1
|
Dong F, Lojko P, Bazzone A, Bernhard F, Borodina I. Transporter function characterization via continuous-exchange cell-free synthesis and solid supported membrane-based electrophysiology. Bioelectrochemistry 2024; 159:108732. [PMID: 38810322 DOI: 10.1016/j.bioelechem.2024.108732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Revised: 05/02/2024] [Accepted: 05/13/2024] [Indexed: 05/31/2024]
Abstract
Functional characterization of transporters is impeded by the high cost and technical challenges of current transporter assays. Thus, in this work, we developed a new characterization workflow that combines cell-free protein synthesis (CFPS) and solid supported membrane-based electrophysiology (SSME). For this, membrane protein synthesis was accomplished in a continuous exchange cell-free system (CECF) in the presence of nanodiscs. The resulting transporters expressed in nanodiscs were incorporated into proteoliposomes and assayed in the presence of different substrates using the surface electrogenic event reader. As a proof of concept, we validated this workflow to express and characterize five diverse transporters: the drug/H+-coupled antiporters EmrE and SugE, the lactose permease LacY, the Na+/H+ antiporter NhaA from Escherichia coli, and the mitochondrial carrier AAC2 from Saccharomyces cerevisiae. For all transporters kinetic parameters, such as KM, IMAX, and pH dependency, were evaluated. This robust and expedite workflow (e.g., can be executed within only five workdays) offers a convenient direct functional assessment of transporter protein activity and has the ability to facilitate applications of transporters in medical and biotechnological research.
Collapse
Affiliation(s)
- Fang Dong
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Denmark
| | - Pawel Lojko
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Denmark
| | | | - Frank Bernhard
- Institute of Biophysical Chemistry, Centre for Biomolecular Magnetic Resonance, J.W. Goethe-University, Frankfurt am Main, Germany
| | - Irina Borodina
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Denmark.
| |
Collapse
|
2
|
Goyal S, Cambronne XA. Layered mechanisms regulating the human mitochondrial NAD+ transporter SLC25A51. Biochem Soc Trans 2023; 51:1989-2004. [PMID: 38108469 PMCID: PMC10802112 DOI: 10.1042/bst20220318] [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: 09/19/2023] [Revised: 11/28/2023] [Accepted: 12/08/2023] [Indexed: 12/19/2023]
Abstract
SLC25A51 is the primary mitochondrial NAD+ transporter in humans and controls many local reactions by mediating the influx of oxidized NAD+. Intriguingly, SLC25A51 lacks several key features compared with other members in the mitochondrial carrier family, thus its molecular mechanism has been unclear. A deeper understanding would shed light on the control of cellular respiration, the citric acid cycle, and free NAD+ concentrations in mammalian mitochondria. This review discusses recent insights into the transport mechanism of SLC25A51, and in the process highlights a multitiered regulation that governs NAD+ transport. The aspects regulating SLC25A51 import activity can be categorized as contributions from (1) structural characteristics of the transporter itself, (2) its microenvironment, and (3) distinctive properties of the transported ligand. These unique mechanisms further evoke compelling new ideas for modulating the activity of this transporter, as well as new mechanistic models for the mitochondrial carrier family.
Collapse
Affiliation(s)
- Shivansh Goyal
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712
| | - Xiaolu A. Cambronne
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712
| |
Collapse
|
3
|
Garcia GC, Gupta K, Bartol TM, Sejnowski TJ, Rangamani P. Mitochondrial morphology governs ATP production rate. J Gen Physiol 2023; 155:e202213263. [PMID: 37615622 PMCID: PMC10450615 DOI: 10.1085/jgp.202213263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 03/21/2023] [Accepted: 07/07/2023] [Indexed: 08/25/2023] Open
Abstract
Life is based on energy conversion. In particular, in the nervous system, significant amounts of energy are needed to maintain synaptic transmission and homeostasis. To a large extent, neurons depend on oxidative phosphorylation in mitochondria to meet their high energy demand. For a comprehensive understanding of the metabolic demands in neuronal signaling, accurate models of ATP production in mitochondria are required. Here, we present a thermodynamically consistent model of ATP production in mitochondria based on previous work. The significant improvement of the model is that the reaction rate constants are set such that detailed balance is satisfied. Moreover, using thermodynamic considerations, the dependence of the reaction rate constants on membrane potential, pH, and substrate concentrations are explicitly provided. These constraints assure that the model is physically plausible. Furthermore, we explore different parameter regimes to understand in which conditions ATP production or its export are the limiting steps in making ATP available in the cytosol. The outcomes reveal that, under the conditions used in our simulations, ATP production is the limiting step and not its export. Finally, we performed spatial simulations with nine 3-D realistic mitochondrial reconstructions and linked the ATP production rate in the cytosol with morphological features of the organelles.
Collapse
Affiliation(s)
- Guadalupe C. Garcia
- Computational Neurobiology Laboratory, Salk Institute for Biological Studies, La Jolla, CA, USA
| | - Kavya Gupta
- Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, CA, USA
| | - Thomas M. Bartol
- Computational Neurobiology Laboratory, Salk Institute for Biological Studies, La Jolla, CA, USA
| | - Terrence J. Sejnowski
- Computational Neurobiology Laboratory, Salk Institute for Biological Studies, La Jolla, CA, USA
| | - Padmini Rangamani
- Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, CA, USA
| |
Collapse
|
4
|
Mavridou V, King MS, Tavoulari S, Ruprecht JJ, Palmer SM, Kunji ERS. Substrate binding in the mitochondrial ADP/ATP carrier is a step-wise process guiding the structural changes in the transport cycle. Nat Commun 2022; 13:3585. [PMID: 35739110 PMCID: PMC9226169 DOI: 10.1038/s41467-022-31366-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Accepted: 06/14/2022] [Indexed: 02/02/2023] Open
Abstract
Mitochondrial ADP/ATP carriers import ADP into the mitochondrial matrix and export ATP to the cytosol to fuel cellular processes. Structures of the inhibited cytoplasmic- and matrix-open states have confirmed an alternating access transport mechanism, but the molecular details of substrate binding remain unresolved. Here, we evaluate the role of the solvent-exposed residues of the translocation pathway in the process of substrate binding. We identify the main binding site, comprising three positively charged and a set of aliphatic and aromatic residues, which bind ADP and ATP in both states. Additionally, there are two pairs of asparagine/arginine residues on opposite sides of this site that are involved in substrate binding in a state-dependent manner. Thus, the substrates are directed through a series of binding poses, inducing the conformational changes of the carrier that lead to their translocation. The properties of this site explain the electrogenic and reversible nature of adenine nucleotide transport.
Collapse
Affiliation(s)
- Vasiliki Mavridou
- grid.5335.00000000121885934Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge Biomedical Campus, Keith Peters Building, Hills Road, Cambridge, CB2 0XY UK
| | - Martin S. King
- grid.5335.00000000121885934Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge Biomedical Campus, Keith Peters Building, Hills Road, Cambridge, CB2 0XY UK
| | - Sotiria Tavoulari
- grid.5335.00000000121885934Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge Biomedical Campus, Keith Peters Building, Hills Road, Cambridge, CB2 0XY UK
| | - Jonathan J. Ruprecht
- grid.5335.00000000121885934Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge Biomedical Campus, Keith Peters Building, Hills Road, Cambridge, CB2 0XY UK
| | - Shane M. Palmer
- grid.5335.00000000121885934Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge Biomedical Campus, Keith Peters Building, Hills Road, Cambridge, CB2 0XY UK
| | - Edmund R. S. Kunji
- grid.5335.00000000121885934Medical Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge Biomedical Campus, Keith Peters Building, Hills Road, Cambridge, CB2 0XY UK
| |
Collapse
|
5
|
Molecular mechanism of thiamine pyrophosphate import into mitochondria: a molecular simulation study. J Comput Aided Mol Des 2021; 35:987-1007. [PMID: 34406552 DOI: 10.1007/s10822-021-00414-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Accepted: 07/26/2021] [Indexed: 10/20/2022]
Abstract
The import of thiamine pyrophosphate (TPP) through both mitochondrial membranes was studied using a total of 3-µs molecular dynamics simulations. Regarding the translocation through the mitochondrial outer membrane, our simulations support the conjecture that TPP uses the voltage-dependent anion channel, the major pore of this membrane, for its passage to the intermembrane space, as its transport presents significant analogies with that used by other metabolites previously studied, in particular with ATP. As far as passing through the mitochondrial inner membrane is concerned, our simulations show that the specific carrier of TPP has a single binding site that becomes accessible, through an alternating access mechanism. The preference of this transporter for TPP can be rationalized mainly by three residues located in the binding site that differ from those identified in the ATP/ADP carrier, the most studied member of the mitochondrial carrier family. The simulated transport mechanism of TPP highlights the essential role, at the energetic level, of the contributions coming from the formation and breakage of two networks of salt bridges, one on the side of the matrix and the other on the side of the intermembrane space, as well as the interactions, mainly of an ionic nature, formed by TPP upon its binding. The energy contribution provided by the cytosolic network establishes a lower barrier than that of the matrix network, which can be explained by the lower interaction energy of TPP on the matrix side or possibly a uniport activity.
Collapse
|
6
|
Sváb G, Kokas M, Sipos I, Ambrus A, Tretter L. Methylene Blue Bridges the Inhibition and Produces Unusual Respiratory Changes in Complex III-Inhibited Mitochondria. Studies on Rats, Mice and Guinea Pigs. Antioxidants (Basel) 2021; 10:antiox10020305. [PMID: 33669457 PMCID: PMC7920423 DOI: 10.3390/antiox10020305] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 02/04/2021] [Accepted: 02/10/2021] [Indexed: 11/23/2022] Open
Abstract
Methylene blue (MB) is used in human therapy in various pathological conditions. Its effects in neurodegenerative disease models are promising. MB acts on multiple cellular targets and mechanisms, but many of its potential beneficial effects are ascribed to be mitochondrial. According to the “alternative electron transport” hypothesis, MB is capable of donating electrons to cytochrome c bypassing complex I and III. As a consequence of this, the deleterious effects of the inhibitors of complex I and III can be ameliorated by MB. Recently, the beneficial effects of MB exerted on complex III-inhibited mitochondria were debated. In the present contribution, several pieces of evidence are provided towards that MB is able to reduce cytochrome c and improve bioenergetic parameters, like respiration and membrane potential, in mitochondria treated with complex III inhibitors, either antimycin or myxothiazol. These conclusions were drawn from measurements for mitochondrial oxygen consumption, membrane potential, NAD(P)H steady state, MB uptake and MB-cytochrome c oxidoreduction. In the presence of MB and complex III inhibitors, unusual respiratory reactions, like decreased oxygen consumption as a response to ADP addition as well as stimulation of respiration upon administration of inhibitors of ATP synthase or ANT, were observed. Qualitatively identical results were obtained in three rodent species. The actual metabolic status of mitochondria is well reflected in the distribution of MB amongst various compartments of this organelle.
Collapse
Affiliation(s)
- Gergely Sváb
- Laboratory of Neurobiochemistry, Department of Biochemistry, Institute of Biochemistry and Molecular Biology MTA-SE, Semmelweis University, POB. 262 Budapest, H-1444 Budapest, Hungary; (G.S.); (M.K.); (A.A.)
| | - Márton Kokas
- Laboratory of Neurobiochemistry, Department of Biochemistry, Institute of Biochemistry and Molecular Biology MTA-SE, Semmelweis University, POB. 262 Budapest, H-1444 Budapest, Hungary; (G.S.); (M.K.); (A.A.)
| | - Ildikó Sipos
- Department of Neurology, Semmelweis University, POB. 262 Budapest, H-1444 Budapest, Hungary;
| | - Attila Ambrus
- Laboratory of Neurobiochemistry, Department of Biochemistry, Institute of Biochemistry and Molecular Biology MTA-SE, Semmelweis University, POB. 262 Budapest, H-1444 Budapest, Hungary; (G.S.); (M.K.); (A.A.)
| | - László Tretter
- Laboratory of Neurobiochemistry, Department of Biochemistry, Institute of Biochemistry and Molecular Biology MTA-SE, Semmelweis University, POB. 262 Budapest, H-1444 Budapest, Hungary; (G.S.); (M.K.); (A.A.)
- Correspondence: ; Tel.: +36-1-459-1500/60010
| |
Collapse
|
7
|
Abstract
Members of the mitochondrial carrier family [solute carrier family 25 (SLC25)] transport nucleotides, amino acids, carboxylic acids, fatty acids, inorganic ions, and vitamins across the mitochondrial inner membrane. They are important for many cellular processes, such as oxidative phosphorylation of lipids and sugars, amino acid metabolism, macromolecular synthesis, ion homeostasis, cellular regulation, and differentiation. Here, we describe the functional elements of the transport mechanism of mitochondrial carriers, consisting of one central substrate-binding site and two gates with salt-bridge networks on either side of the carrier. Binding of the substrate during import causes three gate elements to rotate inward, forming the cytoplasmic network and closing access to the substrate-binding site from the intermembrane space. Simultaneously, three core elements rock outward, disrupting the matrix network and opening the substrate-binding site to the matrix side of the membrane. During export, substrate binding triggers conformational changes involving the same elements but operating in reverse.
Collapse
Affiliation(s)
- J J Ruprecht
- Medical Research Council Mitochondrial Biology Unit, Keith Peters Building, University of Cambridge, Cambridge CB2 0XY, United Kingdom; ,
| | - E R S Kunji
- Medical Research Council Mitochondrial Biology Unit, Keith Peters Building, University of Cambridge, Cambridge CB2 0XY, United Kingdom; ,
| |
Collapse
|
8
|
Bottani E, Lamperti C, Prigione A, Tiranti V, Persico N, Brunetti D. Therapeutic Approaches to Treat Mitochondrial Diseases: "One-Size-Fits-All" and "Precision Medicine" Strategies. Pharmaceutics 2020; 12:E1083. [PMID: 33187380 PMCID: PMC7696526 DOI: 10.3390/pharmaceutics12111083] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 11/08/2020] [Accepted: 11/09/2020] [Indexed: 12/11/2022] Open
Abstract
Primary mitochondrial diseases (PMD) refer to a group of severe, often inherited genetic conditions due to mutations in the mitochondrial genome or in the nuclear genes encoding for proteins involved in oxidative phosphorylation (OXPHOS). The mutations hamper the last step of aerobic metabolism, affecting the primary source of cellular ATP synthesis. Mitochondrial diseases are characterized by extremely heterogeneous symptoms, ranging from organ-specific to multisystemic dysfunction with different clinical courses. The limited information of the natural history, the limitations of currently available preclinical models, coupled with the large variability of phenotypical presentations of PMD patients, have strongly penalized the development of effective therapies. However, new therapeutic strategies have been emerging, often with promising preclinical and clinical results. Here we review the state of the art on experimental treatments for mitochondrial diseases, presenting "one-size-fits-all" approaches and precision medicine strategies. Finally, we propose novel perspective therapeutic plans, either based on preclinical studies or currently used for other genetic or metabolic diseases that could be transferred to PMD.
Collapse
Affiliation(s)
- Emanuela Bottani
- Department of Diagnostics and Public Health, Section of Pharmacology, University of Verona, 37134 Verona, Italy
| | - Costanza Lamperti
- Medical Genetics and Neurogenetics Unit, Fondazione IRCCS Istituto Neurologico C. Besta, 20126 Milan, Italy; (C.L.); (V.T.)
| | - Alessandro Prigione
- Department of General Pediatrics, Neonatology, and Pediatric Cardiology, University Clinic Düsseldorf (UKD), Heinrich Heine University (HHU), 40225 Dusseldorf, Germany;
| | - Valeria Tiranti
- Medical Genetics and Neurogenetics Unit, Fondazione IRCCS Istituto Neurologico C. Besta, 20126 Milan, Italy; (C.L.); (V.T.)
| | - Nicola Persico
- Department of Clinical Science and Community Health, University of Milan, 20122 Milan, Italy;
- Fetal Medicine and Surgery Service, Fondazione IRCCS Ca’ Granda, Ospedale Maggiore Policlinico, 20122 Milan, Italy
| | - Dario Brunetti
- Medical Genetics and Neurogenetics Unit, Fondazione IRCCS Istituto Neurologico C. Besta, 20126 Milan, Italy; (C.L.); (V.T.)
- Department of Medical Biotechnology and Translational Medicine, University of Milan, 20129 Milan, Italy
| |
Collapse
|
9
|
Abstract
Here, we present a protocol for the functional characterization of the H+-coupled human peptide transporter PepT1 and sufficient notes to transfer the protocol to the Na+-coupled sugar transporter SGLT1, the organic cation transporter OCT2, the Na+/Ca2+ exchanger NCX, and the neuronal glutamate transporter EAAT3.The assay was developed for the commercially available SURFE2R N1 instrument (Nanion Technologies GmbH) which applies solid supported membrane (SSM)-based electrophysiology. This technique is widely used for the functional characterization of membrane transporters with more than 100 different transporters characterized so far. The technique is cost-effective, easy to use, and capable of high-throughput measurements.SSM-based electrophysiology utilizes SSM-coated gold sensors to physically adsorb membrane vesicles containing the protein of interest. A fast solution exchange provides the substrate and activates transport. For the measurement of PepT1 activity, we applied a peptide concentration jump to activate H+/peptide symport. Proton influx charges the sensor. A capacitive current is measured reflecting the transport activity of PepT1 . Multiple measurements on the same sensor allow for comparison of transport activity under different conditions. Here, we determine EC50 for PepT1-mediated glycylglycine transport and perform an inhibition experiment using the specific peptide inhibitor Lys[Z(NO2)]-Val.
Collapse
|
10
|
Mitochondrial morphology provides a mechanism for energy buffering at synapses. Sci Rep 2019; 9:18306. [PMID: 31797946 PMCID: PMC6893035 DOI: 10.1038/s41598-019-54159-1] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Accepted: 10/24/2019] [Indexed: 01/27/2023] Open
Abstract
Mitochondria as the main energy suppliers of eukaryotic cells are highly dynamic organelles that fuse, divide and are transported along the cytoskeleton to ensure cellular energy homeostasis. While these processes are well established, substantial evidence indicates that the internal structure is also highly variable in dependence on metabolic conditions. However, a quantitative mechanistic understanding of how mitochondrial morphology affects energetic states is still elusive. To address this question, we here present an agent-based multiscale model that integrates three-dimensional morphologies from electron microscopy tomography with the molecular dynamics of the main ATP producing components. We apply our modeling approach to mitochondria at the synapse which is the largest energy consumer within the brain. Interestingly, comparing the spatiotemporal simulations with a corresponding space-independent approach, we find minor spatial effects when the system relaxes toward equilibrium but a qualitative difference in fluctuating environments. These results suggest that internal mitochondrial morphology is not only optimized for ATP production but also provides a mechanism for energy buffering and may represent a mechanism for cellular robustness.
Collapse
|
11
|
The SLC25 Mitochondrial Carrier Family: Structure and Mechanism. Trends Biochem Sci 2019; 45:244-258. [PMID: 31787485 PMCID: PMC7611774 DOI: 10.1016/j.tibs.2019.11.001] [Citation(s) in RCA: 189] [Impact Index Per Article: 37.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 10/30/2019] [Accepted: 11/01/2019] [Indexed: 12/27/2022]
Abstract
Members of the mitochondrial carrier family (SLC25) provide the transport steps for amino acids, carboxylic acids, fatty acids, cofactors, inorganic ions, and nucleotides across the mitochondrial inner membrane and are crucial for many cellular processes. Here, we use new insights into the transport mechanism of the mitochondrial ADP/ATP carrier to examine the structure and function of other mitochondrial carriers. They all have a single substrate-binding site and two gates, which are present on either side of the membrane and involve salt-bridge networks. Transport is likely to occur by a common mechanism, in which the coordinated movement of six structural elements leads to the alternating opening and closing of the matrix or cytoplasmic side of the carriers.
Collapse
|
12
|
Zorova LD, Popkov VA, Plotnikov EY, Silachev DN, Pevzner IB, Jankauskas SS, Babenko VA, Zorov SD, Balakireva AV, Juhaszova M, Sollott SJ, Zorov DB. Mitochondrial membrane potential. Anal Biochem 2018; 552:50-59. [PMID: 28711444 PMCID: PMC5792320 DOI: 10.1016/j.ab.2017.07.009] [Citation(s) in RCA: 1134] [Impact Index Per Article: 189.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Revised: 07/06/2017] [Accepted: 07/07/2017] [Indexed: 01/13/2023]
Abstract
The mitochondrial membrane potential (ΔΨm) generated by proton pumps (Complexes I, III and IV) is an essential component in the process of energy storage during oxidative phosphorylation. Together with the proton gradient (ΔpH), ΔΨm forms the transmembrane potential of hydrogen ions which is harnessed to make ATP. The levels of ΔΨm and ATP in the cell are kept relatively stable although there are limited fluctuations of both these factors that can occur reflecting normal physiological activity. However, sustained changes in both factors may be deleterious. A long-lasting drop or rise of ΔΨm vs normal levels may induce unwanted loss of cell viability and be a cause of various pathologies. Among other factors, ΔΨm plays a key role in mitochondrial homeostasis through selective elimination of dysfunctional mitochondria. It is also a driving force for transport of ions (other than H+) and proteins which are necessary for healthy mitochondrial functioning. We propose additional potential mechanisms for which ΔΨm is essential for maintenance of cellular health and viability and provide recommendations how to accurately measure ΔΨm in a cell and discuss potential sources of artifacts.
Collapse
Affiliation(s)
- Ljubava D Zorova
- A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russian Federation; International Laser Center, Lomonosov Moscow State University, Moscow, Russian Federation
| | - Vasily A Popkov
- A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russian Federation; Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, Russian Federation
| | - Egor Y Plotnikov
- A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russian Federation
| | - Denis N Silachev
- A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russian Federation
| | - Irina B Pevzner
- A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russian Federation
| | - Stanislovas S Jankauskas
- A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russian Federation
| | - Valentina A Babenko
- A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russian Federation; Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, Russian Federation
| | - Savva D Zorov
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, Russian Federation
| | - Anastasia V Balakireva
- Institute of Molecular Medicine, Sechenov First Moscow State Medical University, Moscow, Russian Federation
| | - Magdalena Juhaszova
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA
| | - Steven J Sollott
- Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA
| | - Dmitry B Zorov
- A.N. Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russian Federation; Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, Baltimore, MD, USA.
| |
Collapse
|
13
|
Chipot C, Dehez F, Schnell JR, Zitzmann N, Pebay-Peyroula E, Catoire LJ, Miroux B, Kunji ERS, Veglia G, Cross TA, Schanda P. Perturbations of Native Membrane Protein Structure in Alkyl Phosphocholine Detergents: A Critical Assessment of NMR and Biophysical Studies. Chem Rev 2018; 118:3559-3607. [PMID: 29488756 PMCID: PMC5896743 DOI: 10.1021/acs.chemrev.7b00570] [Citation(s) in RCA: 117] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Indexed: 12/25/2022]
Abstract
Membrane proteins perform a host of vital cellular functions. Deciphering the molecular mechanisms whereby they fulfill these functions requires detailed biophysical and structural investigations. Detergents have proven pivotal to extract the protein from its native surroundings. Yet, they provide a milieu that departs significantly from that of the biological membrane, to the extent that the structure, the dynamics, and the interactions of membrane proteins in detergents may considerably vary, as compared to the native environment. Understanding the impact of detergents on membrane proteins is, therefore, crucial to assess the biological relevance of results obtained in detergents. Here, we review the strengths and weaknesses of alkyl phosphocholines (or foscholines), the most widely used detergent in solution-NMR studies of membrane proteins. While this class of detergents is often successful for membrane protein solubilization, a growing list of examples points to destabilizing and denaturing properties, in particular for α-helical membrane proteins. Our comprehensive analysis stresses the importance of stringent controls when working with this class of detergents and when analyzing the structure and dynamics of membrane proteins in alkyl phosphocholine detergents.
Collapse
Affiliation(s)
- Christophe Chipot
- SRSMC, UMR 7019 Université de Lorraine CNRS, Vandoeuvre-les-Nancy F-54500, France
- Laboratoire
International Associé CNRS and University of Illinois at Urbana−Champaign, Vandoeuvre-les-Nancy F-54506, France
- Department
of Physics, University of Illinois at Urbana−Champaign, 1110 West Green Street, Urbana, Illinois 61801, United States
| | - François Dehez
- SRSMC, UMR 7019 Université de Lorraine CNRS, Vandoeuvre-les-Nancy F-54500, France
- Laboratoire
International Associé CNRS and University of Illinois at Urbana−Champaign, Vandoeuvre-les-Nancy F-54506, France
| | - Jason R. Schnell
- Department
of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
| | - Nicole Zitzmann
- Department
of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
| | | | - Laurent J. Catoire
- Laboratory
of Biology and Physico-Chemistry of Membrane Proteins, Institut de Biologie Physico-Chimique (IBPC), UMR
7099 CNRS, Paris 75005, France
- University
Paris Diderot, Paris 75005, France
- PSL
Research University, Paris 75005, France
| | - Bruno Miroux
- Laboratory
of Biology and Physico-Chemistry of Membrane Proteins, Institut de Biologie Physico-Chimique (IBPC), UMR
7099 CNRS, Paris 75005, France
- University
Paris Diderot, Paris 75005, France
- PSL
Research University, Paris 75005, France
| | - Edmund R. S. Kunji
- Medical
Research Council Mitochondrial Biology Unit, University of Cambridge, Cambridge CB2 0XY, United Kingdom
| | - Gianluigi Veglia
- Department
of Biochemistry, Molecular Biology, and Biophysics, and Department
of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Timothy A. Cross
- National
High Magnetic Field Laboratory, Florida
State University, Tallahassee, Florida 32310, United States
| | - Paul Schanda
- Université
Grenoble Alpes, CEA, CNRS, IBS, Grenoble F-38000, France
| |
Collapse
|
14
|
Kurauskas V, Hessel A, Ma P, Lunetti P, Weinhäupl K, Imbert L, Brutscher B, King MS, Sounier R, Dolce V, Kunji ERS, Capobianco L, Chipot C, Dehez F, Bersch B, Schanda P. How Detergent Impacts Membrane Proteins: Atomic-Level Views of Mitochondrial Carriers in Dodecylphosphocholine. J Phys Chem Lett 2018; 9:933-938. [PMID: 29397729 PMCID: PMC5834942 DOI: 10.1021/acs.jpclett.8b00269] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Accepted: 02/02/2018] [Indexed: 05/30/2023]
Abstract
Characterizing the structure of membrane proteins (MPs) generally requires extraction from their native environment, most commonly with detergents. Yet, the physicochemical properties of detergent micelles and lipid bilayers differ markedly and could alter the structural organization of MPs, albeit without general rules. Dodecylphosphocholine (DPC) is the most widely used detergent for MP structure determination by NMR, but the physiological relevance of several prominent structures has been questioned, though indirectly, by other biophysical techniques, e.g., functional/thermostability assay (TSA) and molecular dynamics (MD) simulations. Here, we resolve unambiguously this controversy by probing the functional relevance of three different mitochondrial carriers (MCs) in DPC at the atomic level, using an exhaustive set of solution-NMR experiments, complemented by functional/TSA and MD data. Our results provide atomic-level insight into the structure, substrate interaction and dynamics of the detergent-membrane protein complexes and demonstrates cogently that, while high-resolution NMR signals can be obtained for MCs in DPC, they systematically correspond to nonfunctional states.
Collapse
Affiliation(s)
- Vilius Kurauskas
- Université
Grenoble Alpes, CNRS, CEA, IBS, 38000 Grenoble, France
| | - Audrey Hessel
- Université
Grenoble Alpes, CNRS, CEA, IBS, 38000 Grenoble, France
| | - Peixiang Ma
- Université
Grenoble Alpes, CNRS, CEA, IBS, 38000 Grenoble, France
| | - Paola Lunetti
- Department
of Biological and Environmental Sciences and Technologies, University of Salento, 73100 Lecce, Italy
| | | | - Lionel Imbert
- Université
Grenoble Alpes, CNRS, CEA, IBS, 38000 Grenoble, France
| | | | - Martin S. King
- MRC-MBU, University of Cambridge, Cambridge CB2 0XY, United Kingdom
| | - Rémy Sounier
- CNRS,
INSERM, Université de Montpellier, 34094 Montpellier, France
| | - Vincenza Dolce
- Dept
of Pharmacy, University of Calabria, 87036 Arcavacata
di Rende, Italy
| | | | - Loredana Capobianco
- Department
of Biological and Environmental Sciences and Technologies, University of Salento, 73100 Lecce, Italy
| | - Christophe Chipot
- LPCT, UMR
7019 Université de Lorraine, CNRS and Laboratoire International
Associé & University of Illinois at Urbana−Champaign, F-54500 Vandoeuvre-lès-Nancy, France
| | - François Dehez
- LPCT, UMR
7019 Université de Lorraine, CNRS and Laboratoire International
Associé & University of Illinois at Urbana−Champaign, F-54500 Vandoeuvre-lès-Nancy, France
| | - Beate Bersch
- Université
Grenoble Alpes, CNRS, CEA, IBS, 38000 Grenoble, France
| | - Paul Schanda
- Université
Grenoble Alpes, CNRS, CEA, IBS, 38000 Grenoble, France
| |
Collapse
|
15
|
Wollenman LC, Vander Ploeg MR, Miller ML, Zhang Y, Bazil JN. The effect of respiration buffer composition on mitochondrial metabolism and function. PLoS One 2017; 12:e0187523. [PMID: 29091971 PMCID: PMC5665555 DOI: 10.1371/journal.pone.0187523] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 10/20/2017] [Indexed: 11/19/2022] Open
Abstract
Functional studies on isolated mitochondria critically rely on the right choice of respiration buffer. Differences in buffer composition can lead to dramatically different respiration rates leading to difficulties in comparing prior studies. The ideal buffer facilities high ADP-stimulated respiratory rates and minimizes substrate transport effects so that the ability to distinguish between various treatments and conditions is maximal. In this study, we analyzed a variety of respiration buffers and substrate combinations to determine the optimal conditions to support mitochondrial function through ADP-stimulated respiration and uncoupled respiration using FCCP. The buffers consisted of a standard KCl based buffer (B1) and three modified buffers with chloride replaced by the K-lactobionate, sucrose, and the antioxidant taurine (B2) or K-gluconate (B3). The fourth buffer (B4) was identical to B2 except that K-lactobionate was replaced with K-gluconate. The substrate combinations consisted of metabolites that utilize different pathways of mitochondrial metabolism. To test mitochondrial function, we used isolated cardiac guinea pig mitochondria and measured oxygen consumption for three respiratory states using an Oroboros Oxygraph-2k. These states were the leak state (energized mitochondria in the absence of adenylates), ADP-stimulated state (energized mitochondria in the presence of saturating ADP concentrations), and uncoupled state (energized mitochondria in the presence of FCCP). On average across all substrate combinations, buffers B2, B3, and B4 had an increase of 16%, 26%, and 35% for the leak state, ADP-simulated state, and uncoupled state, respectively, relative to rates using B1. The common feature distinguishing these buffers from B1 is the notable lack of high chloride concentrations. Based on the respiratory rate metrics obtained with the substrate combinations, we conclude that the adenine nucleotide translocase, the dicarboxylate carrier, and the alpha-ketoglutarate exchanger are partially inhibited by chloride. Therefore, when the goal is to maximize ADP-stimulated respiration, buffers containing K-lactobionate or K-gluconate are superior choices compared to the standard KCl-based buffers.
Collapse
Affiliation(s)
- Lucas C. Wollenman
- Department of Physiology, Michigan State University, East Lansing, MI, United States of America
- Vanderbilt University School of Medicine, Nashville, TN, United States of America
| | - Matthew R. Vander Ploeg
- Department of Physiology, Michigan State University, East Lansing, MI, United States of America
| | - Mackinzie L. Miller
- Biomedical Laboratory Diagnostics, Michigan State University, East Lansing, MI, United States of America
- Nephrology and Hypertension, Henry Ford Hospital, Detroit, MI, United States of America
| | - Yizhu Zhang
- Department of Physiology, Michigan State University, East Lansing, MI, United States of America
| | - Jason N. Bazil
- Department of Physiology, Michigan State University, East Lansing, MI, United States of America
| |
Collapse
|
16
|
Tamura K, Hayashi S. Atomistic modeling of alternating access of a mitochondrial ADP/ATP membrane transporter with molecular simulations. PLoS One 2017; 12:e0181489. [PMID: 28727843 PMCID: PMC5519185 DOI: 10.1371/journal.pone.0181489] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Accepted: 06/30/2017] [Indexed: 11/25/2022] Open
Abstract
The mitochondrial ADP/ATP carrier (AAC) is a membrane transporter that exchanges a cytosolic ADP for a matrix ATP. Atomic structures in an outward-facing (OF) form which binds an ADP from the intermembrane space have been solved by X-ray crystallography, and revealed their unique pseudo three-fold symmetry fold which is qualitatively different from pseudo two-fold symmetry of most transporters of which atomic structures have been solved. However, any atomic-level information on an inward-facing (IF) form, which binds an ATP from the matrix side and is fixed by binding of an inhibitor, bongkrekic acid (BA), is not available, and thus its alternating access mechanism for the transport process is unknown. Here, we report an atomic structure of the IF form predicted by atomic-level molecular dynamics (MD) simulations of the alternating access transition with a recently developed accelerating technique. We successfully obtained a significantly stable IF structure characterized by newly formed well-packed and -organized inter-domain interactions through the accelerated simulations of unprecedentedly large conformational changes of the alternating access without a prior knowledge of the target protein structure. The simulation also shed light on an atomistic mechanism of the strict transport selectivity of adenosine nucleotides over guanosine and inosine ones. Furthermore, the IF structure was shown to bind ATP and BA, and thus revealed their binding mechanisms. The present study proposes a qualitatively novel view of the alternating access of transporters having the unique three-fold symmetry in atomic details and opens the way for rational drug design targeting the transporter in the dynamic functional cycle.
Collapse
Affiliation(s)
- Koichi Tamura
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto, Japan
| | - Shigehiko Hayashi
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto, Japan
- * E-mail:
| |
Collapse
|
17
|
Vesicular nucleotide transporter (VNUT): appearance of an actress on the stage of purinergic signaling. Purinergic Signal 2017; 13:387-404. [PMID: 28616712 DOI: 10.1007/s11302-017-9568-1] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Accepted: 05/05/2017] [Indexed: 12/17/2022] Open
Abstract
Vesicular storage of ATP is one of the processes initiating purinergic chemical transmission. Although an active transport mechanism was postulated to be involved in the processes, a transporter(s) responsible for the vesicular storage of ATP remained unidentified for some time. In 2008, SLC17A9, the last identified member of the solute carrier 17 type I inorganic phosphate transporter family, was found to encode the vesicular nucleotide transporter (VNUT) that is responsible for the vesicular storage of ATP. VNUT transports various nucleotides in a membrane potential-dependent fashion and is expressed in the various ATP-secreting cells. Mice with knockout of the VNUT gene lose vesicular storage and release of ATP from neurons and neuroendocrine cells, resulting in blockage of the initiation of purinergic chemical transmission. Thus, VNUT plays an essential role in the vesicular storage and release of ATP. The VNUT knockout mice exhibit resistance for neuropathic pain and a therapeutic effect against diabetes by way of increased insulin sensitivity. Thus, VNUT inhibitors and suppression of VNUT gene expression may be used for therapeutic purposes through suppression of purinergic chemical transmission. This review summarizes the studies to date on VNUT and discusses what we have learned about the relevance of vesicular ATP release as a potential drug target.
Collapse
|
18
|
Siebels I, Dröse S. Charge translocation by mitochondrial NADH:ubiquinone oxidoreductase (complex I) from Yarrowia lipolytica measured on solid-supported membranes. Biochem Biophys Res Commun 2016; 479:277-282. [PMID: 27639643 DOI: 10.1016/j.bbrc.2016.09.059] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Accepted: 09/12/2016] [Indexed: 11/17/2022]
Abstract
The charge translocation by purified reconstituted mitochondrial complex I from the obligate aerobic yeast Yarrowia lipolytica was investigated after adsorption of proteoliposomes to solid-supported membranes. In presence of n-decylubiquinone (DBQ), pulses of NADH provided by rapid solution exchange induced charge transfer reflecting steady-state pumping activity of the reconstituted enzyme. The signal amplitude increased with time, indicating 'deactive→active' transition of the Yarrowia complex I. Furthermore, an increase of the membrane-conductivity after addition of 5-(N-ethyl-N-isopropyl)amiloride (EIPA) was detected which questiones the use of EIPA as an inhibitor of the Na+/H+-antiporter-like subunits of complex I. This investigation shows that electrical measurements on solid-supported membranes are a suitable method to analyze transport events and 'active/deactive' transition of mitochondrial complex I.
Collapse
Affiliation(s)
- Ilka Siebels
- Molecular Bioenergetics Group, Medical School, Johann Wolfgang Goethe-University, 60590, Frankfurt am Main, Germany; Goethe University Frankfurt, Institute of Organic Chemistry and Chemical Biology, Buchmann Institute for Molecular Life Sciences, Protein Reaction Control Group, Max-von-Laue-Str. 15, 60438, Frankfurt am Main, Germany
| | - Stefan Dröse
- Molecular Bioenergetics Group, Medical School, Johann Wolfgang Goethe-University, 60590, Frankfurt am Main, Germany; Department of Anesthesiology, Intensive-Care Medicine and Pain Therapy, University Hospital Frankfurt, 60590, Frankfurt am Main, Germany.
| |
Collapse
|
19
|
Grancara S, Dalla Via L, García-Argáez AN, Ohkubo S, Pacella E, Manente S, Bragadin M, Toninello A, Agostinelli E. Spermine cycling in mitochondria is mediated by adenine nucleotide translocase activity: mechanism and pathophysiological implications. Amino Acids 2016; 48:2327-37. [PMID: 27255894 DOI: 10.1007/s00726-016-2264-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 05/23/2016] [Indexed: 10/21/2022]
Abstract
Spermine, besides to be transported in mitochondria by an energy dependent electrophoretic mechanism, can be also released by two different mechanisms. The first one is induced in deenergizing conditions by FCCP or antimycin A and it is mediated by an electroneutral exchange spermine protons. The second one takes place in energizing conditions during the activity of the adenine nucleotide translocase and is mediated by an electroneutral symport mechanism involving the efflux in co-transport of spermine and phosphate and the exchange of exogenous ADP with endogenous ATP. The triggering of this mechanism permits an alternating cycling of spermine across the mitochondrial membrane, that is spermine is transported or released by energized mitochondria in the absence or presence of ATP synthesis, respectively. The physiological implications of this cycling of spermine are related to the induction or prevention of mitochondrial permeability transition and, consequently, on apoptosis or its prevention.
Collapse
Affiliation(s)
- Silvia Grancara
- Department of Biochemical Sciences, SAPIENZA University of Rome, Piazzale Aldo Moro 5, 00185, Rome, Italy
| | - Lisa Dalla Via
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua, Via F. Marzolo 5, 35131, Padua, Italy
| | - Aida Nelly García-Argáez
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua, Via F. Marzolo 5, 35131, Padua, Italy
| | - Shinji Ohkubo
- Department of Biochemical Sciences, SAPIENZA University of Rome, Piazzale Aldo Moro 5, 00185, Rome, Italy
| | - Elena Pacella
- Department of Sense Organs, Faculty Medicine and Dentistry, SAPIENZA University of Rome, Viale del Policlinico 155, 00161, Rome, Italy
| | - Sabrina Manente
- Department of Molecular Sciences and Nanosystems, Ca' Foscari University of Venice, Venice, Italy
| | - Marcantonio Bragadin
- Department of Molecular Sciences and Nanosystems, Ca' Foscari University of Venice, Venice, Italy
| | - Antonio Toninello
- Department of Biomedical Sciences, University of Padua, Viale U. Bassi 58 B, 35131, Padua, Italy. .,Department of Biomedical Sciences, University of Padua, Viale G. Colombo 3, 35131, Padua, Italy.
| | - Enzo Agostinelli
- Department of Biochemical Sciences, SAPIENZA University of Rome, Piazzale Aldo Moro 5, 00185, Rome, Italy
| |
Collapse
|
20
|
Oxenoid K, Chou JJ. A functional NMR for membrane proteins: dynamics, ligand binding, and allosteric modulation. Protein Sci 2016; 25:959-73. [PMID: 26928605 DOI: 10.1002/pro.2910] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Revised: 02/25/2016] [Accepted: 02/25/2016] [Indexed: 01/13/2023]
Abstract
By nature of conducting ions, transporting substrates and transducing signals, membrane channels, transporters and receptors are expected to exhibit intrinsic conformational dynamics. It is therefore of great interest and importance to understand the various properties of conformational dynamics acquired by these proteins, for example, the relative population of states, exchange rate, conformations of multiple states, and how small molecule ligands modulate the conformational exchange. Because small molecule binding to membrane proteins can be weak and/or dynamic, structural characterization of these effects is very challenging. This review describes several NMR studies of membrane protein dynamics, ligand-induced conformational rearrangements, and the effect of ligand binding on the equilibrium of conformational exchange. The functional significance of the observed phenomena is discussed.
Collapse
Affiliation(s)
- Kirill Oxenoid
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, 02115
| | - James J Chou
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, 02115
| |
Collapse
|
21
|
The transport mechanism of the mitochondrial ADP/ATP carrier. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:2379-93. [PMID: 27001633 DOI: 10.1016/j.bbamcr.2016.03.015] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Revised: 03/15/2016] [Accepted: 03/16/2016] [Indexed: 12/18/2022]
Abstract
The mitochondrial ADP/ATP carrier imports ADP from the cytosol and exports ATP from the mitochondrial matrix, which are key transport steps for oxidative phosphorylation in eukaryotic organisms. The transport protein belongs to the mitochondrial carrier family, a large transporter family in the inner membrane of mitochondria. It is one of the best studied members of the family and serves as a paradigm for the molecular mechanism of mitochondrial carriers. Structurally, the carrier consists of three homologous domains, each composed of two transmembrane α-helices linked with a loop and short α-helix on the matrix side. The transporter cycles between a cytoplasmic and matrix state in which a central substrate binding site is alternately accessible to these compartments for binding of ADP or ATP. On both the cytoplasmic and matrix side of the carrier are networks consisting of three salt bridges each. In the cytoplasmic state, the matrix salt bridge network is formed and the cytoplasmic network is disrupted, opening the central substrate binding site to the intermembrane space and cytosol, whereas the converse occurs in the matrix state. In the transport cycle, tighter substrate binding in the intermediate states allows the interconversion of conformations by lowering the energy barrier for disruption and formation of these networks, opening and closing the carrier to either side of the membrane in an alternating way. Conversion between cytoplasmic and matrix states might require the simultaneous rotation of three domains around a central translocation pathway, constituting a unique mechanism among transport proteins. This article is part of a Special Issue entitled: Mitochondrial Channels edited by Pierre Sonveaux, Pierre Maechler and Jean-Claude Martinou.
Collapse
|
22
|
Substrate-modulated ADP/ATP-transporter dynamics revealed by NMR relaxation dispersion. Nat Struct Mol Biol 2015; 22:636-41. [PMID: 26167881 PMCID: PMC4527935 DOI: 10.1038/nsmb.3059] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2015] [Accepted: 06/16/2015] [Indexed: 12/02/2022]
Abstract
The ADP/ATP carrier (AAC) transports ADP and ATP across the inner mitochondrial membrane. Unlike most transporters that have 2-fold direct or inverted quasi-symmetry, AAC has the apparent 3-fold rotational symmetry. Further, its transport rate is fast for transporters that carry large solutes. Here, we perform comprehensive NMR relaxation dispersion measurements for the yeast AAC carrier 3, which provide residue-specific information on the protein conformational exchange. Our data indicate that AAC is predominantly in the cytosol-facing open state and converts to a lowly populated state in an asymmetric manner despite its three-fold structural symmetry. Binding of the substrate ADP significantly increases the rate of conformational exchange, whereas the inhibitor CATR slows the exchange. These results suggest that while the transporter catalyzes the translocation of substrate, the substrate also facilitates interconversion between alternating states that may be relevant to the transport function.
Collapse
|
23
|
Monné M, Palmieri F. Antiporters of the mitochondrial carrier family. CURRENT TOPICS IN MEMBRANES 2014; 73:289-320. [PMID: 24745987 DOI: 10.1016/b978-0-12-800223-0.00008-6] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The eukaryotic transport protein family SLC25 consists of mitochondrial carriers (MCs) that are recognized on the sequence level by a threefold repeated and conserved signature motif. The majority of MCs characterized so far catalyzes strict exchanges of substrates across the mitochondrial inner membrane. The substrates are nucleotides, metabolic intermediates, and cofactors that are required in cytoplasmic and matrix metabolism. This review summarizes and discusses the current knowledge of the antiport mechanism(s) of MCs that has been deduced from determining transport characteristics and by analyzing structural, sequence, and mutagenesis data. The mode of transport varies among different MCs with respect to how the substrate translocation depends on the electrical and pH gradients across the mitochondrial inner membrane, for example, the ADP/ATP carrier is electrogenic (electrophoretic), the GTP/GDP carrier is dependent on the pH gradient, the aspartate/glutamate carrier is dependent on both, and the oxoglutarate/malate carrier is independent of them. The structure of the bovine ADP/ATP carrier consists of a six-transmembrane α-helix bundle with a pseudo-threefold symmetry and a closed matrix gate. By using this structure as a template in homology modeling, residues engaged in substrate binding and the formation of a cytoplasmic gate in MCs have been proposed. The functional importance of the residues of the binding site, the matrix, and the cytoplasmic gates is supported by transport activities of different MCs with single point mutations. Cumulative evidence has been used to postulate a general transport mechanism for MCs.
Collapse
Affiliation(s)
- Magnus Monné
- Department of Biosciences, Biotechnology and Biopharmaceutics, Laboratory of Biochemistry and Molecular Biology, University of Bari, Bari, Italy; Department of Sciences, University of Basilicata, Potenza, Italy
| | - Ferdinando Palmieri
- Department of Biosciences, Biotechnology and Biopharmaceutics, Laboratory of Biochemistry and Molecular Biology, University of Bari, Bari, Italy.
| |
Collapse
|
24
|
Stock U, Matter H, Diekert K, Dörner W, Dröse S, Licher T. Measuring interference of drug-like molecules with the respiratory chain: toward the early identification of mitochondrial uncouplers in lead finding. Assay Drug Dev Technol 2013; 11:408-22. [PMID: 23992120 PMCID: PMC3777647 DOI: 10.1089/adt.2012.463] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The electron transport chain (ETC) couples electron transfer between donors and acceptors with proton transport across the inner mitochondrial membrane. The resulting electrochemical proton gradient is used to generate chemical energy in the form of adenosine triphosphate (ATP). Proton transfer is based on the activity of complex I-V proteins in the ETC. The overall electrical activity of these proteins can be measured by proton transfer using Solid Supported Membrane technology. We tested the activity of complexes I, III, and V in a combined assay, called oxidative phosphorylation assay (oxphos assay), by activating each complex with the corresponding substrate. The oxphos assay was used to test in-house substances from different projects and several drugs currently available on the market that have reported effects on mitochondrial functions. The resulting data were compared to the influence of the respective compounds on mitochondria as determined by oxygen consumption and to data generated with an ATP depletion assay. The comparison shows that the oxidative phosphorylation assay provides both a rapid approach for detecting interaction of compounds with respiratory chain proteins and information on their mode of interaction. Therefore, the oxphos assay is a useful tool to support structure activity relationship studies by allowing early identification of mitotoxicity and for analyzing the outcome of phenotypic screens that are susceptible to the generation of mitotoxicity-related artifacts.
Collapse
Affiliation(s)
- Ursula Stock
- R&D LGCR, Sanofi-Aventis Deutschland GmbH, Frankfurt, Germany
| | - Hans Matter
- R&D LGCR, Sanofi-Aventis Deutschland GmbH, Frankfurt, Germany
| | | | | | - Stefan Dröse
- ZBC-Molekulare Bioenergetik, Frankfurt University Hospital, Frankfurt, Germany
| | - Thomas Licher
- R&D LGCR, Sanofi-Aventis Deutschland GmbH, Frankfurt, Germany
| |
Collapse
|
25
|
Boelens AD, Pradhan RK, Blomeyer CA, Camara AKS, Dash RK, Stowe DF. Extra-matrix Mg2+ limits Ca2+ uptake and modulates Ca2+ uptake-independent respiration and redox state in cardiac isolated mitochondria. J Bioenerg Biomembr 2013; 45:203-18. [PMID: 23456198 DOI: 10.1007/s10863-013-9500-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Accepted: 01/24/2013] [Indexed: 12/20/2022]
Abstract
Cardiac mitochondrial matrix (m) free Ca(2+) ([Ca(2+)]m) increases primarily by Ca(2+) uptake through the Ca(2+) uniporter (CU). Ca(2+) uptake via the CU is attenuated by extra-matrix (e) Mg(2+) ([Mg(2+)]e). How [Ca(2+)]m is dynamically modulated by interacting physiological levels of [Ca(2+)]e and [Mg(2+)]e and how this interaction alters bioenergetics are not well understood. We postulated that as [Mg(2+)]e modulates Ca(2+) uptake via the CU, it also alters bioenergetics in a matrix Ca(2+)-induced and matrix Ca(2+)-independent manner. To test this, we measured changes in [Ca(2+)]e, [Ca(2+)]m, [Mg(2+)]e and [Mg(2+)]m spectrofluorometrically in guinea pig cardiac mitochondria in response to added CaCl2 (0-0.6 mM; 1 mM EGTA buffer) with/without added MgCl2 (0-2 mM). In parallel, we assessed effects of added CaCl2 and MgCl2 on NADH, membrane potential (ΔΨm), and respiration. We found that ≥0.125 mM MgCl2 significantly attenuated CU-mediated Ca(2+) uptake and [Ca(2+)]m. Incremental [Mg(2+)]e did not reduce initial Ca(2+)uptake but attenuated the subsequent slower Ca(2+) uptake, so that [Ca(2+)]m remained unaltered over time. Adding CaCl2 without MgCl2 to attain a [Ca(2+)]m from 46 to 221 nM enhanced state 3 NADH oxidation and increased respiration by 15 %; up to 868 nM [Ca(2+)]m did not additionally enhance NADH oxidation or respiration. Adding MgCl2 did not increase [Mg(2+)]m but it altered bioenergetics by its direct effect to decrease Ca(2+) uptake. However, at a given [Ca(2+)]m, state 3 respiration was incrementally attenuated, and state 4 respiration enhanced, by higher [Mg(2+)]e. Thus, [Mg(2+)]e without a change in [Mg(2+)]m can modulate bioenergetics independently of CU-mediated Ca(2+) transport.
Collapse
Affiliation(s)
- Age D Boelens
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | | | | | | | | | | |
Collapse
|
26
|
Allouche M, Pertuiset C, Robert JL, Martel C, Veneziano R, Henry C, dein OSE, Saint N, Brenner C, Chopineau J. ANT-VDAC1 interaction is direct and depends on ANT isoform conformation in vitro. Biochem Biophys Res Commun 2012; 429:12-7. [PMID: 23131554 DOI: 10.1016/j.bbrc.2012.10.108] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 10/16/2012] [Indexed: 10/27/2022]
Abstract
The voltage-dependent anion channel (VDAC) and the adenine nucleotide translocase (ANT) have central roles in mitochondrial functions such as nucleotides transport and cell death. The interaction between VDAC, an outer mitochondrial membrane protein and ANT, an inner membrane protein, was studied in isolated mitochondria and in vitro. Both proteins were isolated from various mitochondrial sources and reconstituted in vitro using a biomimetic system composed of recombinant human VDAC isoform 1 (rhVDAC1) immobilized on a surface plasmon resonance (SPR) sensor chip surface. Two enriched-preparations of (H)ANT (ANT from heart, mainly ANT1) and (L)ANT (ANT from liver, mainly ANT2) isoforms interacted differently with rhVDAC1. Moreover, the pharmacological ANT inhibitors atractyloside and bongkrekic acid modulated this interaction. Thus, ANT-VDAC interaction depends both on ANT isoform identity and on the conformation of ANT.
Collapse
|
27
|
Long AR, O'Brien CC, Alder NN. The cell-free integration of a polytopic mitochondrial membrane protein into liposomes occurs cotranslationally and in a lipid-dependent manner. PLoS One 2012; 7:e46332. [PMID: 23050015 PMCID: PMC3457961 DOI: 10.1371/journal.pone.0046332] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Accepted: 08/31/2012] [Indexed: 01/19/2023] Open
Abstract
The ADP/ATP Carrier (AAC) is the most abundant transporter of the mitochondrial inner membrane. The central role that this transporter plays in cellular energy production highlights the importance of understanding its structure, function, and the basis of its pathologies. As a means of preparing proteoliposomes for the study of membrane proteins, several groups have explored the use of cell-free translation systems to facilitate membrane protein integration directly into preformed unilamellar vesicles without the use of surfactants. Using AAC as a model, we report for the first time the detergent-free reconstitution of a mitochondrial inner membrane protein into liposomes using a wheat germ-based in vitro translation system. Using a host of independent approaches, we demonstrate the efficient integration of AAC into vesicles with an inner membrane-mimetic lipid composition and, more importantly, that the integrated AAC is functionally active in transport. By adding liposomes at different stages of the translation reaction, we show that this direct integration is obligatorily cotranslational, and by synthesizing stable ribosome-bound nascent chain intermediates, we show that the nascent AAC polypeptide interacts with lipid vesicles while ribosome-bound. Finally, we show that the presence of the phospholipid cardiolipin in the liposomes specifically enhances AAC translation rate as well as the efficiency of vesicle association and integration. In light of these results, the possible mechanisms of liposome-assisted membrane protein integration during cell-free translation are discussed with respect to the mode of integration and the role of specific lipids.
Collapse
Affiliation(s)
- Ashley R. Long
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut, United States of America
| | - Catherine C. O'Brien
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut, United States of America
| | - Nathan N. Alder
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut, United States of America
| |
Collapse
|
28
|
Miyaji T, Sawada K, Omote H, Moriyama Y. Divalent cation transport by vesicular nucleotide transporter. J Biol Chem 2011; 286:42881-7. [PMID: 22052906 DOI: 10.1074/jbc.m111.277269] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The vesicular nucleotide transporter (VNUT) is a secretory vesicle protein that is responsible for the vesicular storage and subsequent exocytosis of ATP (Sawada, K., Echigo, N., Juge, N., Miyaji, T., Otsuka, M., Omote, H., and Moriyama, Y. (2008) Proc. Natl. Acad. Sci. U.S.A. 105, 5683-5686). Because VNUT actively transports ATP in a membrane potential (Δψ)-dependent manner irrespective of divalent cations such as Mg(2+) and Ca(2+), VNUT recognizes free ATP as a transport substrate. However, whether or not VNUT transports chelating complexes with divalent cations remains unknown. Here, we show that proteoliposomes containing purified VNUT actively took up Mg(2+) when ATP was present, as detected by atomic absorption spectroscopy. The VNUT-containing proteoliposomes also took up radioactive Ca(2+) upon imposing Δψ (positive-inside) but not ΔpH. The Δψ-driven Ca(2+) uptake required ATP and a millimolar concentration of Cl(-), which was inhibited by Evans blue, a specific inhibitor of SLC17-type transporters. VNUT in which Arg-119 was specifically mutated to alanine, the counterpart of the essential amino acid residue of the SLC17 family, lost the ability to take up both ATP and Ca(2+). Ca(2+) uptake was also inhibited in the presence of various divalent cations such as Mg(2+). Kinetic analysis indicated that Ca(2+) or Mg(2+) did not affect the apparent affinity for ATP. RNAi of the VNUT gene in PC12 cells decreased the vesicular Mg(2+) concentration to 67.7%. These results indicate that VNUT transports both nucleotides and divalent cations probably as chelating complexes and suggest that VNUT functions as a divalent cation importer in secretory vesicles under physiological conditions.
Collapse
Affiliation(s)
- Takaaki Miyaji
- Advanced Science Research Center, Okayama University, Okayama 700-8530, Japan
| | | | | | | |
Collapse
|
29
|
Spetea C, Schoefs B. Solute transporters in plant thylakoid membranes: Key players during photosynthesis and light stress. Commun Integr Biol 2011; 3:122-9. [PMID: 20585503 DOI: 10.4161/cib.3.2.10909] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2009] [Accepted: 12/09/2009] [Indexed: 11/19/2022] Open
Abstract
Plants utilize sunlight to drive photosynthetic energy conversion in the chloroplast thylakoid membrane. Here are located four major photosynthetic complexes, about which we have great knowledge in terms of structure and function. However, much less we know about auxiliary proteins, such as transporters, ensuring an optimum function and turnover of these complexes. The most prominent thylakoid transporter is the proton-translocating ATP-synthase. Recently, four additional transporters have been identified in the thylakoid membrane of Arabidopsis thaliana, namely one copper-transporting P-ATPase, one chloride channel, one phosphate transporter, and one ATP/ADP carrier. Here, we review the current knowledge on the function and physiological role of these transporters during photosynthesis and light stress in plants. Subsequently, we make a survey on the outlook of thylakoid activities awaiting identification of responsible proteins. Such knowledge is necessary to understand the thylakoid network of transporters, and to design strategies for bioengineering crop plants in the future.
Collapse
|
30
|
Klimenko ES, Mileiko VA, Morozkin ES, Laktionov PP, Konstantinov YM. Study of DNA import and export in potato (Solanum tuberosum) mitochondria using quantitative PCR. BIOCHEMISTRY MOSCOW SUPPLEMENT SERIES A-MEMBRANE AND CELL BIOLOGY 2011. [DOI: 10.1134/s1990747811030044] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
31
|
Watzke N, Diekert K, Obrdlik P. Electrophysiology of respiratory chain complexes and the ADP-ATP exchanger in native mitochondrial membranes. Biochemistry 2010; 49:10308-18. [PMID: 20958090 DOI: 10.1021/bi1011755] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Transport of protons and solutes across mitochondrial membranes is essential for many physiological processes. However, neither the proton-pumping respiratory chain complexes nor the mitochondrial secondary active solute transport proteins have been characterized electrophysiologically in their native environment. In this study, solid-supported membrane (SSM) technology was applied for electrical measurements of respiratory chain complexes CI, CII, CIII, and CIV, the F(O)F(1)-ATPase/synthase (CV), and the adenine nucleotide translocase (ANT) in inner membranes of pig heart mitochondria. Specific substrates and inhibitors were used to validate the different assays, and the corresponding K(0.5) and IC(50) values were in good agreement with previously published results obtained with other methods. In combined measurements of CI-CV, it was possible to detect oxidative phosphorylation (OXPHOS), to measure differential effects of the uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP) on the respective protein activities, and to determine the corresponding IC(50) values. Moreover, the measurements revealed a tight functional coupling of CI and CIII. Coenzyme Q (CoQ) analogues decylubiquinone (DBQ) and idebenone (Ide) stimulated the CII- and CIII-specific electrical currents but had inverse effects on CI-CIII activity. In summary, the results describe the electrophysiological and pharmacological properties of respiratory chain complexes, OXPHOS, and ANT in native mitochondrial membranes and demonstrate that SSM-based electrophysiology provides new insights into a complex molecular mechanism of the respiratory chain and the associated transport proteins. Besides, the SSM-based approach is suited for highly sensitive and specific testing of diverse respiratory chain modulators such as inhibitors, CoQ analogues, and uncoupling agents.
Collapse
Affiliation(s)
- Natalie Watzke
- IonGate Biosciences GmbH, Industriepark Hoechst, Frankfurt am Main, Germany
| | | | | |
Collapse
|
32
|
Yin L, Lundin B, Bertrand M, Nurmi M, Solymosi K, Kangasjärvi S, Aro EM, Schoefs B, Spetea C. Role of thylakoid ATP/ADP carrier in photoinhibition and photoprotection of photosystem II in Arabidopsis. PLANT PHYSIOLOGY 2010; 153:666-77. [PMID: 20357135 PMCID: PMC2879782 DOI: 10.1104/pp.110.155804] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The chloroplast thylakoid ATP/ADP carrier (TAAC) belongs to the mitochondrial carrier superfamily and supplies the thylakoid lumen with stromal ATP in exchange for ADP. Here, we investigate the physiological consequences of TAAC depletion in Arabidopsis (Arabidopsis thaliana). We show that the deficiency of TAAC in two T-DNA insertion lines does not modify the chloroplast ultrastructure, the relative amounts of photosynthetic proteins, the pigment composition, and the photosynthetic activity. Under growth light conditions, the mutants initially displayed similar shoot weight, but lower when reaching full development, and were less tolerant to high light conditions in comparison with the wild type. These observations prompted us to study in more detail the effects of TAAC depletion on photoinhibition and photoprotection of the photosystem II (PSII) complex. The steady-state phosphorylation levels of PSII proteins were not affected, but the degradation of the reaction center II D1 protein was blocked, and decreased amounts of CP43-less PSII monomers were detected in the mutants. Besides this, the mutant leaves displayed a transiently higher nonphotochemical quenching of chlorophyll fluorescence than the wild-type leaves, especially at low light. This may be attributed to the accumulation in the absence of TAAC of a higher electrochemical H(+) gradient in the first minutes of illumination, which more efficiently activates photoprotective xanthophyll cycle-dependent and independent mechanisms. Based on these results, we propose that TAAC plays a critical role in the disassembly steps during PSII repair and in addition may balance the trans-thylakoid electrochemical H(+) gradient storage.
Collapse
|
33
|
Kunji ERS, Crichton PG. Mitochondrial carriers function as monomers. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1797:817-31. [PMID: 20362544 DOI: 10.1016/j.bbabio.2010.03.023] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2010] [Revised: 03/05/2010] [Accepted: 03/25/2010] [Indexed: 10/19/2022]
Abstract
Mitochondrial carriers link biochemical pathways in the mitochondrial matrix and cytosol by transporting metabolites, inorganic ions, nucleotides and cofactors across the mitochondrial inner membrane. Uncoupling proteins that dissipate the proton electrochemical gradient also belong to this protein family. For almost 35 years the general consensus has been that mitochondrial carriers are dimeric in structure and function. This view was based on data from inhibitor binding studies, small-angle neutron scattering, electron microscopy, differential tagging/affinity chromatography, size-exclusion chromatography, analytical ultracentrifugation, native gel electrophoresis, cross-linking experiments, tandem-fusions, negative dominance studies and mutagenesis. However, the structural folds of the ADP/ATP carriers were found to be monomeric, lacking obvious dimerisation interfaces. Subsequently, the yeast ADP/ATP carrier was demonstrated to function as a monomer. Here, we revisit the data that have been published in support of a dimeric state of mitochondrial carriers. Our analysis shows that when critical factors are taken into account, the monomer is the only plausible functional form of mitochondrial carriers. We propose a transport model based on the monomer, in which access to a single substrate binding site is controlled by two flanking salt bridge networks, explaining uniport and strict exchange of substrates.
Collapse
Affiliation(s)
- Edmund R S Kunji
- The Medical Research Council, Mitochondrial Biology Unit, Hills Road, Cambridge, CB2 0XY, UK.
| | | |
Collapse
|
34
|
Krammer EM, Ravaud S, Dehez F, Frelet-Barrand A, Pebay-Peyroula E, Chipot C. High-chloride concentrations abolish the binding of adenine nucleotides in the mitochondrial ADP/ATP carrier family. Biophys J 2010; 97:L25-7. [PMID: 19917217 DOI: 10.1016/j.bpj.2009.08.047] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2009] [Revised: 08/12/2009] [Accepted: 08/20/2009] [Indexed: 10/20/2022] Open
Abstract
The ADP/ATP carrier (AAC) is a very effective membrane protein that mediates the exchange of ADP and ATP across the mitochondrial membrane. In vivo transport measurements on the AAC overexpressed in Escherichia coli demonstrate that this process can be severely inhibited by high-chloride concentrations. Molecular-dynamics simulations reveal a strong modification of the topology of the local electric field related to the number of chloride ions inside the cavity. Halide ions are shown to shield the positive charges lining the internal cavity of the carrier by accurate targeting of key basic residues. These specific amino acids are highly conserved as highlighted by the analysis of multiple AAC sequences. These results strongly suggest that the chloride concentration acts as an electrostatic lock for the mitochondrial AAC family, thereby preventing adenine nucleotides from reaching their dedicated binding sites.
Collapse
Affiliation(s)
- Eva-Maria Krammer
- Equipe de Dynamique des Assemblages Membranaires, UMR No. 7565, Centre National de la Recherche Scientifique-Université Henri Poincaré, Nancy, France
| | | | | | | | | | | |
Collapse
|
35
|
McLuskey K, Roszak AW, Zhu Y, Isaacs NW. Crystal structures of all-alpha type membrane proteins. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2009; 39:723-55. [DOI: 10.1007/s00249-009-0546-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2009] [Revised: 08/19/2009] [Accepted: 08/26/2009] [Indexed: 01/05/2023]
|
36
|
A novel kinetic assay of mitochondrial ATP-ADP exchange rate mediated by the ANT. Biophys J 2009; 96:2490-504. [PMID: 19289073 DOI: 10.1016/j.bpj.2008.12.3915] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2008] [Revised: 12/08/2008] [Accepted: 12/17/2008] [Indexed: 11/23/2022] Open
Abstract
A novel method exploiting the differential affinity of ADP and ATP to Mg(2+) was developed to measure mitochondrial ADP-ATP exchange rate. The rate of ATP appearing in the medium after addition of ADP to energized mitochondria, is calculated from the measured rate of change in free extramitochondrial [Mg(2+)] reported by the membrane-impermeable 5K(+) salt of the Mg(2+)-sensitive fluorescent indicator, Magnesium Green, using standard binding equations. The assay is designed such that the adenine nucleotide translocase (ANT) is the sole mediator of changes in [Mg(2+)] in the extramitochondrial volume, as a result of ADP-ATP exchange. We also provide data on the dependence of ATP efflux rate within the 6.8-7.8 matrix pH range as a function of membrane potential. Finally, by comparing the ATP-ADP steady-state exchange rate to the amount of the ANT in rat brain synaptic, brain nonsynaptic, heart and liver mitochondria, we provide molecular turnover numbers for the known ANT isotypes.
Collapse
|
37
|
Johnston JM, Khalid S, Sansom MSP. Conformational dynamics of the mitochondrial ADP/ATP carrier: a simulation study. Mol Membr Biol 2009; 25:506-17. [PMID: 18988066 DOI: 10.1080/09687680802459271] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The mitochondrial ADP/ATP carrier is a six helix bundle membrane transport protein, which couples the exit of ATP from the mitochondrial matrix to the entry of ADP. Extended (4x20 ns) molecular dynamics simulations of the carrier, in the presence and absence of bound inhibitor (carboxyatractyloside), have been used to explore the conformational dynamics of the protein in a lipid bilayer environment, in the presence and absence of the carboxyatractyloside inhibitor. The dynamic flexibility (measured as conformational drift and fluctuations) of the protein is reduced in the presence of bound inhibitor. Proline residues in transmembrane helices H1, H3 and H5 appear to form dynamic hinges. Fluctuations in inter-helix salt bridges are also observed over the time course of the simulations. Inhibitor-protein and lipid-protein interactions have been characterised in some detail. Overall, the simulations support a transport mechanism in which flexibility about the proline hinges enables a transition between a 'closed' and an 'open' pore-like state of the carrier protein.
Collapse
|
38
|
Nury H, Manon F, Arnou B, le Maire M, Pebay-Peyroula E, Ebel C. Mitochondrial Bovine ADP/ATP Carrier in Detergent Is Predominantly Monomeric but Also Forms Multimeric Species. Biochemistry 2008; 47:12319-31. [DOI: 10.1021/bi801053m] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hugues Nury
- CEA, DSV, and CNRS and Université Joseph Fourier, Institut de Biologie Structurale, 41 rue Jules Horowitz, F-38027, Grenoble, France, Institut de Biochimie et Génétique Cellulaires, CNRS UMR 5095, Université Bordeaux 2, F-33077 Bordeaux Cedex, France, and CEA, Institut de Biologie et Technologies de Saclay, and CNRS URA 2096 and Université Paris-Sud 11, LRA 17V, F-91191 Gif-sur-Yvette, France
| | - Florence Manon
- CEA, DSV, and CNRS and Université Joseph Fourier, Institut de Biologie Structurale, 41 rue Jules Horowitz, F-38027, Grenoble, France, Institut de Biochimie et Génétique Cellulaires, CNRS UMR 5095, Université Bordeaux 2, F-33077 Bordeaux Cedex, France, and CEA, Institut de Biologie et Technologies de Saclay, and CNRS URA 2096 and Université Paris-Sud 11, LRA 17V, F-91191 Gif-sur-Yvette, France
| | - Bertrand Arnou
- CEA, DSV, and CNRS and Université Joseph Fourier, Institut de Biologie Structurale, 41 rue Jules Horowitz, F-38027, Grenoble, France, Institut de Biochimie et Génétique Cellulaires, CNRS UMR 5095, Université Bordeaux 2, F-33077 Bordeaux Cedex, France, and CEA, Institut de Biologie et Technologies de Saclay, and CNRS URA 2096 and Université Paris-Sud 11, LRA 17V, F-91191 Gif-sur-Yvette, France
| | - Marc le Maire
- CEA, DSV, and CNRS and Université Joseph Fourier, Institut de Biologie Structurale, 41 rue Jules Horowitz, F-38027, Grenoble, France, Institut de Biochimie et Génétique Cellulaires, CNRS UMR 5095, Université Bordeaux 2, F-33077 Bordeaux Cedex, France, and CEA, Institut de Biologie et Technologies de Saclay, and CNRS URA 2096 and Université Paris-Sud 11, LRA 17V, F-91191 Gif-sur-Yvette, France
| | - Eva Pebay-Peyroula
- CEA, DSV, and CNRS and Université Joseph Fourier, Institut de Biologie Structurale, 41 rue Jules Horowitz, F-38027, Grenoble, France, Institut de Biochimie et Génétique Cellulaires, CNRS UMR 5095, Université Bordeaux 2, F-33077 Bordeaux Cedex, France, and CEA, Institut de Biologie et Technologies de Saclay, and CNRS URA 2096 and Université Paris-Sud 11, LRA 17V, F-91191 Gif-sur-Yvette, France
| | - Christine Ebel
- CEA, DSV, and CNRS and Université Joseph Fourier, Institut de Biologie Structurale, 41 rue Jules Horowitz, F-38027, Grenoble, France, Institut de Biochimie et Génétique Cellulaires, CNRS UMR 5095, Université Bordeaux 2, F-33077 Bordeaux Cedex, France, and CEA, Institut de Biologie et Technologies de Saclay, and CNRS URA 2096 and Université Paris-Sud 11, LRA 17V, F-91191 Gif-sur-Yvette, France
| |
Collapse
|
39
|
Cherepanov AV, Doroshenko EV, Matysik J, de Vries S, De Groot HJM. A view on phosphate ester photochemistry by time-resolved solid state NMR. Intramolecular redox reaction of caged ATP. Phys Chem Chem Phys 2008; 10:6820-8. [PMID: 19015786 DOI: 10.1039/b806677a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The light-driven intramolecular redox reaction of adenosine-5'-triphosphate-[P3-(1-(2-nitrophenyl)-ethyl)]ester (caged ATP) has been studied in frozen aqueous solution using time-resolved solid state NMR spectroscopy under continuous illumination conditions. Cleavage of the phosphate ester bond leads to 0.3, 1.36, and 6.06 ppm downfield shifts of the alpha-, beta-, and gamma-phosphorus resonances of caged ATP, respectively. The observed rate of ATP formation is 2.4 +/- 0.2 h(-1) at 245 K. The proton released in the reaction binds to the triphosphate moiety of the nascent ATP, causing the upfield shifts of the 31P resonances. Analyses of the reaction kinetics indicate that bond cleavage and proton release are two sequential processes in the solid state, suggesting that the 1-hydroxy,1-(2-nitrosophenyl)-ethyl carbocation intermediate is involved in the reaction. The beta-phosphate oxygen atom of ATP is protonated first, indicating its proximity to the reaction center, possibly within hydrogen bonding distance. The residual linewidth kinetics are interpreted in terms of chemical exchange processes, hydrogen bonding of the beta-phosphate oxygen atom and evolution of the hydrolytic equilibrium at the triphosphate moiety of the nascent ATP. Photoreaction of caged ATP in situ gives an opportunity to study structural kinetics and catalysis of ATP-dependent enzymes by NMR spectroscopy in rotating solids.
Collapse
Affiliation(s)
- Alexey V Cherepanov
- Biophysical Organic Chemistry/Solid State NMR group, Leiden Institute of Chemistry, Faculty of Mathematics and Natural Sciences, Leiden University, Einsteinweg 55, 2333 CC, Leiden, The Netherlands.
| | | | | | | | | |
Collapse
|
40
|
Dehez F, Pebay-Peyroula E, Chipot C. Binding of ADP in the mitochondrial ADP/ATP carrier is driven by an electrostatic funnel. J Am Chem Soc 2008; 130:12725-33. [PMID: 18729359 DOI: 10.1021/ja8033087] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The ADP/ATP carrier (AAC) is a membrane protein of paramount importance for the energy-fueling function of the mitochondria, transporting ADP from the intermembrane space to the matrix and ATP in the opposite direction. On the basis of the high-resolution, 2.2-A structure of the bovine carrier, a total of 0.53 micros of classical molecular dynamics simulations were conducted in a realistic membrane environment to decipher the early events of ADP (3-) translocation across the inner membrane of the mitochondria. Examination of apo-AAC underscores the impermeable nature of the carrier, impeding passive transport of permeants toward the matrix. The electrostatic funnel illuminated from three-dimensional mapping of the electrostatic potential forms a privileged passageway anticipated to drive the diphosphate nucleotide rapidly toward the bottom of the internal cavity. This conjecture is verified in the light of repeated, independent numerical experiments, whereby the permeant is dropped near the mouth of the mitochondrial carrier. Systematic association of ADP (3-) to the crevice of the AAC, an early event in its transport across the inner membrane, is accompanied by the formation of an intricate network of noncovalent bonds. Simulations relying on the use of an adaptive biasing force reveal for the first time that the proposed binding site corresponds to a minimum of the free energy landscape delineating the translocation of ADP (3-) in the carrier. The present work paves the way to the design of novel nucleotides and new experiments aimed at unveiling key structural features in the chronology of ADP/ATP transport across the mitochondrial membrane.
Collapse
Affiliation(s)
- François Dehez
- Equipe de dynamique des assemblages membranaires, UMR No. 7565 CNRS-UHP, Nancy Université, BP 239, 54506 Vandoeuvre-lès-Nancy cedex, France
| | | | | |
Collapse
|
41
|
Hong J, Samudio I, Chintharlapalli S, Safe S. 1,1-bis(3'-indolyl)-1-(p-substituted phenyl)methanes decrease mitochondrial membrane potential and induce apoptosis in endometrial and other cancer cell lines. Mol Carcinog 2008; 47:492-507. [PMID: 18085536 DOI: 10.1002/mc.20407] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
1,1-Bis(3'-indolyl)-1-(p-substituted phenyl)methanes, containing p-t-butyl (DIM-C-pPhtBu) and phenyl (DIM-C-pPhC(6)H(5)) substituents, are peroxisome proliferator-activated receptor gamma (PPARgamma) agonists; however, DIM-C-pPhtBu-induced growth inhibition and cell death in human HEC1A endometrial cancer cells is PPARgamma-independent. DIM-C-pPhtBu decreased mitochondrial membrane potential (MMP) and promoted the release of cytochrome c and caspase activation and nuclear uptake of endonuclease G leading to apoptosis of HEC1A cells. DIM-C-pPhtBu specifically targeted the mitochondrial permeability transition pore complex (PTPC) because the DIM-C-pPhtBu-induced pro-apoptotic responses were inhibited by atractyloside (Atra), a compound that specifically interacts with the inner mitochondrial membrane adenine nucleotide transport (ANT) proteins. At the dose of Atra used in this study (300 microM), this compound alone did not alter the PTPC but inhibited the mitochondriotoxic effects of DIM-C-pPhtBu. DIM-C-pPhtBu/DIM-C-pPhC(6)H(5) and Atra also differentially affected the ability of eosin-5-maleimide (EMA) to alkylate Cys160 in the ANT protein and Atra, but not DIM-C-pPhtBu, inhibited the exchange of ATP/ADP in isolated mitochondria suggesting that these pharmacophores act on different sites on the ANT protein. Results of this study show that the receptor-independent proapoptotic activity of DIM-C-pPhtBu and DIM-C-pPhC(6)H(5) were related to novel mitochondriotoxic activities involving inner mitochondrial ANT proteins.
Collapse
Affiliation(s)
- Jun Hong
- Institute of Biosciences and Technology, Texas A&M University System Health Science Center, Houston, Texas 77843-4466, USA
| | | | | | | |
Collapse
|
42
|
Klingenberg M. The ADP and ATP transport in mitochondria and its carrier. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:1978-2021. [PMID: 18510943 DOI: 10.1016/j.bbamem.2008.04.011] [Citation(s) in RCA: 461] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 10/04/2007] [Revised: 04/24/2008] [Accepted: 04/24/2008] [Indexed: 10/22/2022]
Abstract
Different from some more specialised short reviews, here a general although not encyclopaedic survey of the function, metabolic role, structure and mechanism of the ADP/ATP transport in mitochondria is presented. The obvious need for an "old fashioned" review comes from the gateway role in metabolism of the ATP transfer to the cytosol from mitochondria. Amidst the labours, 40 or more years ago, of unravelling the role of mitochondrial compartments and of the two membranes, the sequence of steps of how ATP arrives in the cytosol became a major issue. When the dust settled, a picture emerged where ATP is exported across the inner membrane in a 1:1 exchange against ADP and where the selection of ATP versus ADP is controlled by the high membrane potential at the inner membrane, thus uplifting the free energy of ATP in the cytosol over the mitochondrial matrix. Thus the disparate energy and redox states of the two major compartments are bridged by two membrane potential responsive carriers to enable their symbiosis in the eukaryotic cell. The advance to the molecular level by studying the binding of nucleotides and inhibitors was facilitated by the high level of carrier (AAC) binding sites in the mitochondrial membrane. A striking flexibility of nucleotide binding uncovered the reorientation of carrier sites between outer and inner face, assisted by the side specific high affinity inhibitors. The evidence of a single carrier site versus separate sites for substrate and inhibitors was expounded. In an ideal setting principles of transport catalysis were elucidated. The isolation of intact AAC as a first for any transporter enabled the reconstitution of transport for unravelling, independently of mitochondrial complications, the factors controlling the ADP/ATP exchange. Electrical currents measured with the reconstituted AAC demonstrated electrogenic translocation and charge shift of reorienting carrier sites. Aberrant or vital para-functions of AAC in basal uncoupling and in the mitochondrial pore transition were demonstrated in mitochondria and by patch clamp with reconstituted AAC. The first amino acid sequence of AAC and of any eukaryotic carrier furnished a 6-transmembrane helix folding model, and was the basis for mapping the structure by access studies with various probes, and for demonstrating the strong conformation changes demanded by the reorientation mechanism. Mutations served to elucidate the function of residues, including the particular sensitivity of ATP versus ADP transport to deletion of critical positive charge in AAC. After resisting for decades, at last the atomic crystal structure of the stabilised CAT-AAC complex emerged supporting the predicted principle fold of the AAC but showing unexpected features relevant to mechanism. Being a snapshot of an extreme abortive "c-state" the actual mechanism still remains a conjecture.
Collapse
|
43
|
Tadini-Buoninsegni F, Bartolommei G, Moncelli MR, Fendler K. Charge transfer in P-type ATPases investigated on planar membranes. Arch Biochem Biophys 2008; 476:75-86. [PMID: 18328799 DOI: 10.1016/j.abb.2008.02.031] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Revised: 02/19/2008] [Accepted: 02/20/2008] [Indexed: 11/18/2022]
Abstract
Planar lipid bilayers, e.g., black lipid membranes (BLM) and solid supported membranes (SSM), have been employed to investigate charge movements during the reaction cycle of P-type ATPases. The BLM/SSM method allows a direct measurement of the electrical currents generated by the cation transporter following chemical activation by a substrate concentration jump. The electrical current transients provides information about the reaction mechanism of the enzyme. In particular, the BLM/SSM technique allows identification of electrogenic steps which in turn may be used to localize ion translocation during the reaction cycle of the pump. In addition, using the high time resolution of the technique, especially when rapid activation via caged ATP is employed, rate constants of electrogenic and electroneutral steps can be determined. In the present review, we will discuss the main results obtained by the BLM and SSM methods and how they have contributed to unravel the transport mechanism of P-type ATPases.
Collapse
|
44
|
Ritter JB, Genzel Y, Reichl U. Simultaneous extraction of several metabolites of energy metabolism and related substances in mammalian cells: optimization using experimental design. Anal Biochem 2007; 373:349-69. [PMID: 18036549 DOI: 10.1016/j.ab.2007.10.037] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2007] [Revised: 10/13/2007] [Accepted: 10/24/2007] [Indexed: 10/22/2022]
Abstract
As a basis for the development of predictive mathematical models in systems biology and a quantitative understanding of cellular metabolism, reliable experimental data sets of intracellular metabolites are indispensable. A prerequisite for the acquisition of such data is the identification of a suitable sample preparation method. In this work, the extraction procedure for the simultaneous measurement of a wide range of intracellular metabolites from adherent mammalian cells in culture was optimized. A screening of several commonly used extraction protocols with Madin-Darby canine kidney (MDCK) cells found the methanol/chloroform (MeOH/CHCl(3)) and MeOH/Boil methods to be promising candidates for further analysis by anion-exchange chromatography. Both methods were optimized based on experimental design techniques with four response variables: Nucleotide Content, Energy Charge, Fructose 1,6-Bisphosphate content (F16bP), and Absorption at 280 nm. After data evaluation and with the help of desirability functions, an overall optimum for the extraction conditions was found. Using optimal settings, the extraction performances for MDCK and Vero cell cultivations of both methods were compared. Both methods extracted nearly the same absolute amounts of intracellular metabolites, suggesting that these methods are equal. However, recoveries for nucleotide diphosphates were significantly above 100% for both methods. This most likely was due to remaining nucleotide kinase activity during extraction. After combining individual steps of both methods, recoveries close to 100% for all metabolites could be reached. Absolute values of intracellular metabolites extracted with this modified method are comparable to the results of the two previously optimized methods, indicating a good extraction procedure according to the chosen response variables.
Collapse
Affiliation(s)
- Joachim B Ritter
- Max Planck Institute for Dynamics of Complex Technical Systems, 39106 Magdeburg, Germany.
| | | | | |
Collapse
|
45
|
Saks V, Kaambre T, Guzun R, Anmann T, Sikk P, Schlattner U, Wallimann T, Aliev M, Vendelin M. The creatine kinase phosphotransfer network: thermodynamic and kinetic considerations, the impact of the mitochondrial outer membrane and modelling approaches. Subcell Biochem 2007; 46:27-65. [PMID: 18652071 DOI: 10.1007/978-1-4020-6486-9_3] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In this review, we summarize the main structural and functional data on the role of the phosphocreatine (PCr)--creatine kinase (CK) pathway for compartmentalized energy transfer in cardiac cells. Mitochondrial creatine kinase, MtCK, fixed by cardiolipin molecules in the vicinity of the adenine nucleotide translocator, is a key enzyme in this pathway. Direct transfer of ATP and ADP between these proteins has been revealed both in experimental studies on the kinetics of the regulation of mitochondrial respiration and by mathematical modelling as a main mechanism of functional coupling of PCr production to oxidative phosphorylation. In cells in vivo or in permeabilized cells in situ, this coupling is reinforced by limited permeability of the outer membrane of the mitochondria for adenine nucleotides due to the contacts with cytoskeletal proteins. Due to these mechanisms, at least 80% of total energy is exported from mitochondria by PCr molecules. Mathematical modelling of intracellular diffusion and energy transfer shows that the main function of the PCr-CK pathway is to connect different pools (compartments) of ATP and, by this way, to overcome the local restrictions and diffusion limitation of adenine nucleotides due to the high degree of structural organization of cardiac cells.
Collapse
Affiliation(s)
- Valdur Saks
- Laboratory of Fundamental and Applied Bioenergetics, INSERM U 884, Joseph Fourier University, 2280, Rue de la Piscine, BP53X-38041, Grenoble Cedex 9, France
| | | | | | | | | | | | | | | | | |
Collapse
|
46
|
Nury H, Dahout-Gonzalez C, Trézéguet V, Lauquin GJM, Brandolin G, Pebay-Peyroula E. Relations between structure and function of the mitochondrial ADP/ATP carrier. Annu Rev Biochem 2007; 75:713-41. [PMID: 16451122 DOI: 10.1146/annurev.biochem.75.103004.142747] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Import and export of metabolites through mitochondrial membranes are vital processes that are highly controlled and regulated at the level of the inner membrane. Proteins of the mitochondrial carrier family ( MCF ) are embedded in this membrane, and each member of the family achieves the selective transport of a specific metabolite. Among these, the ADP/ATP carrier transports ADP into the mitochondrial matrix and exports ATP toward the cytosol after its synthesis. Because of its natural abundance, the ADP/ATP carrier is the best characterized within MCF, and a high-resolution structure of one conformation is known. The overall structure is basket shaped and formed by six transmembrane helices that are not only tilted with respect to the membrane, but three of them are also kinked at the level of prolines. The functional mechanisms, nucleotide recognition, and conformational changes for the transport, suggested from the structure, are discussed along with the large body of biochemical and functional results.
Collapse
Affiliation(s)
- H Nury
- Institut de Biologie Structurale Jean-Pierre Ebel, UMR 5075 CEA-CNRS-Université Joseph Fourier, F-38027 Grenoble cedex 1, France.
| | | | | | | | | | | |
Collapse
|
47
|
Kelety B, Diekert K, Tobien J, Watzke N, Dörner W, Obrdlik P, Fendler K. Transporter assays using solid supported membranes: a novel screening platform for drug discovery. Assay Drug Dev Technol 2006; 4:575-82. [PMID: 17115928 DOI: 10.1089/adt.2006.4.575] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Transporters are important targets in drug discovery. However, high throughput-capable assays for this class of membrane proteins are still missing. Here we present a novel drug discovery platform technology based on solid supported membranes. The functional principles of the technology are described, and a sample selection of transporter assays is discussed: the H(+)-dependent peptide transporter PepT1, the gastric proton pump, and the Na(+)/Ca(2+) exchanger. This technology promises to have an important impact on the drug discovery process.
Collapse
|
48
|
Zuber D, Krause R, Venturi M, Padan E, Bamberg E, Fendler K. Kinetics of charge translocation in the passive downhill uptake mode of the Na+/H+ antiporter NhaA of Escherichia coli. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2005; 1709:240-50. [PMID: 16139785 DOI: 10.1016/j.bbabio.2005.07.009] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2005] [Revised: 07/26/2005] [Accepted: 07/27/2005] [Indexed: 11/24/2022]
Abstract
The Na+/H+ antiporter NhaA is the main Na+ extrusion system in E. coli. Using direct current measurements combined with a solid supported membrane (SSM), we obtained electrical data of the function of NhaA purified and reconstituted in liposomes. These measurements demonstrate NhaA's electrogenicity, its specificity for Li+ and Na+ and its pronounced pH dependence in the range pH 6.5-8.5. The mutant G338S, in contrast, presents a pH independent profile, as reported previously. A complete right-side-out orientation of the NhaA antiporter within the proteoliposomal membrane was determined using a NhaA-specific antibody based ELISA assay. This allowed for the first time the investigation of NhaA in the passive downhill uptake mode corresponding to the transport of Na+ from the periplasmic to the cytoplasmic side of the membrane. In this mode, the transporter has kinetic properties differing significantly from those of the previously investigated efflux mode. The apparent Km values were 11 mM for Na+ and 7.3 mM for Li+ at basic pH and 180 mM for Na+ and 50 mM for Li+ at neutral pH. The data demonstrate that in the passive downhill uptake mode pH regulation of the carrier affects both apparent Km as well as turnover (Vmax).
Collapse
Affiliation(s)
- D Zuber
- Max Planck Institut für Biophysik, Max von Laue Strasse 3, D-60438 Frankfurt/Main, Germany
| | | | | | | | | | | |
Collapse
|
49
|
Flierl A, Chen Y, Coskun PE, Samulski RJ, Wallace DC. Adeno-associated virus-mediated gene transfer of the heart/muscle adenine nucleotide translocator (ANT) in mouse. Gene Ther 2005; 12:570-8. [PMID: 15647764 PMCID: PMC1456758 DOI: 10.1038/sj.gt.3302443] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Mitochondrial myopathy, associated with muscle weakness and progressive external ophthalmoplegia, is caused by mutations in mitochondria oxidative phosphorylation genes including the heart-muscle isoform of the mitochondrial adenine nucleotide translocator (ANT1). To develop therapies for mitochondrial disease, we have prepared a recombinant adeno-associated viral vector (rAAV) carrying the mouse Ant1 cDNA. This vector has been used to transduce muscle cells and muscle from Ant1 mutant mice, which manifest mitochondrial myopathy. AAV-ANT1 transduction resulted in long-term, stable expression of the Ant1 transgene in muscle precursor cells as well as differentiated muscle fibers. The transgene ANT1 protein was targeted to the mitochondrion, was inserted into the mitochondrial inner membrane, formed a functional ADP/ATP carrier, increased the mitochondrial export of ATP and reversed the histopathological changes associated with the mitochondrial myopathy. Thus, AAV transduction has the potential of providing symptomatic relief for the ophthalmoplegia and ptosis resulting from paralysis of the extraocular eye muscles cause by mutations in the Ant1 gene.
Collapse
Affiliation(s)
- A Flierl
- MAMMAG, University of California, Irvine, CA 92697-3940, USA
| | | | | | | | | |
Collapse
|
50
|
Gizatullina ZZ, Chen Y, Zierz S, Gellerich FN. Effects of extramitochondrial ADP on permeability transition of mouse liver mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2005; 1706:98-104. [PMID: 15620369 DOI: 10.1016/j.bbabio.2004.09.013] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2004] [Revised: 09/20/2004] [Accepted: 09/22/2004] [Indexed: 11/21/2022]
Abstract
Carboxyatractylate (CAT) and atractylate inhibit the mitochondrial adenine nucleotide translocator (ANT) and stimulate the opening of permeability transition pore (PTP). Following pretreatment of mouse liver mitochondria with 5 microM CAT and 75 microM Ca2+, the activity of PTP increased, but addition of 2 mM ADP inhibited the swelling of mitochondria. Extramitochondrial Ca2+ concentration measured with Calcium-Green 5N evidenced that 2 mM ADP did not remarkably decrease the free Ca2+ but the release of Ca2+ from loaded mitochondria was stopped effectively after addition of 2 mM ADP. CAT caused a remarkable decrease of the maximum amount of calcium ions, which can be accumulated by mitochondria. Addition of 2 mM ADP after 5 microM CAT did not change the respiration, but increased the mitochondrial capacity for Ca2+ at more than five times. Bongkrekic acid (BA) had a biphasic effect on PT. In the first minutes 5 microM BA increased the stability of mitochondrial membrane followed by a pronounced opening of PTP too. BA abolished the action about of 1 mM ADP, but was not able to induce swelling of mitochondria in the presence of 2 mM ADP. We conclude that the outer side of inner mitochondrial membrane has a low affinity sensor for ADP, modifying the activity of PTP. The pathophysiological importance of this process could be an endogenous prevention of PT at conditions of energetic depression.
Collapse
Affiliation(s)
- Zemfira Z Gizatullina
- Muskellabor der Neurologischen Klinik der Martin-Luther-Universität Halle-Wittenberg, Ernst-Grube-Str. 40, D-06097 Halle (Saale), Germany.
| | | | | | | |
Collapse
|