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Benz R. Historical Perspective of Pore-Forming Activity Studies of Voltage-Dependent Anion Channel (Eukaryotic or Mitochondrial Porin) Since Its Discovery in the 70th of the Last Century. Front Physiol 2021; 12:734226. [PMID: 35547863 PMCID: PMC9083909 DOI: 10.3389/fphys.2021.734226] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 09/24/2021] [Indexed: 01/07/2023] Open
Abstract
Eukaryotic porin, also known as Voltage-Dependent Anion Channel (VDAC), is the most frequent protein in the outer membrane of mitochondria that are responsible for cellular respiration. Mitochondria are most likely descendants of strictly aerobic Gram-negative bacteria from the α-proteobacterial lineage. In accordance with the presumed ancestor, mitochondria are surrounded by two membranes. The mitochondrial outer membrane contains besides the eukaryotic porins responsible for its major permeability properties a variety of other not fully identified channels. It encloses also the TOM apparatus together with the sorting mechanism SAM, responsible for the uptake and assembly of many mitochondrial proteins that are encoded in the nucleus and synthesized in the cytoplasm at free ribosomes. The recognition and the study of electrophysiological properties of eukaryotic porin or VDAC started in the late seventies of the last century by a study of Schein et al., who reconstituted the pore from crude extracts of Paramecium mitochondria into planar lipid bilayer membranes. Whereas the literature about structure and function of eukaryotic porins was comparatively rare during the first 10years after the first study, the number of publications started to explode with the first sequencing of human Porin 31HL and the recognition of the important function of eukaryotic porins in mitochondrial metabolism. Many genomes contain more than one gene coding for homologs of eukaryotic porins. More than 100 sequences of eukaryotic porins are known to date. Although the sequence identity between them is relatively low, the polypeptide length and in particular, the electrophysiological characteristics are highly preserved. This means that all eukaryotic porins studied to date are anion selective in the open state. They are voltage-dependent and switch into cation-selective substates at voltages in the physiological relevant range. A major breakthrough was also the elucidation of the 3D structure of the eukaryotic pore, which is formed by 19 β-strands similar to those of bacterial porin channels. The function of the presumed gate an α-helical stretch of 20 amino acids allowed further studies with respect to voltage dependence and function, but its exact role in channel gating is still not fully understood.
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2
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Ravi B, Kanwar P, Sanyal SK, Bheri M, Pandey GK. VDACs: An Outlook on Biochemical Regulation and Function in Animal and Plant Systems. Front Physiol 2021; 12:683920. [PMID: 34421635 PMCID: PMC8375762 DOI: 10.3389/fphys.2021.683920] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 06/30/2021] [Indexed: 12/12/2022] Open
Abstract
The voltage-dependent anion channels (VDACs) are the most abundant proteins present on the outer mitochondrial membrane. They serve a myriad of functions ranging from energy and metabolite exchange to highly debatable roles in apoptosis. Their role in molecular transport puts them on the center stage as communicators between cytoplasmic and mitochondrial signaling events. Beyond their general role as interchangeable pores, members of this family may exhibit specific functions. Even after nearly five decades of their discovery, their role in plant systems is still a new and rapidly emerging field. The information on biochemical regulation of VDACs is limited. Various interacting proteins and post-translational modifications (PTMs) modulate VDAC functions, amongst these, phosphorylation is quite noticeable. In this review, we have tried to give a glimpse of the recent advancements in the biochemical/interactional regulation of plant VDACs. We also cover a critical analysis on the importance of PTMs in the functional regulation of VDACs. Besides, the review also encompasses numerous studies which can identify VDACs as a connecting link between Ca2+ and reactive oxygen species signaling in special reference to the plant systems.
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Affiliation(s)
| | | | | | | | - Girdhar K. Pandey
- Department of Plant Molecular Biology, University of Delhi, New Delhi, India
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3
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De Pinto V. Renaissance of VDAC: New Insights on a Protein Family at the Interface between Mitochondria and Cytosol. Biomolecules 2021; 11:biom11010107. [PMID: 33467485 PMCID: PMC7831034 DOI: 10.3390/biom11010107] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 01/10/2021] [Accepted: 01/12/2021] [Indexed: 12/14/2022] Open
Abstract
It has become impossible to review all the existing literature on Voltage-Dependent Anion selective Channel (VDAC) in a single article. A real Renaissance of studies brings this protein to the center of decisive knowledge both for cell physiology and therapeutic application. This review, after highlighting the similarities between the cellular context and the study methods of the solute carriers present in the inner membrane and VDAC in the outer membrane of the mitochondria, will focus on the isoforms of VDAC and their biochemical characteristics. In particular, the possible reasons for their evolutionary onset will be discussed. The variations in their post-translational modifications and the differences between the regulatory regions of their genes, probably the key to understanding the current presence of these genes, will be described. Finally, the situation in the higher eukaryotes will be compared to that of yeast, a unicellular eukaryote, where there is only one active isoform and the role of VDAC in energy metabolism is better understood.
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Affiliation(s)
- Vito De Pinto
- Department of Biomedicine and Biotechnology Sciences, University of Catania, Via S. Sofia 64, 95123 Catania, Italy; ; Tel.: +39-095-73842444
- we.MitoBiotech.srl, c.so Italia 172, 95129 Catania, Italy
- National Institute of Biostructures and Biosystems, Section of Catania, 00136 Rome, Italy
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4
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Zhang D, Yip YM, Li L. In silico construction of HK2-VDAC1 complex and investigating the HK2 binding-induced molecular gating mechanism of VDAC1. Mitochondrion 2016; 30:222-8. [PMID: 27544294 DOI: 10.1016/j.mito.2016.08.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Revised: 06/30/2016] [Accepted: 08/16/2016] [Indexed: 12/19/2022]
Abstract
Hexokinase 2 (HK2) binds to Voltage-Dependent Anion Channel 1 (VDAC1) on mitochondrial outer membrane (MOM) to facilitate a preferential access of ATP to HK2 for glycolysis, in order to maintain a constant energy source for cell proliferation in cancer especially. While previous studies have discovered that the VDAC1 N-terminal helix is responsible for regulating molecules from within mitochondria to cytoplasm, the molecular mechanism of how HK2 is able to regulate the ATP access remains elusive. We hereby propose a model for the HK2-VDAC1 association. The model is then subjected to molecular dynamics (MD) simulations, where we probe the effect of HK2 binding on the mobility of the VDAC1 N-terminal helix. Results from the simulations show that HK2 binding restricts the movement of the VDAC1 N-terminal helix. As a result, VDAC1 is kept in the open state most of the time and probably allows a constant supply of ATP to HK2 for glycolysis.
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Affiliation(s)
- Dawei Zhang
- School of Physics and Engineering, Henan University of Science and Technology, Luoyang 471023, PR China.
| | - Yew Mun Yip
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
| | - Liben Li
- School of Physics and Engineering, Henan University of Science and Technology, Luoyang 471023, PR China
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5
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Krammer EM, Homblé F, Prévost M. Molecular origin of VDAC selectivity towards inorganic ions: a combined molecular and Brownian dynamics study. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:1284-92. [PMID: 23313453 DOI: 10.1016/j.bbamem.2012.12.018] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Revised: 12/14/2012] [Accepted: 12/31/2012] [Indexed: 11/15/2022]
Abstract
The voltage-dependent anion channel (VDAC) serves as the major pore for metabolites and electrolytes in the outer mitochondrial membrane. To refine our understanding of ion permeation through this channel we performed an extensive Brownian (BD) and molecular dynamics (MD) study on the mouse VDAC isoform 1 wild-type and mutants (K20E, D30K, K61E, E158K and K252E). The selectivity and the conductance of the wild-type and of the variant channels computed from the BD trajectories are in agreement with experimental data. The calculated selectivity is shown to be very sensitive to slight conformational changes which may have some bearing on the variability of the selectivity values measured on the VDAC open state. The MD and BD free energy profiles of the ion permeation suggest that the pore region comprising the N-terminal helix and the barrel band encircling it predominantly controls the ion transport across the channel. The overall 12μs BD and 0.9μs MD trajectories of the mouse VDAC isoform 1 wild-type and mutants feature no distinct pathways for ion diffusion and no long-lived ion-protein interactions. The dependence of ion distribution in the wild-type channel with the salt concentration can be explained by an ionic screening of the permanent charges of the protein arising from the pore. Altogether these results bolster the role of electrostatic features of the pore as the main determinant of VDAC selectivity towards inorganic anions.
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Affiliation(s)
- Eva-Maria Krammer
- Structure et Fonction des Membranes Biologiques, Centre de Biologie Structurale et de Bioinformatique, Université Libre de Bruxelles (ULB), Boulevard du Triomphe CP 206/2, B-1050 Brussels, Belgium
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6
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Krammer EM, Homblé F, Prévost M. Concentration dependent ion selectivity in VDAC: a molecular dynamics simulation study. PLoS One 2011; 6:e27994. [PMID: 22164223 PMCID: PMC3229507 DOI: 10.1371/journal.pone.0027994] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Accepted: 10/29/2011] [Indexed: 11/19/2022] Open
Abstract
The voltage-dependent anion channel (VDAC) forms the major pore in the outer mitochondrial membrane. Its high conducting open state features a moderate anion selectivity. There is some evidence indicating that the electrophysiological properties of VDAC vary with the salt concentration. Using a theoretical approach the molecular basis for this concentration dependence was investigated. Molecular dynamics simulations and continuum electrostatic calculations performed on the mouse VDAC1 isoform clearly demonstrate that the distribution of fixed charges in the channel creates an electric field, which determines the anion preference of VDAC at low salt concentration. Increasing the salt concentration in the bulk results in a higher concentration of ions in the VDAC wide pore. This event induces a large electrostatic screening of the charged residues promoting a less anion selective channel. Residues that are responsible for the electrostatic pattern of the channel were identified using the molecular dynamics trajectories. Some of these residues are found to be conserved suggesting that ion permeation between different VDAC species occurs through a common mechanism. This inference is buttressed by electrophysiological experiments performed on bean VDAC32 protein akin to mouse VDAC.
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Affiliation(s)
- Eva-Maria Krammer
- Structure et Fonction des Membranes Biologiques, Université Libre de Bruxelles, Brussels, Belgium
| | - Fabrice Homblé
- Structure et Fonction des Membranes Biologiques, Université Libre de Bruxelles, Brussels, Belgium
| | - Martine Prévost
- Structure et Fonction des Membranes Biologiques, Université Libre de Bruxelles, Brussels, Belgium
- * E-mail:
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7
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Summers WA, Court DA. Origami in outer membrane mimetics: correlating the first detailed images of refolded VDAC with over 20 years of biochemical data. Biochem Cell Biol 2010; 88:425-38. [DOI: 10.1139/o09-115] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mitochondrial porin forms an aqueous pore in the outer membrane, through which selective passage of small metabolites and ions occurs, thereby regulating both mitochondrial function and cellular respiration. Investigations of the structure and function of porin have been performed with whole mitochondria, membrane vesicles, artificial membranes, and in detergent solutions, resulting in numerous models of porin structure. The mechanisms by which this protein functions are undoubtedly linked to its structure, which remained elusive until 2008, with reports of 3 high-resolution structures of this voltage-dependent, anion-selective channel (VDAC). The barrel structure is relatively simple yet unique: it is arranged as 19 anti-parallel β-strands, with β-strands 1 and 19 aligned parallel to each other to close the barrel. The N-terminal helical component is located within the lumen of the channel, although its precise structure and location in the lumen varies. With the basic barrel structure in hand, the data obtained in attempts to model the structure and understand porin over the past 20 years can be re-evaluated. Herein, using the mammalian VDAC structures as templates, the amassed electrophysiological and biochemical information has been reassessed with respect to the functional mechanisms of VDAC activity, with a focus on voltage-dependent gating.
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Affiliation(s)
- William A.T. Summers
- Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Deborah A. Court
- Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
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8
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VDAC, a multi-functional mitochondrial protein regulating cell life and death. Mol Aspects Med 2010; 31:227-85. [PMID: 20346371 DOI: 10.1016/j.mam.2010.03.002] [Citation(s) in RCA: 530] [Impact Index Per Article: 37.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2010] [Accepted: 03/17/2010] [Indexed: 01/22/2023]
Abstract
Research over the past decade has extended the prevailing view of the mitochondrion to include functions well beyond the generation of cellular energy. It is now recognized that mitochondria play a crucial role in cell signaling events, inter-organellar communication, aging, cell proliferation, diseases and cell death. Thus, mitochondria play a central role in the regulation of apoptosis (programmed cell death) and serve as the venue for cellular decisions leading to cell life or death. One of the mitochondrial proteins controlling cell life and death is the voltage-dependent anion channel (VDAC), also known as mitochondrial porin. VDAC, located in the mitochondrial outer membrane, functions as gatekeeper for the entry and exit of mitochondrial metabolites, thereby controlling cross-talk between mitochondria and the rest of the cell. VDAC is also a key player in mitochondria-mediated apoptosis. Thus, in addition to regulating the metabolic and energetic functions of mitochondria, VDAC appears to be a convergence point for a variety of cell survival and cell death signals mediated by its association with various ligands and proteins. In this article, we review what is known about the VDAC channel in terms of its structure, relevance to ATP rationing, Ca(2+) homeostasis, protection against oxidative stress, regulation of apoptosis, involvement in several diseases and its role in the action of different drugs. In light of our recent findings and the recently solved NMR- and crystallography-based 3D structures of VDAC1, the focus of this review will be on the central role of VDAC in cell life and death, addressing VDAC function in the regulation of mitochondria-mediated apoptosis with an emphasis on structure-function relations. Understanding structure-function relationships of VDAC is critical for deciphering how this channel can perform such a variety of functions, all important for cell life and death. This review also provides insight into the potential of VDAC1 as a rational target for new therapeutics.
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9
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Abstract
BACKGROUND Mitochondrial porins, or voltage-dependent anion-selective channels (VDAC) allow the passage of small molecules across the mitochondrial outer membrane, and are involved in complex interactions regulating organellar and cellular metabolism. Numerous organisms possess multiple porin isoforms, and initial studies indicated an intriguing evolutionary history for these proteins and the genes that encode them. RESULTS In this work, the wealth of recent sequence information was used to perform a comprehensive analysis of the evolutionary history of mitochondrial porins. Fungal porin sequences were well represented, and newly-released sequences from stramenopiles, alveolates, and seed and flowering plants were analyzed. A combination of Neighbour-Joining and Bayesian methods was used to determine phylogenetic relationships among the proteins. The aligned sequences were also used to reassess the validity of previously described eukaryotic porin motifs and to search for signature sequences characteristic of VDACs from plants, animals and fungi. Secondary structure predictions were performed on the aligned VDAC primary sequences and were used to evaluate the sites of intron insertion in a representative set of the corresponding VDAC genes. CONCLUSION Our phylogenetic analysis clearly shows that paralogs have appeared several times during the evolution of VDACs from the plants, metazoans, and even the fungi, suggesting that there are no "ancient" paralogs within the gene family. Sequence motifs characteristic of the members of the crown groups of organisms were identified. Secondary structure predictions suggest a common 16 beta-strand framework for the transmembrane arrangement of all porin isoforms. The GLK (and homologous or analogous motifs) and the eukaryotic porin motifs in the four representative Chordates tend to be in exons that appear to have changed little during the evolution of these metazoans. In fact there is phase correlation among the introns in these genes. Finally, our preliminary data support the notion that introns usually do not interrupt structural protein motifs, namely the predicted beta-strands. These observations concur with the concept of exon shuffling, wherein exons encode structural modules of proteins and the loss and gain of introns and the shuffling of exons via recombination events contribute to the complexity of modern day proteomes.
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10
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Graham BH, Craigen WJ. Genetic approaches to analyzing mitochondrial outer membrane permeability. Curr Top Dev Biol 2004; 59:87-118. [PMID: 14975248 DOI: 10.1016/s0070-2153(04)59004-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Affiliation(s)
- Brett H Graham
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
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11
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Bera AK, Ghosh S. Dual mode of gating of voltage-dependent anion channel as revealed by phosphorylation. J Struct Biol 2001; 135:67-72. [PMID: 11562167 DOI: 10.1006/jsbi.2001.4399] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The single-channel electrophysiological properties of the voltage-dependent anion channel (VDAC) of mitochondria from rat liver have been investigated under normal and phosphorylated (with protein kinase A) conditions. Experimental observations show that phosphorylation does not affect the current level and the opening probability in the positive clamping potentials, but leads to lowering of current magnitude and opening probability in the negative clamping potentials. The opening probability versus voltage (V) plot for native VDAC fits a Gaussian function symmetric around V = 0, whereas the same for phosphorylated VDAC fits a linear combination of two Gaussian functions. This indicates that there are two gating modes of VDAC; the negative voltage sensor (gate) undergoes modification due to phosphorylation.
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Affiliation(s)
- A K Bera
- Department of Biophysics, University of Delhi South Campus, Benito Juarez Road, New Delhi, 110021, India
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12
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Wu-Pong S. Alternative interpretations of the oligonucleotide transport literature: insights from nature. Adv Drug Deliv Rev 2000; 44:59-70. [PMID: 11035198 DOI: 10.1016/s0169-409x(00)00084-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Elucidation of the mechanism of oligonucleotide (ON) cellular internalization has met an impasse at the lipid penetration stage. ON internalization is commonly regarded to involve endocytosis, yet the method by which the ON penetrates the endosome membrane remains a mystery despite more than 10 years of research by multiple laboratories. In addition, the literature regarding this topic is fraught with discrepancies and inconsistencies. Therefore, the goal of this review is to propose and illustrate the feasibility of the notion that the literature discrepancies are perhaps an indication of a complex transport mechanism involving more than one uptake pathway. Accordingly, ON- and cell-differences in uptake may be attributed to differences in the relative importance of these pathways for different cell types and ONs. An example of one such pathway is reviewed and critiqued in this communication with respect to its hypothetical role in ON uptake. Other innovative mechanisms should similarly be considered to stimulate new ideas, discussion and research in this unique and interesting field.
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Affiliation(s)
- S Wu-Pong
- Department of Pharmaceutics, Box 980533, Virginia Commonwealth University, Richmond, VA 23298, USA.
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13
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Wiesner P, Popp B, Schmid A, Benz R, Kayser H. Isolation of mitochondrial porin of the fly Protophormia: porin modification by the pesticide CGA 140'408 studied in lipid bilayer membranes. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1282:216-24. [PMID: 8703976 DOI: 10.1016/0005-2736(96)00059-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Mitochondrial porin from the fly Protophormia was solubilized with detergent from whole mitochondria and purified by chromatography across a hydroxyapatite (HPT) column. The purified protein had an apparent molecular mass of about 30 kDa on SDS-PAGE. Partial sequencing of the protein confirmed that it is porin. When reconstituted in planar lipid bilayer membranes, porin formed ion-permeable channels with single-channel conductances of 2.4 and 4.5 nS in 1 M KCl. At low voltage, Protophormia porin displayed the properties of a general diffusion pore and had a small selectivity for anions over cations. At transmembrane potentials starting with about 20-30 mV, the channel switched in closed state, which is still ion-permeable. Our results suggest that Protophormia porin possesses functional properties similar to those of other mitochondrial porins. Porin was also isolated and purified from mitochondria, which were treated with the carbodiimide CGA 140'408 It represents the active derivative of diafenthiuron a new acaricide and insecticide. This carbodiimide labels both a F0-component of the inner membrane ATPase and outer membrane porin in a similar way as N,N'-dicyclohexylcarbodiimide (DCCD). Reconstitution experiments with the CGA 140'408-modified porin showed no significant effect of the modification on the single-channel conductance, suggesting that CGA 140'408 binds outside the channel. The voltage-dependence of the CGA 140'408-modified porin was changed with respect to the unmodified form. The closed configuration of the pesticide-modified channel was reached at smaller transmembrane potentials, suggesting a shift of the open to the closed state of Protophormia porin by pesticide binding. A possible contribution of this effect to the pesticide action is discussed.
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Affiliation(s)
- P Wiesner
- Lehrstuhl für Biotechnologie, Theodor-Boveri-Institut (Biozentrum), Universität Würzburg, Germany
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14
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Rudel T, Schmid A, Benz R, Kolb HA, Lang F, Meyer TF. Modulation of Neisseria porin (PorB) by cytosolic ATP/GTP of target cells: parallels between pathogen accommodation and mitochondrial endosymbiosis. Cell 1996; 85:391-402. [PMID: 8616894 DOI: 10.1016/s0092-8674(00)81117-4] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
PorB of the pathogenic Neisseria species belongs to the large family of pore-forming proteins (porins) produced by gram-negative bacteria. PorB is exceptional in that it is capable of translocating vectorially into membranes of infected target cells and functions in the infection process. Here we report on an unexpected similarity between Neisserial PorB and mitochondrial porins. Both porin classes interact with purine nucleoside triphosphates, which down-regulate pore size and cause a shift in voltage dependence and ion selectivity. Patch-clamp analyses indicate that PorB channel activity is tightly regulated in intact epithelial cells. In light of recent findings on the pivotal role of PorB in virulence and the prevention of phagosome lysosome fusion, these data provide important mechanistic clues on the intracellular pathogen accommodation reminiscent of mitochondrial endosymbiosis.
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Affiliation(s)
- T Rudel
- Max-Planck-Institut für Biologie, Abteilung Infektionsbiologie, Tübingen, Federal Republic of Germany
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15
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Reumann S, Maier E, Benz R, Heldt HW. The membrane of leaf peroxisomes contains a porin-like channel. J Biol Chem 1995; 270:17559-65. [PMID: 7542242 DOI: 10.1074/jbc.270.29.17559] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Spinach leaf peroxisomes were purified by Percoll density gradient centrifugation. After several freeze-thaw cycles, the peroxisomal membranes were separated from the matrix enzymes by sucrose density gradient centrifugation. The purity of the peroxisomal membranes was checked by measuring the activities of marker enzymes and by using antibodies. Lipid bilayer membrane experiments with the purified peroxisomal membranes, solubilized with a detergent, demonstrated that the membranes contain a channel-forming component, which may represent the major permeability pathway of these membranes. Control experiments with membranes of other cell organelles showed that the peroxisomal channel was not caused by the contamination of the peroxisomes with mitochondria or chloroplasts. The peroxisomal channel had a comparatively small single channel conductance of 350 pS in 1 M KCl as compared with channels from other cell organelles. The channel is slightly anion selective, which is in accordance with its physiological function. The single channel conductance was found to be only moderately dependent on the salt concentration in the aqueous phase. This may be explained by the presence of positive point net charges in or near the channel or by the presence of a saturable binding site inside the channel. The possible role of the channel in peroxisomal metabolism is discussed.
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Affiliation(s)
- S Reumann
- Institut für Biochemie der Pflanze, Universität Göttingen, Federal Republic of Germany
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16
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Porins from plants. Molecular cloning and functional characterization of two new members of the porin family. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(18)47312-7] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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17
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Benz R. Permeation of hydrophilic solutes through mitochondrial outer membranes: review on mitochondrial porins. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1197:167-96. [PMID: 8031826 DOI: 10.1016/0304-4157(94)90004-3] [Citation(s) in RCA: 347] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- R Benz
- Lehrstuhl für Biotechnologie, Theodor-Boveri-Institut (Biozentrum) der Universität Würzburg, Germany
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18
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Sorgato MC, Moran O. Channels in mitochondrial membranes: knowns, unknowns, and prospects for the future. Crit Rev Biochem Mol Biol 1993; 28:127-71. [PMID: 7683593 DOI: 10.3109/10409239309086793] [Citation(s) in RCA: 106] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Rapid diffusion of hydrophilic molecules across the outer membrane of mitochondria has been related to the presence of a protein of 29 to 37 kDa, called voltage-dependent anion channel (VDAC), able to generate large aqueous pores when integrated in planar lipid bilayers. Functional properties of VDAC from different origins appear highly conserved in artificial membranes: at low transmembrane potentials, the channel is in a highly conducting state, but a raise of the potential (both positive and negative) reduces drastically the current and changes the ionic selectivity from slightly anionic to cationic. It has thus been suggested that VDAC is not a mere molecular sieve but that it may control mitochondrial physiology by restricting the access of metabolites of different valence in response to voltage and/or by interacting with a soluble protein of the intermembrane space. The latest application of the patch clamp and tip-dip techniques, however, has indicated both a different electric behavior of the outer membrane and that other proteins may play a role in the permeation of molecules. Biochemical studies, use of site-directed mutants, and electron microscopy of two-dimensional crystal arrays of VDAC have contributed to propose a monomeric beta barrel as the structural model of the channel. An important insight into the physiology of the inner membrane of mammalian mitochondria has come from the direct observation of the membrane with the patch clamp. A slightly anionic, voltage-dependent conductance of 107 pS and one of 9.7 pS, K(+)-selective and ATP-sensitive, are the best characterized at the single channel level. Under certain conditions, however, the inner membrane can also show unselective nS peak transitions, possibly arising from a cooperative assembly of multiple substrates.
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Affiliation(s)
- M C Sorgato
- Dipartimento di Chimica Biologica, Università di Padova, Italy
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19
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Schmid A, Krömer S, Heldt HW, Benz R. Identification of two general diffusion channels in the outer membrane of pea mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1112:174-80. [PMID: 1281000 DOI: 10.1016/0005-2736(92)90389-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Reconstitution experiments were performed on lipid bilayer membranes in the presence of detergent solubilized mitochondrial membranes of pea seedlings (Pisum sativum). The addition of the detergent-solubilized material to the membranes resulted in a strong increase of the membrane conductance. To identify the proteins responsible for membrane activity the detergent extracts were applied to a hydroxyapatite (HTP) column and the fractions were tested for channel formation. The eluate of the column contained a protein which migrated as a single band with an apparent molecular mass of 30 kDa on SDS-PAGE. This channel was identified as the porin of pea mitochondria since it formed voltage-dependent channels with single-channel conductances of 1.5 and 3.7 nS in 1 M KCl and an estimated effective diameter of about 1.7 nm. Further elution of the column with KCl containing solutions yielded fractions which resulted in the formation of transient channels in lipid bilayer membranes. These channels had a single-channel conductance of 2.2 nS in 1 M KCl and had also the characteristics of general diffusion pores with an estimated effective diameter of 1.2 nm. Zero-current membrane potential measurements suggested that pea porin was anion-selective in the open state. The selectivity of the second channel was investigated by the measurement of the reversal potential. It was also slightly anion-selective. Its possible role in the metabolism of mitochondria is discussed.
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Affiliation(s)
- A Schmid
- Lehrstuhl für Biotechnologie, Biozentrum, Universität Würzburg, Germany
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20
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Purification, functional characterization, and cDNA sequencing of mitochondrial porin from Dictyostelium discoideum. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)36799-7] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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21
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Wyss M, Smeitink J, Wevers RA, Wallimann T. Mitochondrial creatine kinase: a key enzyme of aerobic energy metabolism. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1102:119-66. [PMID: 1390823 DOI: 10.1016/0005-2728(92)90096-k] [Citation(s) in RCA: 278] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- M Wyss
- Institute for Cell Biology, ETH Hönggerberg, Zürich, Switzerland
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22
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23
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Anderson WH, Thompson EW, Zwizinski CW. A rapid method for the preparation of yeast for immunoelectron microscopy using Lowicryl HM-20. JOURNAL OF ELECTRON MICROSCOPY TECHNIQUE 1991; 18:172-5. [PMID: 1886000 DOI: 10.1002/jemt.1060180212] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We describe a fixation and embedding procedure for the yeast Saccharomyces cerevisiae using Lowicryl HM-20 which is rapid, gives excellent fixation, and avoids the low temperature handling normally associated with embedding in this resin. This procedure yields superior structural preservation when compared to the commonly used rapid embedding procedure which employs Lowicryl K4M. We demonstrate that sections prepared using our rapid procedure are suitable for use in immunogold labelling experiments.
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Affiliation(s)
- W H Anderson
- Hormel Institute, University of Minnesota, Austin 55912
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24
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Adams V, Griffin L, Towbin J, Gelb B, Worley K, McCabe ER. Porin interaction with hexokinase and glycerol kinase: metabolic microcompartmentation at the outer mitochondrial membrane. BIOCHEMICAL MEDICINE AND METABOLIC BIOLOGY 1991; 45:271-91. [PMID: 1710914 DOI: 10.1016/0885-4505(91)90032-g] [Citation(s) in RCA: 123] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Porin is the pore-forming protein involved in the movement of adenine nucleotides across the outer mitochondrial membrane (OMM). Hexokinase and glycerol kinase interact with porin on the outer surface of the OMM in a manner which provides these enzymes with preferred access to the ATP generated in the mitochondrion. We review recent evidence which permits refinement of our knowledge of these proteins and their interactions at the OMM. The involvement of this system in metabolic microcompartmentation is discussed, as well as possible pathological consequences of its disruption in malignancy and genetic deficiencies of hexokinase, glycerol kinase, and porin.
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Affiliation(s)
- V Adams
- Institute for Molecular Genetics, Baylor College of Medicine, Houston, Texas 77030
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25
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Blachly-Dyson E, Peng S, Colombini M, Forte M. Selectivity changes in site-directed mutants of the VDAC ion channel: structural implications. Science 1990; 247:1233-6. [PMID: 1690454 DOI: 10.1126/science.1690454] [Citation(s) in RCA: 242] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The gene encoding the yeast mitochondrial outer membrane channel VDAC was subjected to site-directed mutagenesis to change amino acids at 29 positions to residues differing in charge from the wild-type sequence. The mutant genes were then expressed in yeast, and the physiological consequences of single and multiple amino acid changes were assessed after isolation and insertion of mutant channels into phospholipid bilayers. Selectivity changes were observed at 14 sites distributed throughout the length of the molecule. These sites are likely to define the position of the protein walls lining the aqueous pore and hence, the transmembrane segments. These results have been used to develop a model of the open state of the channel in which each polypeptide contributes 12 beta strands and one alpha helix to form the aqueous transmembrane pathway.
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Affiliation(s)
- E Blachly-Dyson
- Vollum Institute for Advanced Biomedical Research, Oregon Health Sciences University, Portland 97201
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26
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Benz R, Kottke M, Brdiczka D. The cationically selective state of the mitochondrial outer membrane pore: a study with intact mitochondria and reconstituted mitochondrial porin. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1022:311-8. [PMID: 1690571 DOI: 10.1016/0005-2736(90)90279-w] [Citation(s) in RCA: 123] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The outer mitochondrial membrane pore at a voltage above 20 to 30 mV can adopt a state of low conductance which may restrict free permeability of mitochondrial substrates. In order to obtain insight into the physiological meaning of this property we took advantage of the fact that the low conductance pore state could be induced by a polyanion in lipid bilayer membranes as well as in intact mitochondria. Upon reconstitution in artificial bilayers the pore in this substate became exclusively cation selective when the polarity of the applied voltage was negative on the cis-side. This behaviour of the pore would explain why induction of the low conductance pore state in intact mitochondria led to a complete inhibition of mitochondrial intermembranous kinases, such as creatine kinase and adenylate kinase, but not of peripheral kinases, for example hexokinase, when utilizing external ATP. The possibility that the inner membrane potential might be transduced to the outer membrane in the contact sites, suggests the existence of cation selective pores in these sites. This aspect may be important in the regulation of peripheral kinases like creatine kinase, nucleoside diphosphate kinase and adenylate kinase which are located behind the outer mitochondrial membrane.
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Affiliation(s)
- R Benz
- Fakultät für Biologie, Universität Konstanz, F.R.G
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27
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Benz R. Biophysical properties of porin pores from mitochondrial outer membrane of eukaryotic cells. EXPERIENTIA 1990; 46:131-7. [PMID: 1689250 DOI: 10.1007/bf02027308] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The matrix space of mitochondria is surrounded by two membranes. The mitochondrial inner membrane contains the respiration chain and a large number of highly specific carriers for the mostly anionic substrates of mitochondrial metabolism. In contrast to this the permeability properties of the mitochondrial outer membrane are by far less specific. It acts as a molecular sieve for hydrophilic molecules with a defined exclusion limit around 3000 Da. Responsible for the extremely high permeability of the mitochondrial outer membrane is the presence of a pore-forming protein termed mitochondrial porin. Mitochondrial porins have been isolated from a variety of eukaryotic cells. They are basic proteins with molecular masses between 30 and 35 kDa. Reconstitution experiments define their function as pore-forming components with a single-channel conductance of about 0.40 nS (nano Siemens) in 0.1 M KCl at low voltages. In the open state mitochondrial porin behaves as a general diffusion pore with an effective diameter of 1.7 nm. Eukaryotic porins are slightly anion-selective in the open state but become cation-selective after voltage-dependent closure.
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Affiliation(s)
- R Benz
- Lehrstuhl für Biotechnologie, Universität Würzburg, Federal Republic of Germany
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28
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Affiliation(s)
- M Colombini
- Department of Zoology, University of Maryland, College Park 20742
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Benz R, Schmid A, Dihanich M. Pores from mitochondrial outer membranes of yeast and a porin-deficient yeast mutant: a comparison. J Bioenerg Biomembr 1989; 21:439-50. [PMID: 2478530 DOI: 10.1007/bf00762516] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Reconstitution experiments were performed on lipid bilayer membranes in the presence of purified mitochondrial porin from yeast and of detergent-solubilized mitochondrial outer membranes of a porin-free yeast mutant. The addition of the porin resulted in a strong increase of the membrane conductance, which was caused by the formation of ion-permeable channels in the membranes. Yeast porin has a single-channel conductance of 4.2 nS in 1 M KCl. In the open state it behaves as a general diffusion pore with an effective diameter of 1.7 nm and possesses properties similar to other mitochondrial porins. Surprisingly, the membrane conductance also increased in the presence of detergent extracts of the mitochondrial outer membrane of the mutant. Single-channel recordings of lipid bilayer membranes in the presence of small concentration of the mutant membranes suggested that this membrane also contained a pore. The reconstituted pores had a single-channel conductance of 2.0 nS in 1 M KCl and the characteristics of general diffusion pores with an estimated effective diameter of 1.2 nm. This means that the pores present in the mitochondrial outer membranes of the yeast mutant have a much smaller effective diameter than "normal" mitochondrial porins. Zero-current membrane potential measurements suggested that the second mitochondrial porin is slightly cation-selective, while yeast porin is slightly anion-selective in the open state but highly cation-selective in the closed state. The possible role of these pores in the metabolism of mitochondria is discussed.
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Affiliation(s)
- R Benz
- Lehrstuhl für Biotechnologie, Universität Würzburg, F.R.G
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30
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Dihanich M, Schmid A, Oppliger W, Benz R. Identification of a new pore in the mitochondrial outer membrane of a porin-deficient yeast mutant. EUROPEAN JOURNAL OF BIOCHEMISTRY 1989; 181:703-8. [PMID: 2471638 DOI: 10.1111/j.1432-1033.1989.tb14780.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Reconstitution experiments were performed on lipid bilayer membranes in the presence of detergent-solubilized mitochondrial outer membranes of a porin-free yeast mutant and of its parent strain. The addition of the detergent-solubilized material resulted in a strong increase in the membrane conductance which was not observed if only the detergent was added to the aqueous phase. Surprisingly, the membrane conductance induced by the detergent extracts of the mutant membrane was only a factor of 20 less than that caused by the outer membrane of the parent strain under otherwise identical conditions. Single-channel recordings of lipid bilayer membranes in the presence of mitochondrial outer membranes of the yeast mutant suggested the presence of a transient pore. The reconstituted pores had a single-channel conductance of 0.21 nS in 0.1 M KCl and the characteristics of general diffusion pores with an estimated effective diameter of 1.2 nm. The pores present in the mitochondrial outer membranes of the yeast mutant shared some similarities with the pores formed by mitochondrial and bacterial porins although their effective diameter is much smaller than those of the 'normal' mitochondrial porins which have a single-channel conductance of about 0.4 nS in 0.1 M KCl, corresponding to an effective diameter of 1.7 nm. Zero-current membrane-potential measurements suggested that the second mitochondrial porin is slightly cation-selective. Its possible role in the metabolism of mitochondria is discussed.
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Ludwig O, Benz R, Schultz JE. Porin of Paramecium mitochondria isolation, characterization and ion selectivity of the closed state. BIOCHIMICA ET BIOPHYSICA ACTA 1989; 978:319-27. [PMID: 2536559 DOI: 10.1016/0005-2736(89)90131-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Porin was isolated and purified from mitochondria of Paramecium tetraurelia. The protein showed a single band of apparent Mr 37,000 on sodium dodecyl sulfate polyacrylamide electrophoretograms. The reconstitution of the protein into artificial lipid bilayer membranes revealed it to be a porin giving pores with an average single-channel conductance of 0.26 nS in 0.1 M KCl. This conductance is about half of that of other eukaryotic porins studied to date. The pore formed by the mitochondrial porin of Paramecium was found to be voltage-dependent and switched to a defined substrate at membrane voltages larger than 20 mV. In the open state the pore exhibited the characteristics of a general diffusion pore because the mobility sequence of the ions inside the pore was similar to that in the bulk aqueous phase. The effective diameter was estimated to be about 1.3 nm. The properties of the low conductance state of the pore were studied in detail. In this state the pore favored the passage of cations, in contrast to the open state which favored anions slightly. The possible role of the low-conductance state in the regulation of transport processes across the outer mitochondrial membrane and in mitochondrial metabolism is discussed.
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Affiliation(s)
- O Ludwig
- Lehrstuhl für Biotechnologie, Universität Würzburg, F.R.G
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32
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Benz R, Bauer K. Permeation of hydrophilic molecules through the outer membrane of gram-negative bacteria. Review on bacterial porins. EUROPEAN JOURNAL OF BIOCHEMISTRY 1988; 176:1-19. [PMID: 2901351 DOI: 10.1111/j.1432-1033.1988.tb14245.x] [Citation(s) in RCA: 235] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- R Benz
- Lehrstuhl für Biotechnologie, Universität Würzburg, Federal Republic of Germany
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