Potassium Collapses the ΔPin Yeast Mitochondria While the Rate of ATP Synthesis Is Inhibited Only Partially: Modulation by Phosphate

Castrejón, Vicente; Parra, Carlos; Moreno, Rafael; Peña, Antonio; Uribe, Salvador

doi:10.1006/abbi.1997.0273

Cited by 26 publications

(23 citation statements)

References 36 publications

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“…The reason why a time limit to the recovery went unnoticed in a previous study is probably that in those experiments phosphate was added within 30 s after the addition of ethanol (24).…”

Section: Discussionmentioning

confidence: 91%

Phosphate Is Required to Maintain the Outer Membrane Integrity and Membrane Potential of Respiring Yeast Mitochondria

Janssen

Kruijff

Kroon

2002

Analytical Biochemistry

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“…The reason why a time limit to the recovery went unnoticed in a previous study is probably that in those experiments phosphate was added within 30 s after the addition of ethanol (24).…”

Section: Discussionmentioning

confidence: 91%

Phosphate Is Required to Maintain the Outer Membrane Integrity and Membrane Potential of Respiring Yeast Mitochondria

Janssen

Kruijff

Kroon

2002

Analytical Biochemistry

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“…The membrane potential was estimated from the accumulation ratio, after subtracting TPMP accumulation measured in a parallel incubation containing 4 M carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone (FCCP), and assuming a mitochondrial volume of 0.7 l per mg of protein (3). Protein concentration was assayed by the bicinchoninic acid (BCA) method (Pierce) with bovine serum albumin as the standard.…”

Section: Methodsmentioning

confidence: 99%

Tim18p, a New Subunit of the TIM22 Complex That Mediates Insertion of Imported Proteins into the Yeast Mitochondrial Inner Membrane

Koehler¹,

Murphy²,

Bally

et al. 2000

Molecular and Cellular Biology

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Import of carrier proteins from the cytoplasm into the mitochondrial inner membrane of yeast is mediated by a distinct system consisting of two soluble 70-kDa protein complexes in the intermembrane space and a 300-kDa complex in the inner membrane, the TIM22 complex. The TIM22 complex contains the peripheral subunits Tim9p, Tim10p, and Tim12p and the integral membrane subunits Tim22p and Tim54p. We identify here an additional subunit, an 18-kDa integral membrane protein termed Tim18p. This protein is made as a 21.9-kDa precursor which is imported into mitochondria and processed to its mature form. When mitochondria are gently solubilized, Tim18p comigrates with the other subunits of the TIM22 complex on nondenaturing gels and is coimmunoprecipitated with Tim54p and Tim12p. Tim18p does not cofractionate with the TIM23 complex upon immunoprecipitation or nondenaturing gel electrophoresis. Deletion of Tim18p decreases the growth rate of yeast cells by a factor of two and is synthetically lethal with temperature-sensitive mutations in Tim9p or Tim10p. It also impairs the import of several precursor proteins into isolated mitochondria, and lowers the apparent mass of the TIM22 complex. We suggest that Tim18p functions in the assembly and stabilization of the TIM22 complex but does not directly participate in protein insertion into the inner membrane.Most mitochondrial proteins are synthesized in the cytosol with a cleavable N-terminal presequence that specifies import into mitochondria via the general protein import pathway (25,27,32,36). This pathway is mediated by cytosolic chaperones, a hetero-oligomeric TOM complex in the mitochondrial outer membrane, a Tim17p-Tim23p complex (referred to as the TIM23 complex) in the inner membrane, an ATP-dependent import motor associated with the matrix face of the TIM23 complex, and soluble proteins in the matrix involved in the proteolytic maturation and folding of the imported proteins (9,11,(27)(28)(29).Over the past few years it has become clear that mitochondria possess an additional pathway which affects import of hydrophobic inner membrane proteins (17,22,27). This pathway diverges from the general import pathway after the TOM channel (23). As the hydrophobic precursor exits that channel, it is met by one of the two soluble 70-kDa protein complexes that transfer it across the intermembrane space (1,19,21,39). One of these 70-kDa complexes contains Tim9p and Tim10p, while the other contains Tim8p and Tim13p (20). Both complexes generally deliver hydrophobic proteins to an inner membrane complex specialized for the insertion of membrane proteins. This insertion complex, referred to as the TIM22 complex, has an apparent mass of 300 kDa and contains the membrane proteins Tim22p and Tim54p, the peripheral membrane protein Tim12p, and a small proportion of Tim9p and Tim10p (1,18,19,21,39). The 70-kDa Tim9p-Tim10p complex can also deliver some membrane proteins to the TIM23 complex and, possibly, to additional, as-yet-unknown insertion sites (24).A typical protein imported by ...

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“…(18) showed that, for the same respiration rate, Δp was lesser in a KCl medium than in sucrose medium, but the ratio between the amount of phosphorylated ADP and oxygen consumed (ADP/O) did not vary. In respiring yeast mitochondria, addition of KCl in the presence of 4-5 mM phosphate generated some potassium cycle through electrophoretic K + entry and electroneutral K + /H + exchange without promoting any uncoupling between respiration and ATP synthesis, but even increasing ATP synthesis on the basis of a compensatory ΔpH increase that drives the activation of phosphate/H + cotransporter (19,20). On the other hand, Castrejón et al .…”

Section: The Effect Of Pmitokatp On the Mitochondrial Protonmotive Fomentioning

confidence: 99%

“…On the other hand, Castrejón et al . (20) and Manon and Guérin (21) showed that at low phosphate concentration (0.4-0.5 mM), mitochondrial uncoupling by KCl occurred with collapse of Δp and dramatic reduction of ADP/O and respiratory control (RC) ratios, as well as of ATP synthesis rate (about -65% than in high phosphate).…”

Section: The Effect Of Pmitokatp On the Mitochondrial Protonmotive Fomentioning

confidence: 99%

The uniqueness of the plant mitochondrial potassium channel

Pastore

Soccio²,

Laus³

et al. 2013

BMB Reports

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The ATP-inhibited Plant Mitochondrial K+ Channel (PmitoKATP) was discovered about fifteen years ago in Durum Wheat Mitochondria (DWM). PmitoKATP catalyses the electrophoretic K+ uniport through the inner mitochondrial membrane; moreover, the co-operation between PmitoKATP and +/H+ antiporter allows such a great operation of a K+ cycle to collapse mitochondrial membrane potential (ΔΨ) and ΔpH, thus impairing protonmotive force (Δp). A possible physiological role of such ΔΨ control is the restriction of harmful reactive oxygen species (ROS) production under environmental/oxidative stress conditions. Interestingly, DWM lacking Δp were found to be nevertheless fully coupled and able to regularly accomplish ATP synthesis; this unexpected behaviour makes necessary to recast in some way the classical chemiosmotic model. In the whole, PmitoKATP may oppose to large scale ROS production by lowering ΔΨ under environmental/oxidative stress, but, when stress is moderate, this occurs without impairing ATP synthesis in a crucial moment for cell and mitochondrial bioenergetics. [BMB Reports 2013; 46(8): 391-397]

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Potassium Collapses the ΔPin Yeast Mitochondria While the Rate of ATP Synthesis Is Inhibited Only Partially: Modulation by Phosphate

Cited by 26 publications

References 36 publications

Phosphate Is Required to Maintain the Outer Membrane Integrity and Membrane Potential of Respiring Yeast Mitochondria

Phosphate Is Required to Maintain the Outer Membrane Integrity and Membrane Potential of Respiring Yeast Mitochondria

Tim18p, a New Subunit of the TIM22 Complex That Mediates Insertion of Imported Proteins into the Yeast Mitochondrial Inner Membrane

The uniqueness of the plant mitochondrial potassium channel

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