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Electrochemical gradient

About: Electrochemical gradient is a research topic. Over the lifetime, 3175 publications have been published within this topic receiving 140054 citations.


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Journal ArticleDOI
TL;DR: It has been suggested that the permeability transition and its reversal may also function as a mitochondrial Ca2+ efflux mechanism under some conditions.
Abstract: It has been firmly established that the rapid uptake of Ca2+ by mitochondria from a wide range of sources is mediated by a uniporter which permits transport of the ion down its electrochemical gradient. Several mechanisms of Ca2+ efflux from mitochondria have also been extensively discussed in the literature. Energized mitochondria must expend a significant amount of energy to transport Ca2+ against its electrochemical gradient from the matrix space to the external space. Two separate mechanisms have been found to mediate this outward transport: a Ca2+/nNa+ exchanger and a Na(+)-independent efflux mechanism. These efflux mechanisms are considered from the perspective of available energy. In addition, a reversible Ca2(+)-induced increase in inner membrane permeability can also occur. The induction of this permeability transition is characterized by swelling of the mitochondria, leakiness to small ions such as K+, Mg2+, and Ca2+, and loss of the mitochondrial membrane potential. It has been suggested that the permeability transition and its reversal may also function as a mitochondrial Ca2+ efflux mechanism under some conditions. The characteristics of each of these mechanisms are discussed, as well as their possible physiological functions.

1,599 citations

Journal ArticleDOI
22 Jan 2004-Nature
TL;DR: By patch-clamping the inner mitochondrial membrane, it is concluded that the properties of the current mediated by this novel channel are those of the MCU, enabling high Ca2+ selectivity despite relatively low cytoplasmic Ca 2+ concentrations.
Abstract: During intracellular Ca2+ signalling mitochondria accumulate significant amounts of Ca2+ from the cytosol. Mitochondrial Ca2+ uptake controls the rate of energy production, shapes the amplitude and spatio-temporal patterns of intracellular Ca2+ signals, and is instrumental to cell death. This Ca2+ uptake is undertaken by the mitochondrial Ca2+ uniporter (MCU) located in the organelle's inner membrane. The uniporter passes Ca2+ down the electrochemical gradient maintained across this membrane without direct coupling to ATP hydrolysis or transport of other ions. Carriers are characterized by turnover numbers that are typically 1,000-fold lower than ion channels, and until now it has been unclear whether the MCU is a carrier or a channel. By patch-clamping the inner mitochondrial membrane, we identified a previously unknown Ca2+-selective ion channel sensitive to inhibitors of mitochondrial Ca2+ uptake. Our data indicate that this unique channel binds Ca2+ with extremely high affinity (dissociation constant < or =2 nM), enabling high Ca2+ selectivity despite relatively low cytoplasmic Ca2+ concentrations. The channel is inwardly rectifying, making it especially effective for Ca2+ uptake into energized mitochondria. Thus, we conclude that the properties of the current mediated by this novel channel are those of the MCU.

1,315 citations

Journal ArticleDOI
TL;DR: The kinetics for uptake by mitochondria of TPP+ and DDA+ were analyzed, and it was found that TPP+ permeated the mitochondrial membrane about 15 times faster than DDA+.
Abstract: The membrane potential of mitochondria was estimated from the accumulation of tetraphenyl phosphonium (TPP+), which was determined with the TPP+-selective electrode developed in the present study. The preparation and some operational parameters of the electrode were described. The kinetics for uptake by mitochondria of TPP+ and DDA+ (dibenzyldimethyl ammonium) were analyzed, and it was found that TPP+ permeated the mitochondrial membrane about 15 times faster than DDA+. The final amounts of accumulation of TPP+ and DDA+ by mitochondria were approximately equal. For the state-4 mitochondria, the membrane potential was about 180 mV (interior negative). Simultaneous measurements of TPP+-uptake and oxygen consumption showed that the transition between states 3 and 4 was detectable by use of the TPP+-electrode. After the TPP+-electrode showed that state-4 was reached, the extra-mitochondrial phosphorylation potential was measured. The difference in pH across the membrane was measured from the distribution of permeant anion, acetate, so as to calculate the proton electrochemical potential. The ratio of extra-mitochondrial phosphorylation potential to proton electro-chemical potential, n was close to 3. This value of n was also found to be 3 when ATP was hydrolyzed under the condition that the respiratory chain was arrested. The implication that n = 3 was discussed.

938 citations

Journal ArticleDOI
TL;DR: The mechanisms of sodium entry, extrusion, and compartmentation are reviewed, with a discussion of recent progress on the cloning and characterization, directly in planta and in yeast, of some of the proteins involved in sodium transport.

934 citations

Journal ArticleDOI
TL;DR: Preliminary results indicate that the gradient in H. halobium plays the central role in energy coupling attributed to such electrochemical gradients by Mitchell's chemiosmotic theory.
Abstract: The purple membrane of Halobacterium halobium contains only one protein, bacteriorhodopsin, which closely resembles the visual pigments of animals. Light flashes cause a rapid transient shift of its absorption maximum from 560 to 415 nm. This shift is accompanied by release and uptake of protons. Respiring cells acidify the medium in the dark; if they contain purple membrane their O2 consumption is reduced in the light. Starved or anaerobic cells containing purple membrane, in the absence of any apparent source of energy, generate and maintain a proton gradient across the cell membrane as long as they are exposed to light. We postulate that the light-generated proton gradient arises from a vectorial release and uptake of protons by bacteriorhodopsin, which is suitably oriented in the cell membrane and under continuous illumination oscillates rapidly between the long- and short-wavelength form. Preliminary results indicate that the gradient in H. halobium plays the central role in energy coupling attributed to such electrochemical gradients by Mitchell's chemiosmotic theory.

932 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202325
202259
202133
202038
201929
201844