The Mitochondrial Membrane Potential

Tedeschi, Henry

doi:10.1111/j.1469-185x.1980.tb00692.x

Cited by 51 publications

(24 citation statements)

References 161 publications

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“…In this detailed review they could draw attention only to work using spin-labelled phosphonium salts [37] and to resonance Raman spectroscopic evidence obtained with the membrane-permeable quinaldine red cation [38] which indicated that the binding of such salts to energised membranes might cause gross overestimation of the bulk-phase A$. The criticisms of this method offered by Tedeschi [39] in the case of osmotically-active mitochondria would seem not to be applicable to intact bacterial cells. Numerous studies, e. g. [40], have shown that phosphonium ions can bind significantly to de-energised bacterial mem-branes, and it was for this reason that we were careful to base our calculations of values solely on the energy-dependent uptake of BuPh3P'.…”

Section: Does the Distribution Of Phosphonium Ions Adequately Reflectmentioning

confidence: 99%

On the Mode of Action of the Bacteriocin Butyricin 7423. Effects on Membrane Potential and Potassium-Ion Accumulation in Clostridium pasteurianum

et al. 1982

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1. The apparent transmembrane bulk-phase electrical potential ( A $ ) of Clostridium pasteurianum was determined from the distribution ratio of the membrane-permeable cation butyltriphenylphosphonium (BuPh3P+). In glycolysing cells the highest value of d $, calculated on the assumption that there was no energy-dependent binding of BuPh3P+ to the organisms, was recorded in media containing only 2-3 mM K + ions and, even so, was only 100-110mV.2. Efrapeptin, a BF,-directed inhibitor of the membrane H +-ATPase of C1. pustcuriunum, abolished the membrane potential (A$) and caused complete efflux of actively-transported K + ions. Thus protonmotive hydrolysis of ATP generated by substrate level phosphorylation is the sole means of membrane energisation in this anaerobe. 4. Whilst the addition of valinomycin to cells of C1. pasteurianum suspended in media of low K + concentration generated a diffusion potential to which BuPh3P+ would respond, addition of butyricin 7423 in place of valinomycin caused no such effect. Also, unlike valinomycin, butyricin 7423 did not increase the rate of K + efflux from nonglycolysing cells of Cl. pasteuvianum. Valinomycin stimulated, but butyricin 7423 inhibited, the uptake of 86Rb+ ions by glycolysing cells of C1. pasteurianum. 5.A mutant strain of Cl. pasteurianum (viz. strain DC3) which possessed a H+-ATPase with diminished sensitivity both to NJV"'dicyclohexy1carbodiimide and to butyricin 7423, exhibited a negligible decrease in A $ and in K + accumulation ratio in response to concentrations of butyricin 7423 that were bactericidal to the wild-type, parent organism. Even so, the bactericidal action of butyricin 7423 on C1. pasteurianum is not adequately explained by its ability in vitro to inhibit the membrane H+-ATPase of this organism.6. Bactericidal concentrations of butyricin 7423 neither provoked efflux of Na' ions from Cl. pasteurianum nor exhibited any protonophorous activity. However, at artificially high concentration, butyricin 7423 catalysed the passage of Na' ions as well as of K + ions through multilayer lipid membranes.7. As a non-protonophorous uncoupler, butyricin 7423 appears to act in a similar manner to that of the membrane-active colicins. Yet no evidence was obtained that butyricin 7423 at its minimum lethal concentration might form a gated ion channel in the cytoplasmic membrane of the target cell, or act as a classic ionophore.

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Section: Does the Distribution Of Phosphonium Ions Adequately Reflectmentioning

confidence: 99%

On the Mode of Action of the Bacteriocin Butyricin 7423. Effects on Membrane Potential and Potassium-Ion Accumulation in Clostridium pasteurianum

et al. 1982

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“…Electrons are transferred from reduced nucleotides to various intermediates of the electron transport chain during which protons are pumped across the inner membrane from the matrix into the inter membrane space. This proton transport creates a transmembrane potential (ΔΨm) (Tedeschi, 1980) which provides the motive force required for ATP synthesis, as well as for facilitating the selective entry of ions such as Ca 2+ (Siliprandi et al, 1983).…”

Section: Introductionmentioning

confidence: 99%

The mitochondrial permeability transition in neurologic disease

Norenberg

Rao

2007

Neurochemistry International

146

107

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Mitochondria, being the principal source of cellular energy, are vital for cell life. Yet, ironically, they are also major mediators of cell death, either by necrosis or apoptosis. One means by which these adverse effects occur is through the mitochondrial permeability transition (mPT) whereby the inner mitochondrial membrane suddenly becomes excessively permeable to ions and other solutes, resulting in a collapse of the inner membrane potential, ultimately leading to energy failure and cell necrosis. The mPT may also bring about the release of various factors known to cause apoptotic cell death. The principal factors leading to the mPT are elevated levels of intracellular Ca 2+ and oxidative stress. Characteristically, the mPT is inhibited by cyclosporin A. This article will briefly discuss the concept of the mPT, its molecular composition, its inducers and regulators, agents that influence its activity and describe the consequences of its induction. Lastly, we will review its potential contribution to acute neurological disorders, including ischemia, trauma, and toxic-metabolic conditions, as well as its role in chronic neurodegenerative conditions such as Alzheimer's disease, Parkinson's disease, Huntington's disease and amyotrophic lateral sclerosis.

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“…Other reports (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) have described proton movements in restricted domains or in isolated open membrane sheets not capable of sustaining a transmembrane pH gradient (which nevertheless can be energized, ostensibly by generation of an electrochemical H+ gradient for ATP synthesis) or have demonstrated that the pH may not account for the activities attributed to membrane "energization." Taken together, the observations suggest that there may be specific proton-conducting pathways in or on such energy-transducing membranes that allow them to carry out energy transduction without necessarily involving a pH gradient across the membrane.…”

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confidence: 99%

Anionic lipid headgroups as a proton-conducting pathway along the surface of membranes: a hypothesis.

Haines¹

1983

Proc. Natl. Acad. Sci. U.S.A.

218

167

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Evidence has been gathering from several laboratories that protons in proton-pumping membranes move along or within the bilayer rather than exchange with the bulk phase. These experiments are typically conducted on the natural membrane in vivo or in vitro or on fragments of natural membrane. Anionic lipids are present in all proton-pumping membranes. Model studies on the protonation state of the fatty acids of liposomes containing entrapped water show that the bilayers always contain mixtures of protonated and deprotonated carboxylates. Protonated fatty acids form stable acid-anion pairs with deprotonatedfatty acids through unusually strong hydrogen bonds. Such acid-anion dimers have a single negative charge, which is shared by the four negative oxygens of both headgroups. The two pK values of the resulting dimer will be significantly different from the pK of the monomeric species, so that the dimer will be stable over a wide pH range. It is proposed that anionic lipid headgroups in biological membranes share protons as acid-anion dimers and that anionic lipids thus trap and conduct protons along the headgroup domain of bilayers that contain such anionic lipids-. Protons pumped from the other side ofthe membrane may enter and move within the headgroup sheet because the protonation rate of negatively charged proton acceptors is 5 orders of magnitude faster than that of water. Protons trapped in the acidic headgroup sheet need not leave this region in order to be utilized by a responsive proton-translocating pore (a transport protein using the proton gradient). Experiments suggest the proton concentration in the headgroup domain may vary widely and the anionic lipid headgroup sheet may therefore function as a proton buffer. -Due to the Gouy-Chapman-Stern layer at polyanionic surfaces, anionic lipids will also sequester protons from the bulk solution at low and moderate ionic strengths. At high ionic strength metal cations may replace protons sequestered near the headgroups, but these cations cannot substitute for protons in the "proton-conducting pathway," which is based on hydrogen bonding.Recent experiments in several laboratories have suggested that protons that are translocated by proton-pumping membranes, such as those of mitochondria and halobacteria, need not enter the external bulk water phase in order to be utilized by protontransporting proteins ofthe membrane, such as ATP synthetase. Notable among these experiments are -those of Michel and Oesterhelt (1), who made careful measurements of proton-dependent ATP synthesis and pH changes in and near illuminated, Halobacterium halobium cells. They found, that the pH is not lowered in the bulk aqueous phase as the protons pumped.by the purple patches of bacteriorhodopsin are utilized by ATP synthetase, which is not present in the purple patches but is found at some distance in red patches ofthe same plasma membrane. They concluded that.the protons do not pass through the bulk aqueous phase but move very close to the membrane surface. This system is un...

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The Mitochondrial Membrane Potential

Cited by 51 publications

References 161 publications

On the Mode of Action of the Bacteriocin Butyricin 7423. Effects on Membrane Potential and Potassium-Ion Accumulation in Clostridium pasteurianum

On the Mode of Action of the Bacteriocin Butyricin 7423. Effects on Membrane Potential and Potassium-Ion Accumulation in Clostridium pasteurianum

The mitochondrial permeability transition in neurologic disease

Anionic lipid headgroups as a proton-conducting pathway along the surface of membranes: a hypothesis.

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