The Iron−Sulfur Clusters 2 and Ubisemiquinone Radicals of NADH:Ubiquinone Oxidoreductase Are Involved in Energy Coupling in Submitochondrial Particles

Belzen, R. van; Kotlyar, Alexander; Moon, Namdoo; Dunham, William; Albracht, S.P.J.

doi:10.1021/bi9612982

Cited by 72 publications

(35 citation statements)

References 37 publications

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“…The electrochemical potential around -150 mV across the inner mitochondrial membrane therefore drives the three fundamental functions of mitochondria, namely ATP generation, Ca 2+ uptake/storage, and generation/detoxification of ROS (27,(35)(36)(37).…”

Section: Mitochondrial Functionmentioning

confidence: 99%

Sevoflurane depolarizes pre‐synaptic mitochondria in the central nervous system

Moe¹,

Bains²,

Vinje³

et al. 2004

Acta Anaesthesiol Scand

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Background: Volatile anaesthetics protect the heart from ischaemic injury by activating mitochondrial signalling pathways. The aim of this study was to test whether sevoflurane, which is increasingly used in neuroanaesthesia, affects mitochondrial function in the central nervous system by altering the mitochondrial membrane potential (ΔΨm).Methods: In order to correlate free cytosolic Ca2+ ([Ca2+]i) and ΔΨm, rat neural presynaptic terminals (synaptosomes) were loaded with the fluorescent probes fura‐2 and JC‐1. During sevoflurane exposure, 4‐aminopyridine (4‐AP) 500 µM to induce pre‐synaptic membrane depolarization or carbonylcyanide‐p‐(trifluoromethoxy)‐phenylhydrazone (FCCP) 1 µM to induce maximum mitochondrial depolarization was added. In order to block mitochondrial ATP‐regulated K+‐channels (mitoKATP), the antagonist 5‐hydroxydecanoate (5‐HD) 500 µM was added.Results: In Ca2+‐containing medium, both sevoflurane 1 and 2 MAC gradually decreased the normalized JC‐1 ratio from 0.96 ± 0.01 in control to 0.92 ± 0.01 and 0.89 ± 0.01, representing a depolarization of ΔΨm (n = 9, P < 0.05). Sevoflurane 2 MAC increased [Ca2+]i. In Ca2+‐depleted medium, sevoflurane 1 and 2 MAC depolarized ΔΨm, while [Ca2+]i remained unaltered. Sevoflurane 2 MAC attenuated the 4‐AP‐induced depolarization of ΔΨm. When mitoKATP was blocked, the sevoflurane‐induced depolarization of ΔΨm was attenuated, but not blocked. The depolarizing effect of sevoflurane on ΔΨm compared with FCCP was calculated to 13.2 ± 1.3% in Ca2+‐containing and 15.1 ± 1.2% in Ca2+‐depleted medium (n = 7).Conclusions: Sevoflurane depolarizes ΔΨm in rat synaptosomes, and the effect is not dependent on Ca2+‐influx to the cytosol. Opening of mitoKATP is partly responsible for the depolarizing effect of sevoflurane.

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Section: Mitochondrial Functionmentioning

confidence: 99%

Sevoflurane depolarizes pre‐synaptic mitochondria in the central nervous system

Moe¹,

Bains²,

Vinje³

et al. 2004

Acta Anaesthesiol Scand

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“…The number of reported ubiquinone binding sites varies depending on the author but the consensus right now is 3 binding sites (69). Two semiquinones are readily detectable by EPR (135)(136)(137) and there may be as many as three operational Q cycles (68,69,135,136,138). Several mechanisms have been proposed to explain the 4H § electron stoichiometry.…”

Section: Production At Complex Imentioning

confidence: 99%

“…The structural information, that is, the general shape of the complex and position of the iron sulfur clusters, is not arbitrary but based on experimental evidence. The distance relationships between the semiquinones and the iron sulfur proteins, as well as the general placement of the subunits, are based on EPR (68,(135)(136)(137). Both models predict the existence of Qo-type sites, defined earlier as quinol oxidation sites facing the intermembrane space (139).…”

Section: Production At Complex Imentioning

confidence: 99%

The nature and mechanism of superoxide production by the electron transport chain: Its relevance to aging

Muller

2000

AGE

120

123

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Most biogerontologists agree that oxygen (and nitrogen) free radicals play a major role in the process of aging. The evidence strongly suggests that the electron transport chain, located in the inner mitochondrial membrane, is the major source of reactive oxygen species in animal cells. It has been reported that there exists an inverse correlation between the rate of superoxide/hydrogen peroxide production by mitochondria and the maximum longevity of mammalian species. However, no correlation or most frequently an inverse correlation exists between the amount of antioxidant enzymes and maximum longevity. Although overexpression of the antioxidant enzymes SOD1 and CAT (as well as SOD1 alone) have been successful at extending maximum lifespan in Drosophila, this has not been the case in mice. Several labs have overexpressed SOD1 and failed to see a positive effect on longevity. An explanation for this failure is that there is some level of superoxide damage that is not preventable by SOD, such as that initiated by the hydroperoxyl radical inside the lipid bilayer, and that accumulation of this damage is responsible for aging. I therefore suggest an alternative approach to testing the free radical theory of aging in mammals. Instead of trying to increase the amount of antioxidant enzymes, I suggest using molecular biology/ transgenics to decrease the rate of superoxide production, which in the context of the free radical theory of aging would be expected to increase longevity. This paper aims to summarize what is known about the nature and mechanisms of superoxide production and what genes are involved in controlling the rate of superoxide production.

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“…A series of studies of the inhibition mechanism of MPP ϩ analogues by Singer and colleagues (6 -10) have suggested that MPP ϩ analogues are bound at two sites in the enzyme, one accessible to relatively hydrophilic inhibitors (termed the "hydrophilic site") and one shielded by a hydrophobic barrier on the enzyme (the "hydrophobic site"), and that occupation of both sites is required for complete inhibition. This concept may be helpful in elucidating the terminal electron transfer step in complex I and seems to be consistent with the existence of two EPR-detectable species of complex I-associated ubisemiquinones (11,12). Some experimental results with ordinary complex I inhibitors (13-16) can be explained by assuming the existence of more than one inhibitor (or ubiquinone) binding site.…”

mentioning

confidence: 62%

Specificity of Pyridinium Inhibitors of the Ubiquinone Reduction Sites in Mitochondrial Complex I

Miyoshi

Iwata

Sakamoto

et al. 1998

Journal of Biological Chemistry

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I) 1 is a large enzyme that catalyzes the oxidation of NADH by ubiquinone coupled to proton translocation across the inner membrane (1, 2). There are a variety of inhibitors of mitochondrial complex I and with the exception of a few inhibitors which inhibit electron input into the enzyme (3, 4), all inhibitors act at or close to the ubiquinone reduction site (5). Among the inhibitors, positively charged neurotoxic N-methyl-4-phenylpyridinium (MPP ϩ ) and its alkyl analogues exhibit unique inhibitory behavior with bovine heart mitochondrial complex I (6). A series of studies of the inhibition mechanism of MPP ϩ analogues by Singer and colleagues (6 -10) have suggested that MPP ϩ analogues are bound at two sites in the enzyme, one accessible to relatively hydrophilic inhibitors (termed the "hydrophilic site") and one shielded by a hydrophobic barrier on the enzyme (the "hydrophobic site"), and that occupation of both sites is required for complete inhibition. This concept may be helpful in elucidating the terminal electron transfer step in complex I and seems to be consistent with the existence of two EPR-detectable species of complex I-associated ubisemiquinones (11,12). Some experimental results with ordinary complex I inhibitors (13-16) can be explained by assuming the existence of more than one inhibitor (or ubiquinone) binding site.In the previous study (17), we synthesized a series of MPP ϩ analogues which are much more potent than the original MPP ϩ and demonstrated that the presence of hydrophobic counteranion tetraphenylboron (TPB Ϫ ) potentiates the inhibition by MPP ϩ analogues differently depending upon the molar ratio of TPB Ϫ to the inhibitors. In the presence of a catalytic amount of TPB Ϫ , the inhibitory potency of MPP ϩ analogues was markedly enhanced, and the extent of inhibition was almost complete. The presence of an excess amount of TPB Ϫ partially reactivated the enzyme activity, and the inhibition was partly saturated (ϳ50%). This complicated inhibitory behavior could be explained by the dual binding sites model mentioned above (6), which supposes quite different hydrophobic natures of the two sites and/or their environments.If there are indeed two distinct binding sites of MPP ϩ analogues in bovine complex I, there should be specific inhibitors which act selectively at one of the two proposed binding sites since it is unlikely that the structural properties of the two sites are completely identical. We have synthesized such a selective inhibitor, MP-6 (N-methyl-4-[2-(p-tert-butylbenzyl)-propyl]pyridinium, Fig. 1) (17). In the absence of TPB Ϫ , this inhibitor showed approximately 50% inhibition at 5 M in NADH-Q 1 oxidoreductase assay, but the inhibition reached a plateau at this level over a wide range of concentrations. Weak inhibition was again observed above ϳ80 M, and maximum inhibition (Ͼ90%) was obtained only when the concentration of the inhibitor was increased to ϳ250 M. Such a marked biphasic nature of the does-response curve has not been reported previously for usual complex I i...

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The Iron−Sulfur Clusters 2 and Ubisemiquinone Radicals of NADH:Ubiquinone Oxidoreductase Are Involved in Energy Coupling in Submitochondrial Particles

Cited by 72 publications

References 37 publications

Sevoflurane depolarizes pre‐synaptic mitochondria in the central nervous system

Sevoflurane depolarizes pre‐synaptic mitochondria in the central nervous system

The nature and mechanism of superoxide production by the electron transport chain: Its relevance to aging

Specificity of Pyridinium Inhibitors of the Ubiquinone Reduction Sites in Mitochondrial Complex I

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