Conformational basis of energy transduction in membrane systems VIII. Configurational changes of mitochondria

Williams, Charles H.; Vail, William J.; Harris, Robert A.; Caldwell, Monya; Green, David E.; Valdivia, Enrique

doi:10.1007/bf01515979

Cited by 43 publications

(8 citation statements)

References 22 publications

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“…Prolonged incubation in State 4 results in the appearance of a greater number of mitochondria with swollen matrix and disappearance of the twisted form. These results confirm the reports of Green and coworkers (7)(8)(9)(10)(11)(12) as to the conditions necessary to establish the energlzed-twisted configuration. It is of interest to note, however, that these are also the conditions which support the spontaneous accumulation of monovalent cations and phosphate (21)(22)(23)(24).…”

Section: Resultssupporting

confidence: 92%

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On the "Energized-Twisted" Configuration of Isolated Beef Heart Mitochondria

Hunter

Brierley

1971

The Journal of Cell Biology

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Section: Resultssupporting

confidence: 92%

“…A similar reversible expansion of the matrix of liver mitochondria has been reported by Hackenbrock (4-6). Green and coworkers (7)(8)(9)(10)(11)(12) have noted that the matrix of heart mitochondria expands slightly during respiration in the absence of Pi and have designated this form the "energized" configuration.…”

mentioning

confidence: 99%

On the "Energized-Twisted" Configuration of Isolated Beef Heart Mitochondria

Hunter

Brierley

1971

The Journal of Cell Biology

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“…We did observe, however, that Type II cells often contained large, “atypical” mitochondria that were located only at close appositions between the membranes of Type II cells and P2X2-LIR nerve processes (Figure 5). The cristae of the atypical mitochondria exhibit a “twisted-energized” or “swollen twisted-energized configuration” [50-53], resembling electron-dense sacs or tubules within the mitochondrion (Figures 5A and B). This contrasts with the typical mitochondria distributed throughout the cytoplasm of Type II taste cells, which are elongate, slender structures rarely exceeding 0.3 μm in width and possessing lamellar or baffle cristae (e.g., “m” in Figure 5B).…”

Section: Resultsmentioning

confidence: 99%

“…The atypical mitochondria that we have observed have diameters two to three times larger than conventional mitochondria. Typically the cristae of the atypical mitochondria exhibit a “twisted-energized” or “swollen twisted-energized configuration” [50,51,53], resembling electron-dense sacs or tubules within the mitochondrion. The outer membranes of these atypical mitochondria are closely apposed to the cytoplasmic leaflet of the Type II taste cell’s membrane (Figure 5).…”

Section: Discussionmentioning

confidence: 99%

Immunocytochemical analysis of P2X2 in rat circumvallate taste buds

et al. 2012

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BackgroundOur laboratory has shown that classical synapses and synaptic proteins are associated with Type III cells. Yet it is generally accepted that Type II cells transduce bitter, sweet and umami stimuli. No classical synapses, however, have been found associated with Type II cells. Recent studies indicate that the ionotropic purinergic receptors P2X2/P2X3 are present in rodent taste buds. Taste nerve processes express the ionotropic purinergic receptors (P2X2/P2X3). P2X2/P2X3Dbl−/− mice are not responsive to sweet, umami and bitter stimuli, and it has been proposed that ATP acts as a neurotransmitter in taste buds. The goal of the present study is to learn more about the nature of purinergic contacts in rat circumvallate taste buds by examining immunoreactivity to antisera directed against the purinergic receptor P2X2.ResultsP2X2-like immunoreactivity is present in intragemmal nerve processes in rat circumvallate taste buds. Intense immunoreactivity can also be seen in the subgemmal nerve plexuses located below the basal lamina. The P2X2 immunoreactive nerve processes also display syntaxin-1-LIR. The immunoreactive nerves are in close contact with the IP3R3-LIR Type II cells and syntaxin-1-LIR and/or 5-HT-LIR Type III cells. Taste cell synapses are observed only from Type III taste cells onto P2X2-LIR nerve processes. Unusually large, “atypical” mitochondria in the Type II taste cells are found only at close appositions with P2X2-LIR nerve processes. P2X2 immunogold particles are concentrated at the membranes of nerve processes at close appositions with taste cells.ConclusionsBased on our immunofluorescence and immunoelectron microscopical studies we believe that both perigemmal and most all intragemmal nerve processes display P2X2-LIR. Moreover, colloidal gold immunoelectron microscopy indicates that P2X2-LIR in nerve processes is concentrated at sites of close apposition with Type II cells. This supports the hypothesis that ATP may be a key neurotransmitter in taste transduction and that Type II cells release ATP, activating P2X2 receptors in nerve processes.

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“…The appeal of the conformational model extends beyond the experimental evidence that has until now been introduced in support of it (7)(8)(9). The requirement for an intermediate energy form that can be coupled with electron transfer, ATP synthesis or hydrolysis, and ion translocation requires a certain versatility for which a metastable protein conformation would appear to be singularly well suited (10,11).…”

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confidence: 99%

Conformational Model of Active Transport: Role of Protons

Young

Blondin

Green

1971

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

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A conformational model of monovalent cation transport in mitochondria is described. Because it incorporates the proton-generated membrane potential and pH differential of the chemiosmotic model, the model successfully rationalizes a wide variety of mitochondrial ion-transport phenomena.The active transport of alkali metal cations in the mitochondrion can be greatly enhanced by exogenous ionophores. Thus the very same reagents that facilitate the passive transport of alkali metal cations through biological membranes and lipid bilayers also enhance their active transport. This strongly suggests that the same mechanism of permeation applies under both active and passive transport conditions.There are two types of ionophores, the neutral and the monocarboxylate or anionic ionophores (1, 2), and it has now been demonstrated that both types induce a form of active transport across the inner mitochondrial membrane (3, 4). The two types of ionophore induce two distinct types of active transport, each with its particular characteristics.Montal et al. (4) We have recently proposed a model of active transport that rests upon two fundamental assumptions: (i) there is a cycle of conformational change in the transduction of chemical free energy into the free energy of an ion gradient, and (ii) the physicochemical properties of the ionophores require that the movement of ions be spontaneously down local electrochemical potential gradients (6). However, the development of the model based on these two assumptions was very inadequate. The most obvious inadequacy was that it required the completely untenable binding of a large number of weak acid anions on the inner surface of the inner mitochondrial membrane. Furthermore, it did not involve in any intrinsic manner a cyclical conformational change, despite the fact that a cycle of conformational change was one of the basic postulates.

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Conformational basis of energy transduction in membrane systems VIII. Configurational changes of mitochondria

Cited by 43 publications

References 22 publications

On the "Energized-Twisted" Configuration of Isolated Beef Heart Mitochondria

On the "Energized-Twisted" Configuration of Isolated Beef Heart Mitochondria

Immunocytochemical analysis of P2X2 in rat circumvallate taste buds

Conformational Model of Active Transport: Role of Protons

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