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Naima J, Ohta Y. Potassium Ions Decrease Mitochondrial Matrix pH: Implications for ATP Production and Reactive Oxygen Species Generation. Int J Mol Sci 2024; 25:1233. [PMID: 38279231 PMCID: PMC10815940 DOI: 10.3390/ijms25021233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2023] [Revised: 01/05/2024] [Accepted: 01/14/2024] [Indexed: 01/28/2024] Open
Abstract
Potassium (K+) is the most abundant cation in the cytosol and is maintained at high concentrations within the mitochondrial matrix through potassium channels. However, many effects of K+ at such high concentrations on mitochondria and the underlying mechanisms remain unclear. This study aims to elucidate these effects and mechanisms by employing fluorescence imaging techniques to distinguish and precisely measure signals inside and outside the mitochondria. We stained the mitochondrial matrix with fluorescent dyes sensitive to K+, pH, reactive oxygen species (ROS), and membrane potential in plasma membrane-permeabilized C6 cells and isolated mitochondria from C6 cells. Fluorescence microscopy facilitated the accurate measurement of fluorescence intensity inside and outside the matrix. Increasing extramitochondrial K+ concentration from 2 mM to 127 mM led to a reduction in matrix pH and a decrease in the generation of highly reactive ROS. In addition, elevated K+ levels electrically polarized the inner membrane of the mitochondria and promoted efficient ATP synthesis via FoF1-ATPase. Introducing protons (H+) into the matrix through phosphate addition led to further mitochondrial polarization, and this effect was more pronounced in the presence of K+. K+ at high concentrations, reaching sub-hundred millimolar levels, increased H+ concentration within the matrix, suppressing ROS generation and boosting ATP synthesis. Although this study does not elucidate the role of specific types of potassium channels in mitochondria, it does suggest that mitochondrial K+ plays a beneficial role in maintaining cellular health.
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Affiliation(s)
| | - Yoshihiro Ohta
- Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Nakacho, Koganei, Tokyo 184-8588, Japan;
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2
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Li D, Huang M, Dong S, Jin Y, Zhou R, Wu C. Comprehensive Transcriptomic Analysis of Heterotrophic Nitrifying Bacterium Klebsiella sp. TN-10 in Response to Nitrogen Stress. Microorganisms 2022; 10:microorganisms10020353. [PMID: 35208807 PMCID: PMC8876665 DOI: 10.3390/microorganisms10020353] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 01/28/2022] [Accepted: 01/31/2022] [Indexed: 02/01/2023] Open
Abstract
Klebsiella sp. TN-10, a heterotrophic nitrifying bacterium, showed excellent nitrification ability under nitrogen stress. The strain was cultured under different nitrogen stress levels, including ammonium sulfate 0.5, 2.5, and 5 g/L, and samples were titled group-L, group-M, and group-H, respectively. In these three groups, the removed total nitrogen was 70.28, 118.33, and 157.18 mg/L after 12 h of cultivation, respectively. An RNA-Seq transcriptome analysis was used to describe key regulatory networks in response to nitrogen stress. The GO functional enrichment and KEGG enrichment analyses showed that differentially expressed genes (DEGs) participated in more pathways under higher nitrogen stress (group-H). Carbohydrate metabolism and amino acid metabolism were the most abundant subcategories, which meant these pathways were significantly influenced by nitrogen stress and could be related to nitrogen removal. In the nitrogen cycle, up-regulated gene2311 (narK, encodes major facilitator superfamily transporter) may accelerate the entry of nitrogen into the cells and subsequently contribute to the nitrogen utilization. In addition, the up-regulation of gene2312 (narG), gene2313 (narH), and gene2315 (narH) may accelerate denitrification pathways and facilitate nitrogen removal. The results presented in this study may play a pivotal role in understanding the regulation networks of the nitrifying bacterium TN-10 under nitrogen stress.
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Affiliation(s)
- Dan Li
- College of Biomass Science and Engineering, Sichuan University, Chengdu 610065, China; (D.L.); (Y.J.); (R.Z.)
| | - Mingquan Huang
- Beijing Laboratory of Food Quality and Safety, Beijing Technology and Business University, Beijing 100048, China
- Correspondence: (M.H.); (C.W.)
| | - Shirong Dong
- Sichuan Fansaoguang Food Group Co., Ltd, Chengdu 611732, China;
| | - Yao Jin
- College of Biomass Science and Engineering, Sichuan University, Chengdu 610065, China; (D.L.); (Y.J.); (R.Z.)
| | - Rongqing Zhou
- College of Biomass Science and Engineering, Sichuan University, Chengdu 610065, China; (D.L.); (Y.J.); (R.Z.)
| | - Chongde Wu
- College of Biomass Science and Engineering, Sichuan University, Chengdu 610065, China; (D.L.); (Y.J.); (R.Z.)
- Correspondence: (M.H.); (C.W.)
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Morales-García L, Ricardez-García C, Castañeda-Tamez P, Chiquete-Félix N, Uribe-Carvajal S. Coupling/Uncoupling Reversibility in Isolated Mitochondria from Saccharomyces cerevisiae. Life (Basel) 2021; 11:life11121307. [PMID: 34947838 PMCID: PMC8707985 DOI: 10.3390/life11121307] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Revised: 11/16/2021] [Accepted: 11/22/2021] [Indexed: 12/13/2022] Open
Abstract
The yeast Saccharomyces cerevisiae uses fermentation as the preferred pathway to obtain ATP and requires the respiratory chain to re-oxidize the NADH needed for activity of Glyceraldehyde-3-phosphate. This process is favored by uncoupling of oxidative phosphorylation (OxPhos), which is at least partially controlled by the mitochondrial unspecific pore (ScMUC). When mitochondrial ATP synthesis is needed as in the diauxic phase or during mating, a large rise in Ca2+ concentration ([Ca2+]) closes ScMUC, coupling OxPhos. In addition, ScMUC opening/closing is mediated by the ATP/ADP ratio, which indicates cellular energy needs. Here, opening and closing of ScMUC was evaluated in isolated mitochondria from S. cerevisiae at different incubation times and in the presence of different ATP/ADP ratios or varying [Ca2+]. Measurements of the rate of O2 consumption, mitochondrial swelling, transmembrane potential and ROS generation were conducted. It was observed that ScMUC opening was reversible, a high ATP/ADP ratio promoted opening and [Ca2+] closed ScMUC even after several minutes of incubation in the open state. In the absence of ATP synthesis, closure of ScMUC resulted in an increase in ROS.
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Affiliation(s)
- Lilia Morales-García
- Department of Genetics and Molecular Biology, Instituto de Fisiología Celular, UNAM, Mexico City 04510, Mexico; (L.M.-G.); (C.R.-G.); (P.C.-T.); (N.C.-F.)
- Department of Biochemistry, Medicine School, UNAM, Mexico City 04510, Mexico
| | - Carolina Ricardez-García
- Department of Genetics and Molecular Biology, Instituto de Fisiología Celular, UNAM, Mexico City 04510, Mexico; (L.M.-G.); (C.R.-G.); (P.C.-T.); (N.C.-F.)
| | - Paulina Castañeda-Tamez
- Department of Genetics and Molecular Biology, Instituto de Fisiología Celular, UNAM, Mexico City 04510, Mexico; (L.M.-G.); (C.R.-G.); (P.C.-T.); (N.C.-F.)
| | - Natalia Chiquete-Félix
- Department of Genetics and Molecular Biology, Instituto de Fisiología Celular, UNAM, Mexico City 04510, Mexico; (L.M.-G.); (C.R.-G.); (P.C.-T.); (N.C.-F.)
| | - Salvador Uribe-Carvajal
- Department of Genetics and Molecular Biology, Instituto de Fisiología Celular, UNAM, Mexico City 04510, Mexico; (L.M.-G.); (C.R.-G.); (P.C.-T.); (N.C.-F.)
- Department of Biochemistry, Medicine School, UNAM, Mexico City 04510, Mexico
- Correspondence: ; Tel.: +52-5555625632
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Yao S, Zhou R, Jin Y, Huang J, Wu C. Effect of co-culture with Tetragenococcus halophilus on the physiological characterization and transcription profiling of Zygosaccharomyces rouxii. Food Res Int 2019; 121:348-358. [PMID: 31108757 DOI: 10.1016/j.foodres.2019.03.053] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 03/13/2019] [Accepted: 03/25/2019] [Indexed: 12/16/2022]
Abstract
Zygosaccharomyces rouxii and Tetragenococcus halophilus are widely existed and play vital roles during the manufacture of fermented foods such as soy sauce. The aim of this study was to elucidate the effect of T. halophilus CGMCC 3792 on the physiological characterizations and transcription profiling of Z. rouxii CGMCC 3791. Salt tolerance analysis revealed that co-culture with T. halophilus enhanced the salt tolerance of Z. rouxii during salt stress. Analysis of the volatile compounds revealed that co-culture reduced the level of 1-butanol, improved the level of octanoic acid which all were produced by T. halophilus and reduced the level of phenylethyl alcohol produced by Z. rouxii. The presence of Z. rouxii decreased the contents of 3,4-dimethylbenzaldehyde and acetic acid produced by T. halophilus. In addition, co-culture improved the content of benzyl alcohol significantly. Analysis of membrane fatty acid showed that co-culture improved the content of palmitic (C16:0) and stearic (C18:0) acids in cells of Z. rouxii, and reduced the contents of myristic (C14:0), palmitoleic acid (C16:1) and oleic acid (C18:1). In order to further explore the interactions between the two strains, RNA-seq technology was used to investigate the effect of co-culture with T. halophilus on the transcription profiling of Z. rouxii. By comparing cells incubated in co-culture group with cells incubated in single-culture group, a total of 967 genes were considered as differentially expressed genes (DEGs). Among the DEGs, 72 genes were up-regulated, while 895 genes were down-regulated. These DEGs took party in various activities in cells of Z. rouxii, and the result showed co-culture with T. halophilus had a positive effect on proteolysis, the attachment of a cell to another cell, extracellular protein accumulation, energy metabolism, and a negative effect on oxidative phosphorylation, small molecular substances metabolism, DNA replication and repair, and transcription in cells of Z. rouxii. Results presented in this study may contribute to further understand the interactions between Zygosaccharomyces rouxii and Tetragenococcus halophilus.
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Affiliation(s)
- Shangjie Yao
- College of Light Industry, Textile & Food Engineering, Sichuan University, Chengdu 610065, China; Key Laboratory of Leather Chemistry and Engineering, Ministry of Education, Sichuan University, Chengdu 610065, China
| | - Rongqing Zhou
- College of Light Industry, Textile & Food Engineering, Sichuan University, Chengdu 610065, China; Key Laboratory of Leather Chemistry and Engineering, Ministry of Education, Sichuan University, Chengdu 610065, China
| | - Yao Jin
- College of Light Industry, Textile & Food Engineering, Sichuan University, Chengdu 610065, China; Key Laboratory of Leather Chemistry and Engineering, Ministry of Education, Sichuan University, Chengdu 610065, China
| | - Jun Huang
- College of Light Industry, Textile & Food Engineering, Sichuan University, Chengdu 610065, China; Key Laboratory of Leather Chemistry and Engineering, Ministry of Education, Sichuan University, Chengdu 610065, China
| | - Chongde Wu
- College of Light Industry, Textile & Food Engineering, Sichuan University, Chengdu 610065, China; Key Laboratory of Leather Chemistry and Engineering, Ministry of Education, Sichuan University, Chengdu 610065, China.
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Trono D, Laus MN, Soccio M, Alfarano M, Pastore D. Modulation of Potassium Channel Activity in the Balance of ROS and ATP Production by Durum Wheat Mitochondria-An Amazing Defense Tool Against Hyperosmotic Stress. FRONTIERS IN PLANT SCIENCE 2015; 6:1072. [PMID: 26648958 PMCID: PMC4664611 DOI: 10.3389/fpls.2015.01072] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 11/16/2015] [Indexed: 05/03/2023]
Abstract
In plants, the existence of a mitochondrial potassium channel was firstly demonstrated about 15 years ago in durum wheat as an ATP-dependent potassium channel (PmitoKATP). Since then, both properties of the original PmitoKATP and occurrence of different mitochondrial potassium channels in a number of plant species (monocotyledonous and dicotyledonous) and tissues/organs (etiolated and green) have been shown. Here, an overview of the current knowledge is reported; in particular, the issue of PmitoKATP physiological modulation is addressed. Similarities and differences with other potassium channels, as well as possible cross-regulation with other mitochondrial proteins (Plant Uncoupling Protein, Alternative Oxidase, Plant Inner Membrane Anion Channel) are also described. PmitoKATP is inhibited by ATP and activated by superoxide anion, as well as by free fatty acids (FFAs) and acyl-CoAs. Interestingly, channel activation increases electrophoretic potassium uptake across the inner membrane toward the matrix, so collapsing membrane potential (ΔΨ), the main component of the protonmotive force (Δp) in plant mitochondria; moreover, cooperation between PmitoKATP and the K(+)/H(+) antiporter allows a potassium cycle able to dissipate also ΔpH. Interestingly, ΔΨ collapse matches with an active control of mitochondrial reactive oxygen species (ROS) production. Fully open channel is able to lower superoxide anion up to 35-fold compared to a condition of ATP-inhibited channel. On the other hand, ΔΨ collapse by PmitoKATP was unexpectedly found to not affect ATP synthesis via oxidative phosphorylation. This may probably occur by means of a controlled collapse due to ATP inhibition of PmitoKATP; this brake to the channel activity may allow a loss of the bulk phase Δp, but may preserve a non-classically detectable localized driving force for ATP synthesis. This ability may become crucial under environmental/oxidative stress. In particular, under moderate hyperosmotic stress (mannitol or NaCl), PmitoKATP was found to be activated by ROS, so inhibiting further large-scale ROS production according to a feedback mechanism; moreover, a stress-activated phospholipase A2 may generate FFAs, further activating the channel. In conclusion, a main property of PmitoKATP is the ability to keep in balance the control of harmful ROS with the mitochondrial/cellular bioenergetics, thus preserving ATP for energetic needs of cell defense under stress.
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Affiliation(s)
- Daniela Trono
- Consiglio per la Ricerca in Agricoltura e l’Analisi dell’Economia Agraria, Centro di Ricerca per la Cerealicoltura, Foggia, Italy
| | - Maura N. Laus
- Dipartimento di Scienze Agrarie, degli Alimenti e dell’Ambiente, Università di Foggia, Foggia, Italy
| | - Mario Soccio
- Dipartimento di Scienze Agrarie, degli Alimenti e dell’Ambiente, Università di Foggia, Foggia, Italy
| | - Michela Alfarano
- Dipartimento di Scienze Agrarie, degli Alimenti e dell’Ambiente, Università di Foggia, Foggia, Italy
| | - Donato Pastore
- Dipartimento di Scienze Agrarie, degli Alimenti e dell’Ambiente, Università di Foggia, Foggia, Italy
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Cabrera-Orefice A, Ibarra-García-Padilla R, Maldonado-Guzmán R, Guerrero-Castillo S, Luévano-Martínez LA, Pérez-Vázquez V, Gutiérrez-Aguilar M, Uribe-Carvajal S. The Saccharomyces cerevisiae mitochondrial unselective channel behaves as a physiological uncoupling system regulated by Ca2+, Mg2+, phosphate and ATP. J Bioenerg Biomembr 2015; 47:477-91. [PMID: 26530988 DOI: 10.1007/s10863-015-9632-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 10/23/2015] [Indexed: 02/07/2023]
Abstract
It is proposed that the Saccharomyces cerevisiae the Mitochondrial Unselective Channel ((Sc)MUC) is tightly regulated constituting a physiological uncoupling system that prevents overproduction of reactive oxygen species (ROS). Mg(2+), Ca(2+) or phosphate (Pi) close (Sc)MUC, while ATP or a high rate of oxygen consumption open it. We assessed (Sc)MUC activity by measuring in isolated mitochondria the respiratory control, transmembrane potential (ΔΨ), swelling and production of ROS. At increasing [Pi], less [Ca(2+)] and/or [Mg(2+)] were needed to close (Sc)MUC or increase ATP synthesis. The Ca(2+)-mediated closure of (Sc)MUC was prevented by high [ATP] while the Mg(2+) or Pi effect was not. When Ca(2+) and Mg(2+) were alternatively added or chelated, (Sc)MUC opened and closed reversibly. Different effects of Ca(2+) vs Mg(2+) effects were probably due to mitochondrial Mg(2+) uptake. Our results suggest that (Sc)MUC activity is dynamically controlled by both the ATP/Pi ratio and divalent cation fluctuations. It is proposed that the reversible opening/closing of (Sc)MUC leads to physiological uncoupling and a consequent decrease in ROS production.
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Affiliation(s)
- Alfredo Cabrera-Orefice
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Rodrigo Ibarra-García-Padilla
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Rocío Maldonado-Guzmán
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | | | - Luis A Luévano-Martínez
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil
| | | | | | - Salvador Uribe-Carvajal
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico. .,Salvador Uribe-Carvajal, Department of Molecular Genetics, Instituto de Fisiología Celular, UNAM, Apdo. postal 70-242, 04510, Mexico City, Mexico.
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Bradshaw PC, Pfeiffer DR. Characterization of the respiration-induced yeast mitochondrial permeability transition pore. Yeast 2014; 30:471-83. [PMID: 24166770 DOI: 10.1002/yea.2984] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Revised: 09/29/2013] [Accepted: 10/17/2013] [Indexed: 11/11/2022] Open
Abstract
When isolated mitochondria from the yeast Saccharomyces cerevisiae oxidize respiratory substrates in the absence of phosphate and ADP, the yeast mitochondrial unselective channel, also called the yeast permeability transition pore (yPTP), opens in the inner membrane, dissipating the electrochemical gradient. ATP also induces yPTP opening. yPTP opening allows mannitol transport into isolated mitochondria of laboratory yeast strains, but mannitol is not readily permeable through the yPTP in an industrial yeast strain, Yeast Foam. The presence of oligomycin, an inhibitor of ATP synthase, allowed for respiration-induced mannitol permeability in mitochondria from this strain. Potassium (K+) had varied effects on the respiration-induced yPTP, depending on the concentration of the respiratory substrate added. At low respiratory substrate concentrations K+ inhibited respiration-induced yPTP opening, while at high substrate concentrations this effect diminished. However, at the high respiratory substrate concentrations, the presence of K+ partially prevented phosphate inhibition of yPTP opening. Phosphate was found to inhibit respiration-induced yPTP opening by binding a site on the matrix space side of the inner membrane in addition to its known inhibitory effect of donating protons to the matrix space to prevent the pH change necessary for yPTP opening. The respiration-induced yPTP was also inhibited by NAD, Mg2+, NH4 + or the oxyanion vanadate polymerized to decavanadate. The results demonstrate similar effectors of the respiration-induced yPTP as those previously described for the ATP-induced yPTP and reconcile previous strain-dependent differences in yPTP solute selectivity.
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Rosas-Lemus M, Uribe-Alvarez C, Chiquete-Félix N, Uribe-Carvajal S. In Saccharomyces cerevisiae fructose-1,6-bisphosphate contributes to the Crabtree effect through closure of the mitochondrial unspecific channel. Arch Biochem Biophys 2014; 555-556:66-70. [PMID: 24924491 DOI: 10.1016/j.abb.2014.05.027] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Revised: 05/16/2014] [Accepted: 05/30/2014] [Indexed: 01/15/2023]
Abstract
In Saccharomyces cerevisiae addition of glucose inhibits oxygen consumption, i.e. S. cerevisiae is Crabtree-positive. During active glycolysis hexoses-phosphate accumulate, and probably interact with mitochondria. In an effort to understand the mechanism underlying the Crabtree effect, the effect of two glycolysis-derived hexoses-phosphate was tested on the S. cerevisiae mitochondrial unspecific channel (ScMUC). Glucose-6-phosphate (G6P) promoted partial opening of ScMUC, which led to proton leakage and uncoupling which in turn resulted in, accelerated oxygen consumption. In contrast, fructose-1,6-bisphosphate (F1,6BP) closed ScMUC and thus inhibited the rate of oxygen consumption. When added together, F1,6BP reverted the mild G6P-induced effects. F1,6BP is proposed to be an important modulator of ScMUC, whose closure contributes to the "Crabtree effect".
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Affiliation(s)
- Mónica Rosas-Lemus
- Department of Molecular Genetics, Inst. de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico
| | - Cristina Uribe-Alvarez
- Department of Molecular Genetics, Inst. de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico
| | - Natalia Chiquete-Félix
- Department of Molecular Genetics, Inst. de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico
| | - Salvador Uribe-Carvajal
- Department of Molecular Genetics, Inst. de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico.
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Pastore D, Soccio M, Laus MN, Trono D. The uniqueness of the plant mitochondrial potassium channel. BMB Rep 2013; 46:391-7. [PMID: 23977986 PMCID: PMC4133908 DOI: 10.5483/bmbrep.2013.46.8.075] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Revised: 04/11/2013] [Accepted: 04/11/2013] [Indexed: 01/27/2023] Open
Abstract
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 K(+)/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.
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Affiliation(s)
- Donato Pastore
- Dipartimento di Scienze Agrarie, degli Alimenti e dell'Ambiente, Università di Foggia, Via Napoli 25-71122 Foggia, Italy.
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Palovicova V, Bardelcikova A, Obernauerova M. Absence of anionic phospholipids in Kluyveromyces lactis cells is fatal without F1-catalysed ATP hydrolysis. Can J Microbiol 2012; 58:694-702. [PMID: 22582877 DOI: 10.1139/w2012-040] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We have shown in previous research that the loss of phosphatidylglycerol and cardiolipin caused by disruption of the PGS1 gene is lethal for the petite-negative yeast Kluyveromyces lactis . This present study demonstrates the role and mechanism of atp2.1 in the suppression of pgs1 lethality in K. lactis cells. Phenotypic characterization has shown that a strain lacking the phosphatidylglycerolphosphate synthase (atp2.1pgs1Δ) possessed a markedly impaired respiratory chain, very low endogenous respiration, and uncoupled mitochondria. As a result the mutant strain was unable to generate a sufficient mitochondrial membrane potential via respiration. The atp2.1 suppressor mutation enabled an increase in the affinity of F(1)-ATPase for ATP in the hydrolytic reaction, resulting in the maintenance of sufficient membrane potential for the biogenesis of mitochondria and survival of cells lacking anionic phospholipid biosynthesis.
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Affiliation(s)
- Viktoria Palovicova
- Department of Microbiology and Virology, Faculty of Natural Sciences, Comenius University, Mlynská dolina B-2, Bratislava 842 15, Slovak Republic
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11
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Trono D, Soccio M, Laus MN, Pastore D. Potassium channel-oxidative phosphorylation relationship in durum wheat mitochondria from control and hyperosmotic-stressed seedlings. PLANT, CELL & ENVIRONMENT 2011; 34:2093-108. [PMID: 21819416 DOI: 10.1111/j.1365-3040.2011.02407.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Durum wheat mitochondria (DWM) possess an ATP-inhibited K(+) channel, the plant mitoK(ATP) (PmitoK(ATP) ), which is activated under environmental stress to control mitochondrial ROS production. To do this, PmitoK(ATP) collapses membrane potential (ΔΨ), thus suggesting mitochondrial uncoupling. We tested this point by studying oxidative phosphorylation (OXPHOS) in DWM purified from control seedlings and from seedlings subjected both to severe mannitol and NaCl stress. In severely-stressed DWM, the ATP synthesis via OXPHOS, continuously monitored by a spectrophotometric assay, was about 90% inhibited when the PmitoK(ATP) was activated by KCl. Contrarily, in control DWM, although PmitoK(ATP) collapsed ΔΨ, ATP synthesis, as well as coupling [respiratory control (RC) ratio and ratio between phosphorylated ADP and reduced oxygen (ADP/O)] checked by oxygen uptake experiments, were unaffected. We suggest that PmitoK(ATP) may play an important defensive role at the onset of the environmental/oxidative stress by preserving energy in a crucial moment for cell and mitochondrial bioenergetics. Consistently, under moderate mannitol stress, miming an early stress condition, the channel may efficiently control reactive oxygen species (ROS) generation (about 35-fold from fully open to closed state) without impairing ATP synthesis. Anyway, if the stress significantly proceeds, the PmitoK(ATP) becomes fully activated by decrease of ATP concentration (25-40%) and increase of activators [free fatty acids (FFAs) and superoxide anion], thus impairing ATP synthesis.
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Affiliation(s)
- Daniela Trono
- CRA - Centro di Ricerca per la Cerealicoltura, S.S. 16 Km 675, Dipartimento di Scienze Agroambientali, Chimica e Difesa Vegetale, Università di Foggia, Via Napoli 25, Italy
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12
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Mitochondrial Unselective Channels throughout the eukaryotic domain. Mitochondrion 2011; 11:382-90. [DOI: 10.1016/j.mito.2011.02.004] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Revised: 02/16/2011] [Accepted: 02/25/2011] [Indexed: 02/03/2023]
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13
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Cabrera-Orefice A, Guerrero-Castillo S, Luévano-Martínez LA, Peña A, Uribe-Carvajal S. Mitochondria from the salt-tolerant yeast Debaryomyces hansenii (halophilic organelles?). J Bioenerg Biomembr 2010; 42:11-9. [PMID: 20091106 DOI: 10.1007/s10863-009-9264-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2009] [Accepted: 12/04/2009] [Indexed: 11/28/2022]
Abstract
The yeast Debaryomyces hansenii is considered a marine organism. Sea water contains 0.6 M Na(+) and 10 mM K(+); these cations permeate into the cytoplasm of D. hansenii where proteins and organelles have to adapt to high salt concentrations. The effect of high concentrations of monovalent and divalent cations on isolated mitochondria from D. hansenii was explored. As in S. cerevisiae, these mitochondria underwent a phosphate-sensitive permeability transition (PT) which was inhibited by Ca(2+) or Mg(2+). However, D. hansenii mitochondria require higher phosphate concentrations to inhibit PT. In regard to K(+) and Na(+), and at variance with mitochondria from all other sources known, these monovalent cations promoted closure of the putative mitochondrial unspecific channel. This was evidenced by the K(+)/Na(+)-promoted increase in: respiratory control, transmembrane potential and synthesis of ATP. PT was equally sensitive to either Na(+) or K(+). In the presence of propyl-gallate PT was still observed while in the presence of cyanide the alternative pathway was not active enough to generate a Delta Psi due to a low AOX activity. In D. hansenii mitochondria K(+) and Na(+) optimize oxidative phosphorylation, providing an explanation for the higher growth efficiency in saline environments exhibited by this yeast.
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Affiliation(s)
- Alfredo Cabrera-Orefice
- Department of Biochemistry, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, México
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Gutiérrez-Aguilar M, Pérez-Martínez X, Chávez E, Uribe-Carvajal S. In Saccharomyces cerevisiae, the phosphate carrier is a component of the mitochondrial unselective channel. Arch Biochem Biophys 2009; 494:184-91. [PMID: 19995548 DOI: 10.1016/j.abb.2009.12.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2009] [Revised: 11/26/2009] [Accepted: 12/01/2009] [Indexed: 11/24/2022]
Abstract
The mitochondrial permeability transition (PT) involves the opening of a mitochondrial unselective channel (MUC) resulting in membrane depolarization and increased permeability to ions. PT has been observed in many, but not all eukaryotic species. In some species, PT has been linked to cell death, although other functions, such as matrix ion detoxification or regulation of the rate of oxygen consumption have been considered. The identification of the proteins constituting MUC would help understand the biochemistry and physiology of this channel. It has been suggested that the mitochondrial phosphate carrier is a structural component of MUC and we decided to test this in yeast mitochondria. Mersalyl inhibits the phosphate carrier and it has been reported that it also triggers PT. Mersalyl induced opening of the decavanadate-sensitive Yeast Mitochondrial Unselective Channel (YMUC). In isolated yeast mitochondria from a phosphate carrier-null strain the sensitivity to both phosphate and mersalyl was lost, although the permeability transition was still evoked by ATP in a decavanadate-sensitive fashion. Polyethylene glycol (PEG)-induced mitochondrial contraction results indicated that in mitochondria lacking the phosphate carrier the YMUC is smaller: complete contraction for mitochondria from the wild type and the mutant strains was achieved with 1.45 and 1.1 kDa PEGs, respectively. Also, as expected for a smaller channel titration with 1.1 kDa PEG evidenced a higher sensitivity in mitochondria from the mutant strain. The above data suggest that the phosphate carrier is the phosphate sensor in YMUC and contributes to the structure of this channel.
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Traba J, Froschauer EM, Wiesenberger G, Satrústegui J, Del Arco A. Yeast mitochondria import ATP through the calcium-dependent ATP-Mg/Pi carrier Sal1p, and are ATP consumers during aerobic growth in glucose. Mol Microbiol 2008; 69:570-85. [PMID: 18485069 DOI: 10.1111/j.1365-2958.2008.06300.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Sal1p, a novel Ca2+-dependent ATP-Mg/Pi carrier, is essential in yeast lacking all adenine nucleotide translocases. By targeting luciferase to the mitochondrial matrix to monitor mitochondrial ATP levels, we show in isolated mitochondria that both ATP-Mg and free ADP are taken up by Sal1p with a K(m) of 0.20 +/- 0.03 mM and 0.28 +/- 0.06 mM respectively. Nucleotide transport along Sal1p is strictly Ca2+ dependent. Ca2+ increases the V(max) with a S(0.5) of 15 muM, and no changes in the K(m) for ATP-Mg. Glucose sensing in yeast generates Ca2+ transients involving Ca2+ influx from the external medium. We find that carbon-deprived cells respond to glucose with an immediate increase in mitochondrial ATP levels which is not observed in the presence of EGTA or in Sal1p-deficient cells. Moreover, we now report that during normal aerobic growth on glucose, yeast mitochondria import ATP from the cytosol and hydrolyse it through H+-ATP synthase. We identify two pathways for ATP uptake in mitochondria, the ADP/ATP carriers and Sal1p. Thus, during exponential growth on glucose, mitochondria are ATP consumers, as those from cells growing in anaerobic conditions or deprived of mitochondrial DNA which depend on cytosolic ATP and mitochondrial ATPase working in reverse to generate a mitochondrial membrane potential. In conclusion, the results show that growth on glucose requires ATP hydrolysis in mitochondria and recruits Sal1p as a Ca2+-dependent mechanism to import ATP-Mg from the cytosol. Whether this mechanism is used under similar settings in higher eukaryotes is an open question.
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Affiliation(s)
- Javier Traba
- Departamento de Biologia Molecular, Centro de Biología Molecular Severo Ochoa UAM-CSIC, CIBER de Enfermedades Raras (CIBERER), Universidad Autónoma, Madrid, Spain
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16
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Pérez-Vázquez V, Saavedra-Molina A, Uribe S. In Saccharomyces cerevisiae, cations control the fate of the energy derived from oxidative metabolism through the opening and closing of the yeast mitochondrial unselective channel. J Bioenerg Biomembr 2004; 35:231-41. [PMID: 13678274 DOI: 10.1023/a:1024659615022] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The yeast mitochondrial unspecific channel (YMUC) sensitivity to inorganic (Ca2+ or Mg2+) or organic (hexyl or octyl-guanidine) cations was measured. The rate of oxygen consumption in State 3 and State 4, the transmembrane potential (deltapsi), mitochondrial swelling, and the polyethylene-glycol mediated recontraction were used to follow opening of the YMUC. Addition of 0.4 mM PO4 did not close the YMUC, although it did enhance the sensitivity to Ca2+ (I50 decreased from 50 to 0.3 mM) and Mg2+ (I50 decreased from 5 to 0.83 mM Mg2+). The Ca2+ concentration needed to close the YMUC was higher than the concentrations usually observed in the cell. Nonetheless, Mg2+, Ca2+, and PO4 exhibited additive effects. These cations did not inhibit contraction of preswollen mitochondria, suggesting that the YMUC/cation interaction was labile. Octyl-guanidine (OG-I50 7.5 microM) was the only cation which inhibited mitochondrial recontraction, probably as a result of membrane binding stabilization through its hydrophobic tail. The PO4-dependent, Ca(2+)/Mg(2+)-mediated closure of the YMUC may be a means to control the proportion of oxidative energy producing ATP or being lost as heat.
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Jung DW, Bradshaw PC, Litsky M, Pfeiffer DR. Ca2+ transport in mitochondria from yeast expressing recombinant aequorin. Anal Biochem 2004; 324:258-68. [PMID: 14690690 DOI: 10.1016/j.ab.2003.10.029] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
We have expressed aequorin in mitochondria of the yeast Saccharomyces cerevisiae and characterized the resulting strain with respect to mitochondrial Ca(2+) transport in vivo and in vitro. When intact cells are suspended in water containing 1.4 mM ethanol and 14 mM CaCl(2), the matrix free Ca(2+) concentration is 200 nM, similar to the values expected in cytoplasm. Addition of ionophore ETH 129 allows an active accumulation of Ca(2+) and promptly increases the value to 1.2 microM. Elevated Ca(2+) concentrations are maintained for periods of 6 min or longer under these conditions. Isolated yeast mitochondria oxidizing ethanol also accumulate Ca(2+) when ETH 129 is present, but the cation is not retained depending on the medium conditions. This finding confirms the presence of a Ca(2+) release mechanism that requires free fatty acids as previously described [P.C. Bradshaw et al. (2001) J. Biol. Chem. 276, 40502-40509]. When a respiratory substrate is not present, Ca(2+) enters and leaves yeast mitochondria slowly, at a specific activity near 0.2 nmol/min/mg protein. Transport under these conditions equilibrates the internal and external concentrations of Ca(2+) and is not affected by ruthenium red, uncouplers, or ionophores that perturb transmembrane gradients of charge and pH. This activity displays sigmoid kinetics and a K(1/2) value for Ca(2+) that is near to 900 nM, in the absence of ethanol or when it is present. It is furthermore shown that the activity coefficient of Ca(2+) in yeast mitochondria is a function of the matrix Ca(2+) content and is substantially larger than that in mammalian mitochondria. Characteristics of the aequorin-expressing strain appear suitable for its use in expression-based methods directed at cloning Ca(2+) transporters from mammalian mitochondria and for further examining the interrelationships between mitochondrial and cytoplasmic Ca(2+) in yeast.
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Affiliation(s)
- Dennis W Jung
- Department of Molecular and Cellular Biochemistry, The Ohio State University Medical Center, Columbus, OH 43210, USA
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Castrejón V, Peña A, Uribe S. Closure of the yeast mitochondria unspecific channel (YMUC) unmasks a Mg2+ and quinine sensitive K+ uptake pathway in Saccharomyces cerevisiae. J Bioenerg Biomembr 2002; 34:299-306. [PMID: 12392193 DOI: 10.1023/a:1020208619422] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The K+ uptake pathways in yeast mitochondria are still undefined. Nonetheless, the K+-mediated mitochondrial swelling observed in the absence of phosphate (PO4) and in the presence of a respiratory substrate has led to propose that large K+ movements occur in yeast mitochondria. Thus, the uptake of K+ by isolated yeast mitochondria was evaluated. Two parallel experiments were conducted to evaluate K+ transport; these were mitochondrial swelling and the uptake of the radioactive K+ analog 86Rb+. The opening of the yeast mitochondrial unspecific channel (YMUC) was regulated by different PO4 concentrations. The high protein concentrations used to measure 86Rb+ uptake resulted in a slight stabilization of the transmembrane potential at 0.4 mM PO4 but not at 0 or 4 mM PO4. At 4 mM PO4 swelling was inhibited while, in contrast, 86Rb+ uptake was still observed. The results suggest that an energy-dependent K+ uptake mechanism was unmasked when the YMUC was closed. To further analyze the properties of this K+ uptake system, the Mg2+ and quinine sensitivity of both swelling and 86Rb+ uptake were evaluated. Under the conditions where the unspecific pore was closed, K+ transport sensitivity to Mg2+ and quinine increased. In addition, when Zn2+ was added as an antiport inhibitor, uptake of 86Rb+ increased. It is suggested that in yeast mitochondria, the K+ concentration is highly regulated by the equilibrium of uptake and exit of this cation through two specific transporters.
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Affiliation(s)
- Vicente Castrejón
- Biochemistry Department, Instituto de Fisiología Celular, UNAM, Mexico City, Mexico
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Janssen MJFW, de Kruijff B, de Kroon AIPM. Phosphate is required to maintain the outer membrane integrity and membrane potential of respiring yeast mitochondria. Anal Biochem 2002; 300:27-33. [PMID: 11743688 DOI: 10.1006/abio.2001.5438] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The buffer requirements to maintain mitochondrial intactness and membrane potential in in vitro studies were investigated, using gradient purified yeast mitochondria. It was found that the presence of phosphate is crucial for generation of a stable membrane potential and for preserving the intactness of the outer membrane, as assessed by probing the accessibility of Tom40p to trypsin and the leakage of cytochrome b2 from the intermembrane space. Upon addition of respiratory substrate in the absence of phosphate, mitochondria generate a membrane potential that collapses within 1 min. Under the same conditions, the mitochondrial outer membrane is disrupted. The presence of phosphate prevents both phenomena. The DeltapH component of the proton motive force appears to be responsible for the compromised outer membrane integrity. The collapse of the membrane potential is reversible to a limited extent. Only when phosphate is added soon enough after the addition of exogenous respiratory substrate can a stable membrane potential be obtained again. Within a few minutes, this capacity is lost. The presence of Mg(2+) prevents rupture of the outer membrane, but does not prevent rapid dissipation of the membrane potential. Similar results were obtained for mitochondria isolated and stored in the presence of dextran or bovine serum albumin.
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Affiliation(s)
- Marjolein J F W Janssen
- Department of Biochemistry of Membranes, Centre for Biomembranes and Lipid Enzymology, Institute of Biomembranes, Utrecht University, Padualaan 8, Utrecht, NL-3584 CH, The Netherlands
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20
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Sánchez NS, Pearce DA, Cardillo TS, Uribe S, Sherman F. Requirements of Cyc2p and the porin, Por1p, for ionic stability and mitochondrial integrity in Saccharomyces cerevisiae. Arch Biochem Biophys 2001; 392:326-32. [PMID: 11488609 DOI: 10.1006/abbi.2001.2465] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It was previously demonstrated that Cyc2p from Saccharomyces cerevisiae is a mitochondrial protein; that the cyc2-Delta2 deletion lacking the entire gene causes a diminution to only approximately 20% of the normal levels of cytochrome c due to a partial deficiency in mitochondrial import of apo-cytochrome c; that the deletion causes a defective mitochondrial function, as revealed by diminished growth on media containing nonfermentable carbon sources; and that this defect is exacerbated in hyper-ionic KCl media and at higher incubation temperatures, but is suppressed on media containing sorbitol, a nonionic compound. We report that por1-Delta strains lacking the mitochondrial porin, Por1p, but not por2-Delta strains lacking the related porin, share some phenotypes similar to the cyc2-Delta2 strain, including hypersensitivity to KCl in glycerol medium. Moreover, spontaneous swelling in the presence of ATP was detected in mitochondria from the cyc2-Delta2 strain, while swelling could be detected in mitochondria from the other strains only after the addition of KCl. Thus, highly unspecific membrane permeation may be triggered by ATP in the cyc2-Delta2 strain. We suggest that Por1p and Cyc2p, in addition to their own unique functions, serve to maintain the osmotic stability of mitochondria, but by different mechanisms.
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Affiliation(s)
- N S Sánchez
- Department of Biochemistry, Universidad Nacional Autónoma de México, México, DF, 04510, México
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21
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Affiliation(s)
- M Schlame
- Department of Anesthesiology, Hospital for Special Surgery, Cornell University Medical College, 555 E. 70th St., New York, NY 10021, USA
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Koehler CM, Murphy MP, Bally NA, Leuenberger D, Oppliger W, Dolfini L, Junne T, Schatz G, Or E. Tim18p, a new subunit of the TIM22 complex that mediates insertion of imported proteins into the yeast mitochondrial inner membrane. Mol Cell Biol 2000; 20:1187-93. [PMID: 10648604 PMCID: PMC85242 DOI: 10.1128/mcb.20.4.1187-1193.2000] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
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.
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Affiliation(s)
- C M Koehler
- Biozentrum, University of Basel, CH-4056 Basel, Switzerland
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Cortés P, Castrejón V, Sampedro JG, Uribe S. Interactions of arsenate, sulfate and phosphate with yeast mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1456:67-76. [PMID: 10627296 DOI: 10.1016/s0005-2728(99)00109-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In the presence of K(+), addition of ATP or ethanol to yeast mitochondria triggers the depletion of the transmembrane potential (DeltaPsi) and this is prevented by millimolar concentrations of phosphate (PO(4)). Different monovalent and polyvalent anions were tested for their protective effects on mitochondria from Saccharomyces cerevisiae. Only arsenate (AsO(4)) and sulfate (SO(4)) were as efficient as PO(4) to protect mitochondria against the K(+) mediated swelling, depletion of the DeltaPsi, and decrease in the ratio of uncoupled state to state 4 respiration rates. Protection by PO(4), SO(4) or AsO(4) was inhibited by mersalyl, suggesting that these anions interact with a site located in the matrix side. In addition, the effects of SO(4) and AsO(4) on the F(1)F(0)-ATPase were tested: both SO(4) and AsO(4) inhibited the synthesis of ATP following competitive kinetics against PO(4) and non-competitive kinetics against ADP. The mersalyl sensitive uptake of (32)PO(4) was not inhibited by SO(4) or AsO(4), suggesting that the synthesis of ATP was inhibited at the F(1)F(0)-ATPase. The hydrolysis of ATP was not inhibited, only a stimulation was observed when AsO(4) or sulfite (SO(3)) were added. It is suggested that the structure and charge similarities of PO(4), AsO(4) and SO(4) result in undiscriminated binding to at least two sites located in the mitochondrial matrix: at one site, occupation by any of these three anions results in protection against uncoupling by K(+); at the second site, in the F(1)F(0)-ATPase, AsO(4) and SO(4) compete for binding against PO(4) leading to inhibition of the synthesis of ATP.
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Affiliation(s)
- P Cortés
- Department of Biochemistry, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México (UNAM), Apdo Postal 70-242, 04510, Mexico City, Mexico
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