechanism of a number of cancers. Verification of this hypothesis may contribute to a better understanding of the regulation of these processes.

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EPR signals of NADH: Q oxidoreductase shape and intensity

Cited by 83 publications

References 19 publications

Isolation and Characterisation of Subcomplexes of the Mitochondrial NADH: Ubiquinone Oxidoreductase (Complex I)

Isolation and Characterisation of Subcomplexes of the Mitochondrial NADH: Ubiquinone Oxidoreductase (Complex I)

Reappraisal of the e.p.r. signals in (post)-ischaemic cardiac tissue

Mammalian NADH:ubiquinone oxidoreductase (Complex I) and nicotinamide nucleotide transhydrogenase (Nnt) together regulate the mitochondrial production of H2O2—Implications for their role in disease, especially cancer

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