601
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Iwahashi A, Ishii A, Yamazaki N, Hashimoto M, Ohkura K, Kataoka M, Majima E, Terada H, Shinohara Y. Functionally important conserved length of C-terminal regions of yeast and bovine ADP/ATP carriers, identified by deletion mutants studies, and water accessibility of the amino acids at the C-terminal region of the yeast carrier. Mitochondrion 2008; 8:196-204. [DOI: 10.1016/j.mito.2008.01.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2007] [Revised: 01/09/2008] [Accepted: 01/28/2008] [Indexed: 10/22/2022]
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602
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Clémençon B, Rey M, Dianoux AC, Trézéguet V, Lauquin GJM, Brandolin G, Pelosi L. Structure-function relationships of the C-terminal end of the Saccharomyces cerevisiae ADP/ATP carrier isoform 2. J Biol Chem 2008; 283:11218-25. [PMID: 18299327 DOI: 10.1074/jbc.m709565200] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The adenine nucleotide carrier (Ancp) catalyzes the transport of ADP and ATP across the mitochondrial inner membrane, thus playing an essential role in the cellular energy metabolism. Two regions of Anc2p from Saccharomyces cerevisiae are specifically photolabeled using a photoactivable ADP derivative; they are the central matrix loop, m2, and the C-terminal end. To get more insights into the structure-function relationships of the C-terminal region during nucleotide transport, we have developed two independent approaches. In the first we have deleted the last eight amino acids of Anc2p (Anc2pDeltaCter) and demonstrated that the C-terminal end of Anc2p plays an essential role in yeast growth on a non-fermentable carbon source. This resulted from impaired nucleotide binding properties of the Anc2pDeltaCter variant in line with conversion of ADP binding sites from high to low affinity. In the second we probed the ligand-induced conformational changes of Anc2p C-terminal end (i) by assessing its accessibility to anti-C-terminal antibodies and (ii) by measuring intrinsic fluorescence changes of an Anc2p mutant containing only one tryptophan residue located at its C-terminal end (Anc2p3Y-u). We show that the C-terminal region is no further accessible to antibodies when Anc2p binds non-transportable analogues of ADP. Besides, Trp-316 fluorescence is highly increased upon ligand binding, suggesting large conformational changes. Taken together, our results highlight the involvement of the Anc2p C-terminal region in nucleotide recognition, binding, and transport.
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Affiliation(s)
- Benjamin Clémençon
- Laboratoire de Biochimie et Biophysique des Systè Intégrés, Institut de Recherches en Technologies et Sciences du Vivant, UMR 5092 CNRS-Commissariat à l'Energie Atomique-Université Joseph Fourier, F-38054 Grenoble cedex 9, France
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603
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Escribá PV, González-Ros JM, Goñi FM, Kinnunen PKJ, Vigh L, Sánchez-Magraner L, Fernández AM, Busquets X, Horváth I, Barceló-Coblijn G. Membranes: a meeting point for lipids, proteins and therapies. J Cell Mol Med 2008; 12:829-75. [PMID: 18266954 PMCID: PMC4401130 DOI: 10.1111/j.1582-4934.2008.00281.x] [Citation(s) in RCA: 276] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Membranes constitute a meeting point for lipids and proteins. Not only do they define the entity of cells and cytosolic organelles but they also display a wide variety of important functions previously ascribed to the activity of proteins alone. Indeed, lipids have commonly been considered a mere support for the transient or permanent association of membrane proteins, while acting as a selective cell/organelle barrier. However, mounting evidence demonstrates that lipids themselves regulate the location and activity of many membrane proteins, as well as defining membrane microdomains that serve as spatio-temporal platforms for interacting signalling proteins. Membrane lipids are crucial in the fission and fusion of lipid bilayers and they also act as sensors to control environmental or physiological conditions. Lipids and lipid structures participate directly as messengers or regulators of signal transduction. Moreover, their alteration has been associated with the development of numerous diseases. Proteins can interact with membranes through lipid co-/post-translational modifications, and electrostatic and hydrophobic interactions, van der Waals forces and hydrogen bonding are all involved in the associations among membrane proteins and lipids. The present study reviews these interactions from the molecular and biomedical point of view, and the effects of their modulation on the physiological activity of cells, the aetiology of human diseases and the design of clinical drugs. In fact, the influence of lipids on protein function is reflected in the possibility to use these molecular species as targets for therapies against cancer, obesity, neurodegenerative disorders, cardiovascular pathologies and other diseases, using a new approach called membrane-lipid therapy.
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Affiliation(s)
- Pablo V Escribá
- Laboratory of Molecular Cell Biomedicine, Dept of Biology-IUNICS, University of the Balearic Islands, Palma de Mallorca, Spain.
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604
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Leroch M, Neuhaus HE, Kirchberger S, Zimmermann S, Melzer M, Gerhold J, Tjaden J. Identification of a novel adenine nucleotide transporter in the endoplasmic reticulum of Arabidopsis. THE PLANT CELL 2008; 20:438-51. [PMID: 18296626 PMCID: PMC2276436 DOI: 10.1105/tpc.107.057554] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Many metabolic reactions in the endoplasmic reticulum (ER) require high levels of energy in the form of ATP, which is important for cell viability. Here, we report on an adenine nucleotide transporter residing in the ER membranes of Arabidopsis thaliana (ER-ANT1). Functional integration of ER-ANT1 in the cytoplasmic membrane of intact Escherichia coli cells reveals a high specificity for an ATP/ADP antiport. Immunodetection in transgenic ER-ANT1-C-MYC-tag Arabidopsis plants and immunogold labeling of wild-type pollen grain tissue using a peptide-specific antiserum reveal the localization of this carrier in ER membranes. Transgenic ER-ANT1-promoter-beta-glucuronidase Arabidopsis lines show high expression in ER-active tissues (i.e., pollen, seeds, root tips, apical meristems, or vascular bundles). Two independent ER-ANT1 Arabidopsis knockout lines indicate a high physiological relevance of ER-ANT1 for ATP transport into the plant ER (e.g., disruption of ER-ANT1 results in a drastic retardation of plant growth and impaired root and seed development). In these ER-ANT1 knockout lines, the expression levels of several genes encoding ER proteins that are dependent on a sufficient ATP supply (i.e., BiP [for luminal binding protein] chaperones, calreticulin chaperones, Ca2+-dependent protein kinase, and SEC61) are substantially decreased.
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Affiliation(s)
- Michaela Leroch
- Pflanzenphysiologie, Technische Universität Kaiserslautern, D-67663 Kaiserslautern, Germany
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605
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Williams BA, Haferkamp I, Keeling PJ. An ADP/ATP-Specific Mitochondrial Carrier Protein in the Microsporidian Antonospora locustae. J Mol Biol 2008; 375:1249-57. [DOI: 10.1016/j.jmb.2007.11.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2007] [Revised: 11/01/2007] [Accepted: 11/05/2007] [Indexed: 11/27/2022]
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606
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Geertsma ER, Nik Mahmood NAB, Schuurman-Wolters GK, Poolman B. Membrane reconstitution of ABC transporters and assays of translocator function. Nat Protoc 2008; 3:256-66. [DOI: 10.1038/nprot.2007.519] [Citation(s) in RCA: 196] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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607
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Schwarz M, Andrade-Navarro MA, Gross A. Mitochondrial carriers and pores: key regulators of the mitochondrial apoptotic program? Apoptosis 2008; 12:869-76. [PMID: 17453157 DOI: 10.1007/s10495-007-0748-2] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Mitochondria play a pivotal role in the process of apoptosis. Alterations in mitochondrial structure and function during apoptosis are regulated by proteins of the BCL-2 family, however their exact mechanism of action is largely unknown. Mitochondrial carriers and pores play an essential role in maintaining the normal function of mitochondria, and BCL-2 family members were shown to interact with several mitochondrial carriers/pores and to affect their function. This review focuses on the involvement of several of these mitochondrial carriers/pores in the regulation of the mitochondrial death pathway.
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Affiliation(s)
- Michal Schwarz
- Department of Biological Regulation, Weizmann Institute of Science, Rehovot 76100, Israel
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608
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Chapter 5 New Insights into the Mechanism of Precursor Protein Insertion into the Mitochondrial Membranes. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2008; 268:147-90. [DOI: 10.1016/s1937-6448(08)00805-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/10/2023]
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609
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Ivanova E, Jowitt TA, Lu H. Assembly of the Mitochondrial Tim9–Tim10 Complex: A Multi-step Reaction with Novel Intermediates. J Mol Biol 2008; 375:229-39. [DOI: 10.1016/j.jmb.2007.10.037] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2007] [Revised: 09/28/2007] [Accepted: 10/13/2007] [Indexed: 11/25/2022]
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610
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Alcock FH, Grossmann JG, Gentle IE, Likić VA, Lithgow T, Tokatlidis K. Conserved substrate binding by chaperones in the bacterial periplasm and the mitochondrial intermembrane space. Biochem J 2007; 409:377-87. [PMID: 17894549 DOI: 10.1042/bj20070877] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Mitochondria were derived from intracellular bacteria and the mitochondrial intermembrane space is topologically equivalent to the bacterial periplasm. Both compartments contain ATP-independent chaperones involved in the transport of hydrophobic membrane proteins. The mitochondrial TIM (translocase of the mitochondrial inner membrane) 10 complex and the periplasmic chaperone SurA were examined in terms of evolutionary relation, structural similarity, substrate binding specificity and their function in transporting polypeptides for insertion into membranes. The two chaperones are evolutionarily unrelated; structurally, they are also distinct both in their characteristics, as determined by SAXS (small-angle X-ray scattering), and in pairwise structural comparison using the distance matrix alignment (DALILite server). Despite their structural differences, SurA and the TIM10 complex share a common binding specificity in Pepscan assays of substrate proteins. Comprehensive analysis of the binding on a total of 1407 immobilized 13-mer peptides revealed that the TIM10 complex, like SurA, does not bind hydrophobic peptides generally, but that both chaperones display selectivity for peptides rich in aromatic residues and with net positive charge. This common binding specificity was not sufficient for SurA to completely replace TIM10 in yeast cells in vivo. In yeast cells lacking TIM10, when SurA is targeted to the intermembrane space of mitochondria, it binds translocating substrate proteins, but fails to completely transfer the substrate to the translocase in the mitochondrial inner membrane. We suggest that SurA was incapable of presenting substrates effectively to the primitive TOM (translocase of the mitochondrial outer membrane) and TIM complexes in early mitochondria, and was replaced by the more effective small Tim chaperone.
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Affiliation(s)
- Felicity H Alcock
- Institute of Molecular Biology and Biotechnology, Foundation of Research and Technology Hellas, PO Box 1385, 71110 Heraklion, Crete, Greece
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611
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Upadhyay AK, Wang J, Edmondson DE. Comparison of the Structural Properties of the Active Site Cavities of Human and Rat Monoamine Oxidase A and B in Their Soluble and Membrane-Bound Forms. Biochemistry 2007; 47:526-36. [DOI: 10.1021/bi7019707] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Anup K. Upadhyay
- Departments of Biochemistry and Chemistry, Emory University, Atlanta, Georgia 30322
| | - Jin Wang
- Departments of Biochemistry and Chemistry, Emory University, Atlanta, Georgia 30322
| | - Dale E. Edmondson
- Departments of Biochemistry and Chemistry, Emory University, Atlanta, Georgia 30322
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612
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Schlame M. Cardiolipin synthesis for the assembly of bacterial and mitochondrial membranes. J Lipid Res 2007; 49:1607-20. [PMID: 18077827 DOI: 10.1194/jlr.r700018-jlr200] [Citation(s) in RCA: 292] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
In this article, the formation of prokaryotic and eukaryotic cardiolipin is reviewed in light of its biological function. I begin with a detailed account of the structure of cardiolipin, its stereochemistry, and the resulting physical properties, and I present structural analogs of cardiolipin that occur in some organisms. Then I continue to discuss i) the de novo formation of cardiolipin, ii) its acyl remodeling, iii) the assembly of cardiolipin into biological membranes, and iv) the degradation of cardiolipin, which may be involved in apoptosis and mitochondrial fusion. Thus, this article covers the entire metabolic cycle of this unique phospholipid. It is shown that mitochondria produce cardiolipin species with a high degree of structural uniformity and molecular symmetry, among which there is often a dominant form with four identical acyl chains. The subsequent assembly of cardiolipin into functional membranes is largely unknown, but the analysis of crystal structures of membrane proteins has revealed a first glimpse into the underlying principles of cardiolipin-protein interactions. Disturbances of cardiolipin metabolism are crucial in the pathophysiology of human Barth syndrome and perhaps also play a role in diabetes and ischemic heart disease.
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Affiliation(s)
- Michael Schlame
- Department of Anesthesiology and Cell Biology, New York University School of Medicine, New York, NY 10016, USA.
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613
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Abstract
In fungal cells, transcriptional regulatory mechanisms play a central role in both the homeostatic regulation of the essential metals iron, copper and zinc and in the detoxification of heavy metal ions such as cadmium. Fungi detect changes in metal ion levels using unique metallo-regulatory factors whose activity is responsive to the cellular metal ion status. New studies have revealed that these factors not only regulate the expression of genes required for metal ion acquisition, storage or detoxification but also globally remodel metabolism to conserve metal ions or protect against metal toxicity. This review focuses on the mechanisms metallo-regulators use to up- and down-regulate gene expression.
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Affiliation(s)
- Amanda J Bird
- Division of Hematology, Department of Internal Medicine, University of Utah Health Sciences Center, Salt Lake City, UT 84132, USA
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614
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Zara V, Ferramosca A, Capobianco L, Baltz KM, Randel O, Rassow J, Palmieri F, Papatheodorou P. Biogenesis of yeast dicarboxylate carrier: the carrier signature facilitates translocation across the mitochondrial outer membrane. J Cell Sci 2007; 120:4099-106. [DOI: 10.1242/jcs.018929] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A family of related carrier proteins mediates the exchange of metabolites across the mitochondrial inner membrane. The carrier signature Px[D/E]xx[K/R] is a highly conserved sequence motif in all members of this family. To determine its function in the biogenesis of carrier proteins, we used the dicarboxylate carrier (DIC) of yeast as a model protein. We found that the carrier signature was dispensable in binding of the newly synthesized protein to the import receptor Tom70, but that it was specifically required for efficient translocation across the mitochondrial outer membrane. To determine the relevance of individual amino acid residues of the carrier signature in the transport activity of the protein, we exchanged defined residues with alanine and reconstituted the mutant proteins in vitro. Substitution of the carrier signature in helix H1 reduced the transport activity for [33P]-phosphate by approximately 90% and an additional substitution of the carrier signature in helix H5 blocked the transport activity completely. We conclude that the carrier signature of the dicarboxylate carrier is involved both in the biogenesis and in the transport activity of the functional protein.
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Affiliation(s)
- Vincenzo Zara
- Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Università del Salento, Via Provinciale Lecce-Monteroni, I-73100 Lecce, Italy
| | - Alessandra Ferramosca
- Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Università del Salento, Via Provinciale Lecce-Monteroni, I-73100 Lecce, Italy
| | - Loredana Capobianco
- Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Università del Salento, Via Provinciale Lecce-Monteroni, I-73100 Lecce, Italy
- Dipartimento Farmaco-Biologico, Università di Bari, I-70125 Bari, Italy
| | - Katrin M. Baltz
- Institut für Physiologische Chemie, Medizinische Fakultät der Ruhr-Universität Bochum, D-44780 Bochum, Germany
| | - Olga Randel
- Institut für Physiologische Chemie, Medizinische Fakultät der Ruhr-Universität Bochum, D-44780 Bochum, Germany
| | - Joachim Rassow
- Institut für Physiologische Chemie, Medizinische Fakultät der Ruhr-Universität Bochum, D-44780 Bochum, Germany
| | | | - Panagiotis Papatheodorou
- Institut für Physiologische Chemie, Medizinische Fakultät der Ruhr-Universität Bochum, D-44780 Bochum, Germany
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615
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Phosphatidic acid plays a special role in stabilizing and folding of the tetrameric potassium channel KcsA. FEBS Lett 2007; 581:5715-22. [DOI: 10.1016/j.febslet.2007.11.039] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2007] [Revised: 11/09/2007] [Accepted: 11/13/2007] [Indexed: 11/22/2022]
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616
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Conformation-dependent accessibility of Cys-136 and Cys-155 of the mitochondrial rat carnitine/acylcarnitine carrier to membrane-impermeable SH reagents. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2007; 1767:1331-9. [DOI: 10.1016/j.bbabio.2007.08.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2007] [Revised: 08/29/2007] [Accepted: 08/30/2007] [Indexed: 11/23/2022]
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617
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Kihira Y, Hashimoto M, Shinohara Y, Majima E, Terada H. Roles of adjoining Asp and Cys residues of first matrix-facing loop in transport activity of yeast and bovine mitochondrial ADP/ATP carriers. J Biochem 2007; 139:575-82. [PMID: 16567423 DOI: 10.1093/jb/mvj052] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The mitochondrial ADP/ATP carrier (AAC) transports substrate by interconversion of its conformation between m- and c-states. The 1st loop facing the matrix (LM1) is extruded into the matrix in the m-state and is suggested to intrude into the mitochondrial membrane on conversion to the c-state conformation [Hashimoto, M., Majima, E., Goto, S., Shinohara, Y., and Terada, H. (1999) Biochemistry 38, 1050-1056]. To elucidate the mechanism of the translocation of LM1, we examined the effects of site-directed mutagenesis of two adjoining residues, Cys56 and Asp55 in the bovine type 1 AAC and Cys73 and Asp72 in the yeast type 2 AAC, on the substrate transport activity. We found that (i) replacement of the Cys by bulky and hydrophilic residues was unfavorable for efficient transport activity, (ii) the carboxyl groups of the Asp residues of the bovine and yeast AACs were essential and strictly position-specific, and (iii) hence, the mutation to Glu showed transport activity comparable to that of the native AACs. Based on these results, we discussed the functional role of LM1 in the transport activity of AAC.
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Affiliation(s)
- Yoshitaka Kihira
- Faculty of Pharmaceutical Sciences, University of Toyama, 2630, Sugitani, Toyama 930-0194
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618
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Inhibition of the adenine nucleotide translocator by N-acetyl perfluorooctane sulfonamides in vitro. Toxicol Appl Pharmacol 2007; 227:184-95. [PMID: 18048072 DOI: 10.1016/j.taap.2007.10.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2007] [Revised: 10/15/2007] [Accepted: 10/17/2007] [Indexed: 11/21/2022]
Abstract
N-alkyl perfluorooctane sulfonamides have been widely used as surfactants on fabrics and papers, fire retardants, and anti-corrosion agents, among many other commercial applications. The global distribution and environmental persistence of these compounds has generated considerable interest regarding potential toxic effects. We have previously reported that perfluorooctanesulfonamidoacetate (FOSAA) and N-ethylperfluorooctanesulfonamidoacetate (N-EtFOSAA) induce the mitochondrial permeability transition (MPT) in vitro. In this study we tested the hypothesis that FOSAA and N-EtFOSAA interact with the adenine nucleotide translocator (ANT) resulting in a functional inhibition of the translocator and induction of the MPT. Respiration and membrane potential of freshly isolated liver mitochondria from Sprague-Dawley rats were measured using an oxygen electrode and a tetraphenylphosphonium-selective (TPP(+)) electrode, respectively. Mitochondrial swelling was measured spectrophotometrically. The ANT ligands bongkregkic acid (BKA) and carboxyatractyloside (cATR) inhibited uncoupling of mitochondrial respiration caused by 10 microM N-EtFOSAA, 40 microM FOSAA, and the positive control 8 microM oleic acid. ADP-stimulated respiration and depolarization of mitochondrial membrane potential were inhibited by cATR, FOSAA, N-EtFOSAA, and oleic acid, but not by FCCP. BKA inhibited calcium-dependent mitochondrial swelling induced by FOSAA, N-EtFOSAA, and oleic acid. Seventy-five micromolar ADP also inhibited swelling induced by the test compounds, but cATR induced swelling was not inhibited by ADP. Results of this investigation indicate that N-acetyl perfluorooctane sulfonamides interact directly with the ANT to inhibit ADP translocation and induce the MPT, one or both of which may account for the metabolic dysfunction observed in vivo.
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619
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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.
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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
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620
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Roy A, Roberts FG, Wilderman PR, Zhou K, Peters RJ, Coates RM. 16-Aza-ent-beyerane and 16-Aza-ent-trachylobane: potent mechanism-based inhibitors of recombinant ent-kaurene synthase from Arabidopsis thaliana. J Am Chem Soc 2007; 129:12453-60. [PMID: 17892288 PMCID: PMC3714097 DOI: 10.1021/ja072447e] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The secondary ent-beyeran-16-yl carbocation (7) is a key branch point intermediate in mechanistic schemes to rationalize the cyclic structures of many tetra- and pentacyclic diterpenes, including ent-beyerene, ent-kaurene, ent-trachylobane, and ent-atiserene, presumed precursors to >1000 known diterpenes. To evaluate these mechanistic hypotheses, we synthesized the heterocyclic analogues 16-aza-ent-beyerane (12) and 16-aza-ent-trachylobane (13) by means of Hg(II)- and Pb(IV)-induced cyclizations onto the Delta12 double bonds of tricyclic intermediates bearing carbamoylmethyl and aminomethyl groups at C-8. The 13,16-seco-16-norcarbamate (20a) was obtained from ent-beyeran-16-one oxime (17) by Beckmann fragmentation, hydrolysis, and Curtius rearrangement. The aza analogues inhibited recombinant ent-kaurene synthase from Arabidopsis thaliana (GST-rAtKS) with inhibition constants (IC50 = 1 x 10-7 and 1 x 10-6 M) similar in magnitude to the pseudo-binding constant of the bicyclic ent-copalyl diphosphate substrate (Km = 3 x 10-7 M). Large enhancements of binding affinities (IC50 = 4 x 10-9 and 2 x 10-8 M) were observed in the presence of 1 mM pyrophosphate, which is consistent with a tightly bound ent-beyeranyl+/pyrophosphate- ion pair intermediate in the cyclization-rearrangement catalyzed by this diterpene synthase. The weak inhibition (IC50 = 1 x 10-5 M) exhibited by ent-beyeran-16-exo-yl diphosphate (11) and its failure to undergo bridge rearrangement to kaurene appear to rule out the covalent diphosphate as a free intermediate. 16-Aza-ent-beyerane is proposed as an effective mimic for the ent-beyeran-16-yl carbocation with potential applications as an active site probe for the various ent-diterpene cyclases and as a novel, selective inhibitor of gibberellin biosynthesis in plants.
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Affiliation(s)
- Arnab Roy
- Albany Molecular Sciences, Hyderabad, India
- Department of Chemistry University of Illinois, 600 South Mathews Avenue Urbana, IL 61801
| | - Frank G. Roberts
- Department of Chemistry, University of Chicago, Chicago, IL
- Department of Chemistry University of Illinois, 600 South Mathews Avenue Urbana, IL 61801
| | - P. Ross Wilderman
- Department of Biochemistry, Biophysics, & Molecular Biology, Iowa State University, Ames, IA 50011
| | - Ke Zhou
- Department of Biochemistry, Biophysics, & Molecular Biology, Iowa State University, Ames, IA 50011
| | - Reuben J. Peters
- Department of Biochemistry, Biophysics, & Molecular Biology, Iowa State University, Ames, IA 50011
| | - Robert M. Coates
- Department of Chemistry University of Illinois, 600 South Mathews Avenue Urbana, IL 61801
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621
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Abstract
About 10% to 15% of the nuclear genes of eukaryotic organisms encode mitochondrial proteins. These proteins are synthesized in the cytosol and recognized by receptors on the surface of mitochondria. Translocases in the outer and inner membrane of mitochondria mediate the import and intramitochondrial sorting of these proteins; ATP and the membrane potential are used as energy sources. Chaperones and auxiliary factors assist in the folding and assembly of mitochondrial proteins into their native, three-dimensional structures. This review summarizes the present knowledge on the import and sorting of mitochondrial precursor proteins, with a special emphasis on unresolved questions and topics of current research.
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Affiliation(s)
- Walter Neupert
- Institut für Physiologische Chemie, Universität München, 81377 München, Germany.
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622
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Carroll J, Altman MC, Fearnley IM, Walker JE. Identification of membrane proteins by tandem mass spectrometry of protein ions. Proc Natl Acad Sci U S A 2007; 104:14330-5. [PMID: 17720804 PMCID: PMC1952138 DOI: 10.1073/pnas.0706817104] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The most common way of identifying proteins in proteomic analyses is to use short segments of sequence ("tags") determined by mass spectrometric analysis of proteolytic fragments. The approach is effective with globular proteins and with membrane proteins with significant polar segments between membrane-spanning alpha-helices, but it is ineffective with other hydrophobic proteins where protease cleavage sites are either infrequent or absent. By developing methods to purify hydrophobic proteins in organic solvents and by fragmenting ions of these proteins by collision induced dissociation with argon, we have shown that partial sequences of many membrane proteins can be deduced easily by manual inspection. The spectra from small proteolipids (1-4 transmembrane alpha-helices) are dominated usually by fragment ions arising from internal amide cleavages, from which internal sequences can be obtained, whereas the spectra from larger membrane proteins (5-18 transmembrane alpha-helices) often contain fragment ions from N- and/or C-terminal parts yielding sequences in those regions. With these techniques, we have, for example, identified an abundant protein of unknown function from inner membranes of mitochondria that to our knowledge has escaped detection in proteomic studies, and we have produced sequences from 10 of 13 proteins encoded in mitochondrial DNA. They include the ND6 subunit of complex I, the last of its 45 subunits to be analyzed. The procedures have the potential to be developed further, for example by using newly introduced methods for protein ion dissociation to induce fragmentation of internal regions of large membrane proteins, which may remain partially folded in the gas phase.
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Affiliation(s)
- Joe Carroll
- Medical Research Council Dunn Human Nutrition Unit, Hills Road, Cambridge CB2 0XY, United Kingdom
| | - Matthew C. Altman
- Medical Research Council Dunn Human Nutrition Unit, Hills Road, Cambridge CB2 0XY, United Kingdom
| | - Ian M. Fearnley
- Medical Research Council Dunn Human Nutrition Unit, Hills Road, Cambridge CB2 0XY, United Kingdom
| | - John E. Walker
- Medical Research Council Dunn Human Nutrition Unit, Hills Road, Cambridge CB2 0XY, United Kingdom
- *To whom correspondence should be addressed. E-mail:
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623
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Bhangoo MK, Tzankov S, Fan AC, Dejgaard K, Thomas DY, Young JC. Multiple 40-kDa heat-shock protein chaperones function in Tom70-dependent mitochondrial import. Mol Biol Cell 2007; 18:3414-28. [PMID: 17596514 PMCID: PMC1951752 DOI: 10.1091/mbc.e07-01-0088] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Mitochondrial preproteins that are imported via the translocase of the mitochondrial outer membrane (Tom)70 receptor are complexed with cytosolic chaperones before targeting to the mitochondrial outer membrane. The adenine nucleotide transporter (ANT) follows this pathway, and its purified mature form is identical to the preprotein. Purified ANT was reconstituted with chaperones in reticulocyte lysate, and bound proteins were identified by mass spectrometry. In addition to 70-kDa heat-shock cognate protein (Hsc70) and 90-kDa heat-shock protein (Hsp90), a specific subset of cochaperones were found, but no mitochondria-specific targeting factors were found. Interestingly, three different Hsp40-related J-domain proteins were identified: DJA1, DJA2, and DJA4. The DJAs bound preproteins to different extents through their C-terminal regions. DJA dominant-negative mutants lacking the N-terminal J-domains impaired mitochondrial import. The mutants blocked the binding of Hsc70 to preprotein, but with varying efficiency. The DJAs also showed significant differences in activation of the Hsc70 ATPase and Hsc70-dependent protein refolding. In HeLa cells, the DJAs increased new protein folding and mitochondrial import, although to different extents. No single DJA was superior to the others in all aspects, but each had a profile of partial specialization. The Hsp90 cochaperones p23 and Aha1 also regulated Hsp90-preprotein interactions. We suggest that multiple cochaperones with similar yet partially specialized properties cooperate in optimal chaperone-preprotein complexes.
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Affiliation(s)
- Melanie K. Bhangoo
- Department of Biochemistry, McGill University, Montreal, QC, H3G 1Y6, Canada
| | - Stefan Tzankov
- Department of Biochemistry, McGill University, Montreal, QC, H3G 1Y6, Canada
| | - Anna C.Y. Fan
- Department of Biochemistry, McGill University, Montreal, QC, H3G 1Y6, Canada
| | - Kurt Dejgaard
- Department of Biochemistry, McGill University, Montreal, QC, H3G 1Y6, Canada
| | - David Y. Thomas
- Department of Biochemistry, McGill University, Montreal, QC, H3G 1Y6, Canada
| | - Jason C. Young
- Department of Biochemistry, McGill University, Montreal, QC, H3G 1Y6, Canada
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624
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Floyd S, Favre C, Lasorsa FM, Leahy M, Trigiante G, Stroebel P, Marx A, Loughran G, O'Callaghan K, Marobbio CM, Slotboom DJ, Kunji ER, Palmieri F, O'Connor R. The insulin-like growth factor-I-mTOR signaling pathway induces the mitochondrial pyrimidine nucleotide carrier to promote cell growth. Mol Biol Cell 2007; 18:3545-55. [PMID: 17596519 PMCID: PMC1951771 DOI: 10.1091/mbc.e06-12-1109] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The insulin/insulin-like growth factor (IGF) signaling pathway to mTOR is essential for the survival and growth of normal cells and also contributes to the genesis and progression of cancer. This signaling pathway is linked with regulation of mitochondrial function, but how is incompletely understood. Here we show that IGF-I and insulin induce rapid transcription of the mitochondrial pyrimidine nucleotide carrier PNC1, which shares significant identity with the essential yeast mitochondrial carrier Rim2p. PNC1 expression is dependent on PI-3 kinase and mTOR activity and is higher in transformed fibroblasts, cancer cell lines, and primary prostate cancers than in normal tissues. Overexpression of PNC1 enhances cell size, whereas suppression of PNC1 expression causes reduced cell size and retarded cell cycle progression and proliferation. Cells with reduced PNC1 expression have reduced mitochondrial UTP levels, but while mitochondrial membrane potential and cellular ATP are not altered, cellular ROS levels are increased. Overall the data indicate that PNC1 is a target of the IGF-I/mTOR pathway that is essential for mitochondrial activity in regulating cell growth and proliferation.
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Affiliation(s)
- Suzanne Floyd
- *Cell Biology Laboratory, Department of Biochemistry, BioSciences Institute, National University of Ireland, Cork, Ireland
| | - Cedric Favre
- *Cell Biology Laboratory, Department of Biochemistry, BioSciences Institute, National University of Ireland, Cork, Ireland
| | - Francesco M. Lasorsa
- Department of Pharmaco-Biology, Laboratory of Biochemistry and Molecular Biology, University of Bari, and Consiglio Nazionale delle Ricerche Institute of Biomembranes and Bioenergetics, 70125 Bari, Italy
| | - Madeline Leahy
- *Cell Biology Laboratory, Department of Biochemistry, BioSciences Institute, National University of Ireland, Cork, Ireland
| | - Giuseppe Trigiante
- *Cell Biology Laboratory, Department of Biochemistry, BioSciences Institute, National University of Ireland, Cork, Ireland
| | - Philipp Stroebel
- Institute of Pathology, University Hospital Mannheim, University of Heidelberg, D68135 Mannheim, Germany; and
| | - Alexander Marx
- Institute of Pathology, University Hospital Mannheim, University of Heidelberg, D68135 Mannheim, Germany; and
| | - Gary Loughran
- *Cell Biology Laboratory, Department of Biochemistry, BioSciences Institute, National University of Ireland, Cork, Ireland
| | - Katie O'Callaghan
- *Cell Biology Laboratory, Department of Biochemistry, BioSciences Institute, National University of Ireland, Cork, Ireland
| | - Carlo M.T. Marobbio
- Department of Pharmaco-Biology, Laboratory of Biochemistry and Molecular Biology, University of Bari, and Consiglio Nazionale delle Ricerche Institute of Biomembranes and Bioenergetics, 70125 Bari, Italy
| | - Dirk J. Slotboom
- Medical Research Council, Dunn Human Nutrition Unit, Cambridge CB2 2XY, United Kingdom
| | - Edmund R.S. Kunji
- Medical Research Council, Dunn Human Nutrition Unit, Cambridge CB2 2XY, United Kingdom
| | - Ferdinando Palmieri
- Department of Pharmaco-Biology, Laboratory of Biochemistry and Molecular Biology, University of Bari, and Consiglio Nazionale delle Ricerche Institute of Biomembranes and Bioenergetics, 70125 Bari, Italy
| | - Rosemary O'Connor
- *Cell Biology Laboratory, Department of Biochemistry, BioSciences Institute, National University of Ireland, Cork, Ireland
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625
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Bamber L, Harding M, Monné M, Slotboom DJ, Kunji ERS. The yeast mitochondrial ADP/ATP carrier functions as a monomer in mitochondrial membranes. Proc Natl Acad Sci U S A 2007; 104:10830-4. [PMID: 17566106 PMCID: PMC1891095 DOI: 10.1073/pnas.0703969104] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2007] [Indexed: 11/18/2022] Open
Abstract
Mitochondrial carriers are believed widely to be dimers both in structure and function. However, the structural fold is a barrel of six transmembrane alpha-helices without an obvious dimerisation interface. Here, we show by negative dominance studies that the yeast mitochondrial ADP/ATP carrier 2 from Saccharomyces cerevisiae (AAC2) is functional as a monomer in the mitochondrial membrane. Adenine nucleotide transport by wild-type AAC2 is inhibited by the sulfhydryl reagent 2-sulfonatoethyl-methanethiosulfonate (MTSES), whereas the activity of a mutant AAC2, devoid of cysteines, is unaffected. Wild-type and cysteine-less AAC2 were coexpressed in different molar ratios in yeast mitochondrial membranes. After addition of MTSES the residual transport activity correlated linearly with the fraction of cysteine-less carrier present in the membranes, and so the two versions functioned independently of each other. Also, the cysteine-less and wild-type carriers were purified separately, mixed in defined ratios and reconstituted into liposomes. Again, the residual transport activity in the presence of MTSES depended linearly on the amount of cysteine-less carrier. Thus, the entire transport cycle for ADP/ATP exchange is carried out by the monomer.
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Affiliation(s)
- Lisa Bamber
- Medical Research Council, Dunn Human Nutrition Unit, Hills Road, Cambridge CB2 2XY, United Kingdom
| | - Marilyn Harding
- Medical Research Council, Dunn Human Nutrition Unit, Hills Road, Cambridge CB2 2XY, United Kingdom
| | - Magnus Monné
- Medical Research Council, Dunn Human Nutrition Unit, Hills Road, Cambridge CB2 2XY, United Kingdom
| | - Dirk-Jan Slotboom
- Medical Research Council, Dunn Human Nutrition Unit, Hills Road, Cambridge CB2 2XY, United Kingdom
| | - Edmund R. S. Kunji
- Medical Research Council, Dunn Human Nutrition Unit, Hills Road, Cambridge CB2 2XY, United Kingdom
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626
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Buzhynskyy N, Sens P, Prima V, Sturgis JN, Scheuring S. Rows of ATP synthase dimers in native mitochondrial inner membranes. Biophys J 2007; 93:2870-6. [PMID: 17557793 PMCID: PMC1989723 DOI: 10.1529/biophysj.107.109728] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The ATP synthase is a nanometric rotary machine that uses a transmembrane electrochemical gradient to form ATP. The structures of most components of the ATP synthase are known, and their organization has been elucidated. However, the supramolecular assembly of ATP synthases in biological membranes remains unknown. Here we show with submolecular resolution the organization of ATP synthases in the yeast mitochondrial inner membranes. The atomic force microscopy images we have obtained show how these molecules form dimers with characteristic 15 nm distance between the axes of their rotors through stereospecific interactions of the membrane embedded portions of their stators. A different interaction surface is responsible for the formation of rows of dimers. Such an organization elucidates the role of the ATP synthase in mitochondrial morphology. Some dimers have a different morphology with 10 nm stalk-to-stalk distance, in line with ATP synthases that are accessible to IF1 inhibition. Rotation torque compensation within ATP synthase dimers stabilizes the ATP synthase structure, in particular the stator-rotor interaction.
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627
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Bamber L, Slotboom DJ, Kunji ERS. Yeast mitochondrial ADP/ATP carriers are monomeric in detergents as demonstrated by differential affinity purification. J Mol Biol 2007; 371:388-95. [PMID: 17572439 DOI: 10.1016/j.jmb.2007.05.072] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2007] [Revised: 05/23/2007] [Accepted: 05/24/2007] [Indexed: 10/23/2022]
Abstract
Most mitochondrial carriers carry out equimolar exchange of substrates and they are believed widely to exist as homo-dimers. Here we show by differential tagging that the yeast mitochondrial ADP/ATP carrier AAC2 is a monomer in mild detergents. Carriers with and without six-histidine or hemagglutinin tags were co-expressed in defined molar ratios in yeast mitochondrial membranes. Their specific transport activity was unaffected by tagging or by co-expression. The co-expressed carriers were extracted from the membranes with mild detergents and purified rapidly by affinity chromatography. All of the untagged carriers were in the flow-through of the affinity column, whereas all of the tagged carriers bound to the column and were eluted subsequently, showing that stable dimers, consisting of associated tagged and untagged carriers, were not present. The specific inhibitors carboxyatractyloside and bongkrekic acid and the substrates ADP, ATP and ADP plus ATP were added during the experiments to determine whether lack of association might have been caused by carriers being prevented from cycling through the various states in the transport cycle where dimers might form. All of the protein was accounted for, but stable dimers were not detected in any of these conditions, showing that yeast ADP/ATP carriers are monomeric in detergents in agreement with their hydrodynamic properties and with their structure. Since strong interactions between monomers were not observed in any part of the transport cycle, it is highly unlikely that the carriers function cooperatively. Therefore, transport mechanisms need to be considered in which the carrier is operational as a monomer.
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Affiliation(s)
- Lisa Bamber
- The Medical Research Council, Dunn Human Nutrition Unit, Hills Road, CB2 2XY, Cambridge, UK
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628
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Schuldiner S. When biochemistry meets structural biology: the cautionary tale of EmrE. Trends Biochem Sci 2007; 32:252-8. [PMID: 17452106 DOI: 10.1016/j.tibs.2007.04.002] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2007] [Revised: 03/19/2007] [Accepted: 04/13/2007] [Indexed: 11/23/2022]
Abstract
When biochemistry meets structural biology a more complete understanding of the mechanism of biological macromolecules is usually achieved. Several high-resolution structures of ion-coupled transporters have enriched the understanding of mechanisms of substrate recognition, translocation and coupling of substrate fluxes. However, two X-ray structures of EmrE, the smallest ion-coupled multi-drug transporter, raised questions over the veracity of the structural model and represented a cautionary tale about the difficulty of determining the 3D structures of membrane proteins and the dangers of ignoring biochemical results. The 3D structures of EmrE have since been retracted because of faulty software, but the suggestion that the protomers in the dimer are in an antiparallel topological orientation sparked controversy that is still ongoing.
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Affiliation(s)
- Shimon Schuldiner
- Department of Biological Chemistry, Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
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629
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Lacapère JJ, Pebay-Peyroula E, Neumann JM, Etchebest C. Determining membrane protein structures: still a challenge! Trends Biochem Sci 2007; 32:259-70. [PMID: 17481903 DOI: 10.1016/j.tibs.2007.04.001] [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] [Received: 12/14/2006] [Revised: 03/07/2007] [Accepted: 04/13/2007] [Indexed: 11/20/2022]
Abstract
Determination of structures and dynamics events of transmembrane proteins is important for the understanding of their function. Analysis of such events requires high-resolution 3D structures of the different conformations coupled with molecular dynamics analyses describing the conformational pathways. However, the solution of 3D structures of transmembrane proteins at atomic level remains a particular challenge for structural biochemists--the need for purified and functional transmembrane proteins causes a 'bottleneck'. There are various ways to obtain 3D structures: X-ray diffraction, electron microscopy, NMR and modelling; these methods are not used exclusively of each other, and the chosen combination depends on several criteria. Progress in this field will improve knowledge of ligand-induced activation and inhibition of membrane proteins in addition to aiding the design of membrane-protein-targeted drugs.
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Affiliation(s)
- Jean-Jacques Lacapère
- INSERM, U773, Centre de Recherche Biomédicale Bichat Beaujon CRB3, Faculté de Médecine X. Bichat, Université Paris 7, BP 416, F-75018, Paris, France.
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630
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Lee JH, Harvat EM, Stevens JM, Ferguson SJ, Saier MH. Evolutionary origins of members of a superfamily of integral membrane cytochrome c biogenesis proteins. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:2164-81. [PMID: 17706591 DOI: 10.1016/j.bbamem.2007.04.022] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2006] [Revised: 03/22/2007] [Accepted: 04/24/2007] [Indexed: 11/20/2022]
Abstract
We have analyzed the relationships of homologues of the Escherichia coli CcmC protein for probable topological features and evolutionary relationships. We present bioinformatic evidence suggesting that the integral membrane proteins CcmC (E. coli; cytochrome c biogenesis System I), CcmF (E. coli; cytochrome c biogenesis System I) and ResC (Bacillus subtilis; cytochrome c biogenesis System II) are all related. Though the molecular functions of these proteins have not been fully described, they appear to be involved in the provision of heme to c-type cytochromes, and so we have named them the putative Heme Handling Protein (HHP) family (TC #9.B.14). Members of this family exhibit 6, 8, 10, 11, 13 or 15 putative transmembrane segments (TMSs). We show that intragenic triplication of a 2 TMS element gave rise to a protein with a 6 TMS topology, exemplified by CcmC. This basic 6 TMS unit then gave rise to two distinct types of proteins with 8 TMSs, exemplified by ResC and the archaeal CcmC, and these further underwent fusional or insertional events yielding proteins with 10, 11 and 13 TMSs (ResC homologues) as well as 15 TMSs (CcmF homologues). Specific evolutionary pathways taken are proposed. This work provides the first evidence for the pathway of appearance of distantly related proteins required for post-translational maturation of c-type cytochromes in bacteria, plants, protozoans and archaea.
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Affiliation(s)
- Jong-Hoon Lee
- Division of Biological Sciences, University of California at San Diego, La Jolla, CA 92093-0116, USA
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631
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Heptakis(6-deoxy-6-guanidino)-β-cyclodextrin: an artificial model for mitochondrial ADP/ATP carrier. Tetrahedron Lett 2007. [DOI: 10.1016/j.tetlet.2007.03.096] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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632
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Aliverdieva DA, Mamaev DV, Bondarenko DI, Sholtz KF. Topography of the active site of the Saccharomyces cerevisiae plasmalemmal dicarboxylate transporter studied using lipophilic derivatives of its substrates. BIOCHEMISTRY (MOSCOW) 2007; 72:264-74. [PMID: 17447879 DOI: 10.1134/s0006297907030030] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
2-Alkylmalonates and O-acyl-L-malates have been found to competitively inhibit the dicarboxylate transporter of Saccharomyces cerevisiae cells, and the substrate derivatives chosen did not penetrate across the plasmalemma under the experiment conditions. Probing of the active site of this transporter has revealed a large lipophilic area stretching between the 0.72 to 2.5 nm from the substrate-binding site. Itaconate inhibited the transport fivefold more effectively than L-malate. This suggests the existence of a hydrophobic region immediately near the dicarboxylate-binding site (to 0.72 nm). The yeast plasmalemmal transporter was different from the rat liver mitochondrial dicarboxylate transporter. An area with variable lipophilicity adjoining the substrate-binding site has been revealed in the latter by a similar method. This area is mainly hydrophobic at distances up to 1.76 nm from the binding site and is separated by a hydrophilic region from 0.38 to 0.88 nm. Fumarate but not maleate competitively inhibited succinate transport into the S. cerevisiae cells. It is suggested that the plasmalemmal transporter binds the substrate in the trans-conformation. The prospects of the proposed approach for scanning lipophilic profiles of channels of different transporters are discussed.
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Affiliation(s)
- D A Aliverdieva
- Caspian Institute of Biological Resources, Dagestan Research Center, Russian Academy of Sciences, Makhachkala, Russia
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633
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Perchiniak E, Lawrence SA, Kasten S, Woodard BA, Taylor SM, Moran RG. Probing the mechanism of the hamster mitochondrial folate transporter by mutagenesis and homology modeling. Biochemistry 2007; 46:1557-67. [PMID: 17279620 DOI: 10.1021/bi062191+] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The mitochondrial folate transporter (MFT) was previously identified in human and hamster cells. Sequence homology of this protein with the inner mitochondrial membrane transporters suggested a domain structure in which the N- and C-termini of the protein are located on the mitochondrial intermembrane-facing surface, with six membrane-spanning regions interspersed by two intermembrane loops and three matrix-facing loops. We now report the functional significance of insertion of the c-myc epitope into the intermembrane loops and of a series of site-directed mutations at hamster MFT residues highly conserved in orthologues. Insertional mutagenesis in the first predicted intermembrane loop eliminated MFT function, but the introduction of a c-myc peptide into the second loop was without effect. Most of the hamster MFT residues studied by site-directed mutagenesis were remarkably resilient to these mutations, except for R249A and G192E, both of which eliminated folate transport activity. Homology modeling, using the crystal structure of the bovine ADP/ATP carrier (AAC) as a scaffold, suggested a similar three-dimensional structure for the MFT and the AAC. An ion-pair interaction in the AAC thought to be central to the mechanism of membrane penetration by ADP is predicted by this homology model to be replaced by a pi-cation interaction in MFT orthologues and probably also in other members of the family bearing the P(I/L)W motif. This model suggests that the MFT R249A and G192E mutations both modify the base of a basket-shaped structure that appears to constitute a trap door for the flux of folates into the mitochondrial matrix.
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Affiliation(s)
- Erin Perchiniak
- Department of Pharmacology and Toxicology and Massey Cancer Center, Virginia Commonwealth University, Richmond, Virginia 23298, USA
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634
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Ma C, Remani S, Sun J, Kotaria R, Mayor JA, Walters DE, Kaplan RS. Identification of the substrate binding sites within the yeast mitochondrial citrate transport protein. J Biol Chem 2007; 282:17210-20. [PMID: 17400551 DOI: 10.1074/jbc.m611268200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The objective of the present investigation was to identify the substrate binding site(s) within the yeast mitochondrial citrate transport protein (CTP). Our strategy involved kinetically characterizing 30 single-Cys CTP mutants that we had previously constructed based on their hypothesized importance in the structure-based mechanism of this carrier. As part of these studies, a modified transport assay was developed that permitted, for the first time, the accurate determination of K(m) values that were elevated >100-fold compared with the Cys-less control value. We identified 10 single-Cys CTP mutants that displayed sharply elevated K(m) values (i.e. 5 to >300-fold). Each of these mutants displayed V(max) values that were reduced by > or = 98% and resultant catalytic efficiencies that were reduced by > or = 99.9%. Importantly, superposition of this functional data onto the three-dimensional homology-modeled CTP structure, which we previously had developed, revealed that nine of these ten residues form two topographically distinct clusters. Additional modeling showed that: (i) each cluster is capable of forming numerous hydrogen bonds with citrate and (ii) the two clusters are sufficiently distant from one another such that citrate is unlikely to interact with all of these residues at the same time. We deduced from these findings that the CTP contains at least two citrate binding sites per monomer, which are located at increasing depths within the translocation pathway. The identification of these sites, combined with an initial assessment of the citrate-amino acid side-chain interactions that may occur at these sites, substantially extends our understanding of CTP functioning at the molecular level.
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Affiliation(s)
- Chunlong Ma
- Department of Biochemistry and Molecular Biology, Rosalind Franklin University of Medicine and Science, The Chicago Medical School, North Chicago, Illinois 60064, USA
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635
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Hu M, Campbell BE, Pellegrino M, Loukas A, Beveridge I, Ranganathan S, Gasser RB. Genomic characterization of Tv-ant-1, a Caenorhabditis elegans tag-61 homologue from the parasitic nematode Trichostrongylus vitrinus. Gene 2007; 397:12-25. [PMID: 17512141 DOI: 10.1016/j.gene.2007.03.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2007] [Revised: 03/19/2007] [Accepted: 03/24/2007] [Indexed: 10/23/2022]
Abstract
A full-length cDNA (Tv-ant-1) encoding an adenine nucleotide translocator (ANT or ADP/ATP translocase) (Tv-ANT-1) was isolated from Trichostrongylus vitrinus (order Strongylida), an economically important parasitic nematode of small ruminants. The uninterrupted open reading frame (ORF) of 894 nucleotides encoded a predicted protein of 297 amino acids, containing characteristic motifs [RRRMMM] and PX(D,E)XX(K,R). Comparison with selected sequences from the free-living nematode Caenorhabditis elegans, cattle and human showed that Tv-ANT-1 is relatively conserved. Sequence identity was the greatest in and near the consensus sequence RRRMMM, and in the six hydrophobic regions predicted to be associated with alpha-helices and to traverse the cell membrane. Phylogenetic analyses of selected amino acid sequence data, using the neighbor-joining and maximum parsimony methods, revealed Tv-ANT-1 to be most closely related to the molecule (Ce-ANT-3) inferred from the tag-61 gene of C. elegans. Comparison of the genomic organization of the full-length Tv-ant-1 gene was similar to that of tag-61. Analysis of the region (5'-UTR) upstream of Tv-ant-1 identified some promoter components, including GATA transcription factor, CAAT and E-box elements. Transcriptional analysis by reverse transcription polymerase chain reaction (RT-PCR) showed that Tv-ant-1 was transcribed in all developmental stages of T. vitrinus, including the first- to fourth- stage larvae (L(1)-L(4)) as well as female and male adults. RNA interference, conducted by feeding C. elegans with double-stranded RNA (dsRNA) from Tv-ant-1 cDNA (using the homologous gene from C. elegans as a positive control), revealed no gene silencing. In spite of nucleotide identities of 100% in 23-30 bp stretches of sequence between the genes Tv-ant-1 and tag-61, these identities seem to be insufficient to achieve effective silencing in C. elegans using the parasite homologue/orthologue Tv-ant-1. This first insight into an ANT of T. vitrinus provides a foundation for exploring its role in developmental and/or survival processes of trichostrongylid nematodes.
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Affiliation(s)
- Min Hu
- Department of Veterinary Science, The University of Melbourne, Werribee, Victoria, Australia
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636
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Coonrod EM, Karren MA, Shaw JM. Ugo1p Is a Multipass Transmembrane Protein with a Single Carrier Domain Required for Mitochondrial Fusion. Traffic 2007; 8:500-11. [PMID: 17451553 DOI: 10.1111/j.1600-0854.2007.00550.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The outer mitochondrial membrane protein Ugo1 forms a complex with the Fzo1p and Mgm1p GTPases that regulates mitochondrial fusion in yeast. Ugo1p contains two putative carrier domains (PCDs) found in mitochondrial carrier proteins (MCPs). Mitochondrial carrier proteins are multipass transmembrane proteins that actively transport molecules across the inner mitochondrial membrane. Mitochondrial carrier protein transport requires functional carrier domains with the consensus sequence PX(D/E)XX(K/R). Mutation of charged residues in this consensus sequence disrupts transport function. In this study, we used targeted mutagenesis to show that charge reversal mutations in Ugo1p PCD2, but not PCD1, disrupt mitochondrial fusion. Ugo1p is reported to be a single-pass transmembrane protein despite the fact that it contains several additional predicted transmembrane segments. Using a combination of protein targeting and membrane extraction experiments, we provide evidence that Ugo1p contains additional transmembrane domains and is likely a multipass transmembrane protein. These studies identify PCD2 as a functional domain of Ugo1p and provide the first experimental evidence for a multipass topology of this essential fusion component.
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Affiliation(s)
- Emily M Coonrod
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97401, USA
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637
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Cappello AR, Miniero DV, Curcio R, Ludovico A, Daddabbo L, Stipani I, Robinson AJ, Kunji ERS, Palmieri F. Functional and structural role of amino acid residues in the odd-numbered transmembrane alpha-helices of the bovine mitochondrial oxoglutarate carrier. J Mol Biol 2007; 369:400-12. [PMID: 17442340 DOI: 10.1016/j.jmb.2007.03.048] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2006] [Revised: 03/16/2007] [Accepted: 03/19/2007] [Indexed: 11/30/2022]
Abstract
The mitochondrial oxoglutarate carrier (OGC) plays an important role in the malate-aspartate shuttle, the oxoglutarate-isocitrate shuttle and gluconeogenesis. To establish amino acid residues that are important for function, each residue in the transmembrane alpha-helices H1, H3 and H5 was replaced systematically by a cysteine in a fully functional mutant carrier that was devoid of cysteine residues. The transport activity of the mutant carriers was measured in the presence and absence of sulfhydryl reagents. The observed effects were rationalized by using a comparative structural model of the OGC. Most of the residues that are critical for function are found at the bottom of the cavity and they belong to the signature motifs P-X-[DE]-X-X-[KR] that form a network of three inter-helical salt bridges that close the carrier at the matrix side. The OGC deviates from most other carriers, because it has a conserved leucine (L144) rather than a positively charged residue in the signature motif of the second repeat and thus the salt bridge network is lacking one salt bridge. Incomplete salt-bridge networks due to hydrophobic, aromatic or polar substitutions are observed in other dicarboxylate, phosphate and adenine nucleotide transporters. The interaction between the carrier and the substrate has to provide the activation energy to trigger the re-arrangement of the salt-bridge network and other structural changes required for substrate translocation. For substrates such as malate, which has only two carboxylic and one hydroxyl group, a reduction in the number of salt bridges in the network may be required to lower the energy barrier for translocation. Another group of key residues, consisting of T36, A134, and T233, is close to the putative substrate binding site and substitutions or modifications of these residues may interfere with substrate binding and ion coupling. Residues G32, A35, Q40, G130, G133, A134, G230, and S237 are potentially engaged in inter-helical interactions and they may be involved in the movements of the alpha-helices during translocation.
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Affiliation(s)
- Anna R Cappello
- Department of Pharmaco-Biology, Laboratory of Biochemistry and Molecular Biology, University of Bari, Via E. Orabona 4, 70125 Bari, Italy
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638
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Bensalem N, Masscheleyn S, Mozo J, Vallée B, Brouillard F, Trudel S, Ricquier D, Edelman A, Guerrera IC, Miroux B. High Sensitivity Identification of Membrane Proteins by MALDI TOF-MASS Spectrometry Using Polystyrene Beads. J Proteome Res 2007; 6:1595-602. [PMID: 17355127 DOI: 10.1021/pr0606272] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Membrane proteins play a large variety of functions in life and represent 30% of all genomes sequenced. Due to their hydrophobic nature, they are tightly bound to their biological membrane, and detergents are always required to extract and isolate them before identification by mass spectrometry (MS). The latter, however remains difficult. Peptide mass fingerprinting methods using techniques such as MALDI-TOF MS, for example, have become an important analytical tool in the identification of proteins. However, PMF of membrane proteins is a real challenge for at least three reasons. First, membrane proteins are naturally present at low levels; second, most of the detergents strongly inhibit proteases and have deleterious effects on MALDI spectra; and third, despite the presence of detergent, membrane proteins are unstable and often aggregate. We took the mitochondrial uncoupling protein 1 (UCP1) as a model and showed that differential acetonitrile extraction of tryptic peptides combined with the use of polystirene Bio-Beads triggered high resolution of the MALDI-TOF identification of mitochondrial membrane proteins solubilized either with Triton-X100 or CHAPS detergents.
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639
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Colasante C, Alibu VP, Kirchberger S, Tjaden J, Clayton C, Voncken F. Characterization and developmentally regulated localization of the mitochondrial carrier protein homologue MCP6 from Trypanosoma brucei. EUKARYOTIC CELL 2007; 5:1194-205. [PMID: 16896205 PMCID: PMC1539146 DOI: 10.1128/ec.00096-06] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Proteins of the mitochondrial carrier family (MCF) are located mainly in the inner mitochondrial membrane and mediate the transport of a large range of metabolic intermediates. The genome of Trypanosoma brucei harbors 29 genes encoding different MCF proteins. We describe here the characterization of MCP6, a novel T. brucei MCF protein. Sequence comparison and phylogenetic reconstruction revealed that MCP6 is closely related to different mitochondrial ADP/ATP and calcium-dependent solute carriers, including the ATP-Mg/Pi carrier of Homo sapiens. However, MCP6 lacks essential amino acids and sequence motifs conserved in these metabolite transporters, and functional reconstitution and transport assays with E. coli suggested that this protein indeed does not function as an ADP/ATP or ATP-Mg/Pi carrier. The subcellular localization of MCP6 is developmentally regulated: in bloodstream-form trypanosomes, the protein is predominantly glycosomal, whereas in the procyclic form, it is found mainly in the mitochondria. Depletion of MCP6 in procyclic trypanosomes resulted in growth inhibition, an increased cell size, aberrant numbers of nuclei and kinetoplasts, and abnormal kinetoplast morphology, suggesting that depletion of MCP6 inhibits division of the kinetoplast.
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Affiliation(s)
- Claudia Colasante
- Zentrum für Molekulare Biologie (ZMBH), Im Neuenheimer Feld 282, D-69120 Heidelberg, Germany
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640
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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.
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Affiliation(s)
- H Nury
- Institut de Biologie Structurale Jean-Pierre Ebel, UMR 5075 CEA-CNRS-Université Joseph Fourier, F-38027 Grenoble cedex 1, France.
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641
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Thuswaldner S, Lagerstedt JO, Rojas-Stütz M, Bouhidel K, Der C, Leborgne-Castel N, Mishra A, Marty F, Schoefs B, Adamska I, Persson BL, Spetea C. Identification, expression, and functional analyses of a thylakoid ATP/ADP carrier from Arabidopsis. J Biol Chem 2007; 282:8848-59. [PMID: 17261580 DOI: 10.1074/jbc.m609130200] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
In plants the chloroplast thylakoid membrane is the site of light-dependent photosynthetic reactions coupled to ATP synthesis. The ability of the plant cell to build and alter this membrane system is essential for efficient photosynthesis. A nucleotide translocator homologous to the bovine mitochondrial ADP/ATP carrier (AAC) was previously found in spinach thylakoids. Here we have identified and characterized a thylakoid ATP/ADP carrier (TAAC) from Arabidopsis.(i) Sequence homology with the bovine AAC and the prediction of chloroplast transit peptides indicated a putative carrier encoded by the At5g01500 gene, as a TAAC. (ii) Transiently expressed TAAC-green fluorescent protein fusion construct was targeted to the chloroplast. Western blotting using a peptide-specific antibody together with immunogold electron microscopy revealed a major location of TAAC in the thylakoid membrane. Previous proteomic analyses identified this protein in chloroplast envelope preparations. (iii) Recombinant TAAC protein specifically imports ATP in exchange for ADP across the cytoplasmic membrane of Escherichia coli. Studies on isolated thylakoids from Arabidopsis confirmed these observations. (iv) The lack of TAAC in an Arabidopsis T-DNA insertion mutant caused a 30-40% reduction in the thylakoid ATP transport and metabolism. (v) TAAC is readily expressed in dark-grown Arabidopsis seedlings, and its level remains stable throughout the greening process. Its expression is highest in developing green tissues and in leaves undergoing senescence or abiotic stress. We propose that the TAAC protein supplies ATP for energy-dependent reactions during thylakoid biogenesis and turnover in plants.
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Affiliation(s)
- Sophie Thuswaldner
- Division of Cell Biology, Linköping University, SE-581 85 Linköping, Sweden
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642
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Rapp M, Seppälä S, Granseth E, von Heijne G. Emulating Membrane Protein Evolution by Rational Design. Science 2007; 315:1282-4. [PMID: 17255477 DOI: 10.1126/science.1135406] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
How do integral membrane proteins evolve in size and complexity? Using the small multidrug-resistance protein EmrE from Escherichia coli as a model, we experimentally demonstrated that the evolution of membrane proteins composed of two homologous but oppositely oriented domains can occur in a small number of steps: An original dual-topology protein evolves, through a gene-duplication event, to a heterodimer formed by two oppositely oriented monomers. This simple evolutionary pathway can explain the frequent occurrence of membrane proteins with an internal pseudo-two-fold symmetry axis in the plane of the membrane.
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Affiliation(s)
- Mikaela Rapp
- Center for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
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643
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Monné M, Robinson AJ, Boes C, Harbour ME, Fearnley IM, Kunji ERS. The mimivirus genome encodes a mitochondrial carrier that transports dATP and dTTP. J Virol 2007; 81:3181-6. [PMID: 17229695 PMCID: PMC1866048 DOI: 10.1128/jvi.02386-06] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Members of the mitochondrial carrier family have been reported in eukaryotes only, where they transport metabolites and cofactors across the mitochondrial inner membrane to link the metabolic pathways of the cytosol and the matrix. The genome of the giant virus Mimiviridae mimivirus encodes a member of the mitochondrial carrier family of transport proteins. This viral protein has been expressed in Lactococcus lactis and is shown to transport dATP and dTTP. As the 1.2-Mb double-stranded DNA mimivirus genome is rich in A and T residues, we speculate that the virus is using this protein to target the host mitochondria as a source of deoxynucleotides for its replication.
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Affiliation(s)
- Magnus Monné
- Dunn Human Nutrition Unit, Medical Research Council, Hills Road, Cambridge CB2 2XY, United Kingdom
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644
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Satrústegui J, Pardo B, Del Arco A. Mitochondrial Transporters as Novel Targets for Intracellular Calcium Signaling. Physiol Rev 2007; 87:29-67. [PMID: 17237342 DOI: 10.1152/physrev.00005.2006] [Citation(s) in RCA: 203] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Ca2+signaling in mitochondria is important to tune mitochondrial function to a variety of extracellular stimuli. The main mechanism is Ca2+entry in mitochondria via the Ca2+uniporter followed by Ca2+activation of three dehydrogenases in the mitochondrial matrix. This results in increases in mitochondrial NADH/NAD ratios and ATP levels and increased substrate uptake by mitochondria. We review evidence gathered more than 20 years ago and recent work indicating that substrate uptake, mitochondrial NADH/NAD ratios, and ATP levels may be also activated in response to cytosolic Ca2+signals via a mechanism that does not require the entry of Ca2+in mitochondria, a mechanism depending on the activity of Ca2+-dependent mitochondrial carriers (CaMC). CaMCs fall into two groups, the aspartate-glutamate carriers (AGC) and the ATP-Mg/Picarriers, also named SCaMC (for short CaMC). The two mammalian AGCs, aralar and citrin, are members of the malate-aspartate NADH shuttle, and citrin, the liver AGC, is also a member of the urea cycle. Both types of CaMCs are activated by Ca2+in the intermembrane space and function together with the Ca2+uniporter in decoding the Ca2+signal into a mitochondrial response.
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Affiliation(s)
- Jorgina Satrústegui
- Departamento de Biología Molecular Centro de Biología Molecular "Severo Ochoa" UAM-CSIC, Facultad de Ciencias, Universidad Autónoma, Madrid, Spain.
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645
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Kihira Y, Ueno M, Terada H. Difference between Yeast and Bovine Mitochondrial ADP/ATP Carriers in Terms of Conformational Properties of the First Matrix Loop as Deduced by Use of Copper-o-phenanthroline. Biol Pharm Bull 2007; 30:885-90. [PMID: 17473430 DOI: 10.1248/bpb.30.885] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The mitochondrial ADP/ATP carrier (AAC) has 6 transmembrane regions and 3 matrix loops. Our previous mutational study on the Cys residue in the LM1s of chimeric bovine type 1 AAC (yN-bAAC1), in which the N-terminal 11 amino acids of bovine type 1 AAC are substituted with the corresponding 26 amino acids of yeast type 2 AAC (yAAC2), and yAAC2 in the yeast expression system suggested the possibility of a different structural feature between their LM1s. In the present study, we compared the effects of the SH cross-linking reagent copper-o-phenanthroline (Cu(OP)(2)) on yN-bAAC1 and yAAC2 in order to study the difference between these LM1s of the 2 carriers. Cu(OP)(2) is known to cross-link 2 AAC molecules in a functional dimer via a Cys residue in each first matrix loop (LM1). yN-bAAC1 exhibited intra- and inter-molecular cross-linking, in agreement with the results of a previous study on the native bovine carrier and suggesting that yN-bAAC1 had the same structure as the native carrier. yAAC2 also showed intra- and inter-molecular cross-linking. However, the speed of formation of the inter-molecular cross-linking of yN-bAAC1 was faster than that of yAAC2, suggesting that the conformational state of the LM1 was different between the 2 carriers. In addition, we also studied the effects of AAC-specific inhibitors and solubilization with Triton X-100 on the cross-linking.
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Affiliation(s)
- Yoshitaka Kihira
- Faculty of Pharmaceutical Sciences, University of Toyama, Toyama, Japan.
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646
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Falconi M, Chillemi G, Di Marino D, D'Annessa I, Morozzo della Rocca B, Palmieri L, Desideri A. Structural dynamics of the mitochondrial ADP/ATP carrier revealed by molecular dynamics simulation studies. Proteins 2006; 65:681-91. [PMID: 16988954 DOI: 10.1002/prot.21102] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The mitochondrial adenosine diphosphate/adenosine triphosphate (ADP/ATP) carrier has been recently crystallized in complex with its specific inhibitor carboxyatractyloside (CATR). In the crystal structure, the six-transmembrane helix bundle that defines the nucleotide translocation pathway is closed on the matrix side due to sharp kinks in the odd-numbered helices. The closed conformation is further sealed by the loops protruding into the matrix that interact through an intricate network of charge-pairs. To gain insight into its structural dynamics we performed molecular dynamics (MD) simulation studies of the ADP/ATP carrier with and without its cocrystallized inhibitor. The two trajectories sampled a conformational space around two different configurations characterized by distinct salt-bridge networks with a significant shift from inter- to intrarepeat bonding on the matrix side in the absence of CATR. Analysis of the geometrical parameters defining the transmembrane helices showed that even-numbered helices can undergo a face rotation, whereas odd-numbered helices can undergo a change in the wobble angle with a conserved proline acting as molecular hinge. Our results provide new information on the dynamical properties of the ADP/ATP carrier and for the first time yield a detailed picture of a stable carrier conformation in absence of the inhibitor.
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Affiliation(s)
- M Falconi
- Department of Biology, University of Rome Tor Vergata, Rome, Italy
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647
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Bamber L, Harding M, Butler PJG, Kunji ERS. Yeast mitochondrial ADP/ATP carriers are monomeric in detergents. Proc Natl Acad Sci U S A 2006; 103:16224-9. [PMID: 17056710 PMCID: PMC1618811 DOI: 10.1073/pnas.0607640103] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2006] [Indexed: 11/18/2022] Open
Abstract
Mitochondrial carriers are believed widely to be homodimers both in the inner membrane of the organelle and in detergents. The dimensions and molecular masses of the detergent and protein-detergent micelles were measured for yeast ADP/ATP carriers in a range of different detergents. The radius of the carrier at the midpoint of the membrane, its average radius, its Stokes' radius, its molecular mass, and its excluded volume were determined. These parameters are consistent with the known structural model of the bovine ADP/ATP carrier and they demonstrate that the yeast mitochondrial ADP/ATP carriers are monomeric in detergents. Therefore, models of substrate transport have to be considered in which the carrier operates as a monomer rather than as a dimer.
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Affiliation(s)
| | | | - P. Jonathan G. Butler
- Laboratory of Molecular Biology, Medical Research Council, Hills Road, CB2 2XY Cambridge, United Kingdom
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648
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Ziemys A, Toleikis A, Kopustinskiene DM. Molecular modelling of K(ATP) channel blockers-ADP/ ATP carrier interactions. ACTA ACUST UNITED AC 2006; 153:390-3. [PMID: 16986324 DOI: 10.1049/ip-syb:20060007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The modelling of molecule-molecule interactions has been widely accepted as a tool for drug discovery and development studies. However, this powerful technique is unappreciated in physiological and biochemical studies, where it could be extremely useful for understanding the mechanisms of action of various compounds in cases when experimental data are controversial due to complexity of the investigated systems. In this study, based on the biochemical data suggesting involvement of mitochondrial ADP/ATP carrier in K+ and H+ transport to mitochondrial matrix molecular modelling is applied to elucidate the possible interactions between the ADP/ATP carrier and its putative ligands--K(ATP) channel blockers glybenclamide, tolbutamide and 5-hydroxydecanoate. Results revealed that K(ATP) channel blockers could bind to the specific location proximal to H1, H4, H5 and H6 transmembrane helices within the cavity of the ADP/ ATP carrier. Analysis of the predicted binding site suggests that K(ATP) channel blockers could interfere with both the ADP/ATP translocation and possible cation flux through the ADP/ATP carrier, and supports the hypothesis that the ADP/ATP carrier is a target of K(ATP) channel modulators.
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Affiliation(s)
- A Ziemys
- Department of Biology, Vytautas Magnus University, Vileikos 8, LT-44404 Kaunas, Lithuania.
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649
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Kim YH, Haidl G, Schaefer M, Egner U, Herr JC. Compartmentalization of a unique ADP/ATP carrier protein SFEC (Sperm Flagellar Energy Carrier, AAC4) with glycolytic enzymes in the fibrous sheath of the human sperm flagellar principal piece. Dev Biol 2006; 302:463-76. [PMID: 17137571 PMCID: PMC1858657 DOI: 10.1016/j.ydbio.2006.10.004] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2006] [Revised: 09/28/2006] [Accepted: 10/04/2006] [Indexed: 11/17/2022]
Abstract
The longest part of the sperm flagellum, the principal piece, contains the fibrous sheath, a cytoskeletal element unique to spermiogenesis. We performed mass spectrometry proteomics on isolated human fibrous sheaths identifying a unique ADP/ATP carrier protein, SFEC [AAC4], seven glycolytic enzymes previously unreported in the human sperm fibrous sheath, and sorbitol dehydrogenase. SFEC, pyruvate kinase and aldolase were co-localized by immunofluorescence to the principal piece. A homology model constructed for SFEC predicted unique residues at the entrance to the nucleotide binding pocket of SFEC that are absent in other human ADP/ATP carriers, suggesting opportunities for selective drug targeting. This study provides the first evidence of a role for an ADP/ATP carrier family member in glycolysis. The co-localization of SFEC and glycolytic enzymes in the fibrous sheath supports a growing literature that the principal piece of the flagellum is capable of generating and regulating ATP independently from mitochondrial oxidation in the mid-piece. A model is proposed that the fibrous sheath represents a highly ordered complex, analogous to the electron transport chain, in which adjacent enzymes in the glycolytic pathway are assembled to permit efficient flux of energy substrates and products with SFEC serving to mediate energy generating and energy consuming processes in the distal flagellum, possibly as a nucleotide shuttle between flagellar glycolysis, protein phosphorylation and mechanisms of motility.
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Affiliation(s)
- Young-Hwan Kim
- Center for Research in Contraceptive and Reproductive Health, Department of Cell Biology, University of Virginia, Charlottesville, Virginia 22908 U.S.A
| | - Gerhard Haidl
- Department of Dermatology/Andrology Unit, University of Bonn, Bonn, Germany
| | - Martina Schaefer
- Research Center Europe, Enabling Technologies, Schering AG, 13342 Berlin, Germany
| | - Ursula Egner
- Research Center Europe, Enabling Technologies, Schering AG, 13342 Berlin, Germany
| | - John C. Herr
- Center for Research in Contraceptive and Reproductive Health, Department of Cell Biology, University of Virginia, Charlottesville, Virginia 22908 U.S.A
- *Corresponding Author: John C. Herr, Department of Cell Biology, P.O. Box 800732, University of Virginia Health System, Charlottesville, Virginia 22908, Phone: (434) 924-2007, Fax (434) 982-3912, E-mail:
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650
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Abstract
Serotonin transporter (SERT) catalyzes reuptake of the neurotransmitter serotonin (5-HT) and is a target for antidepressant drugs and psychostimulants. It is a member of a large family of neurotransmitter and amino acid transporters. A recent study using site-directed cysteine modification identified a helical region of the transporter with high accessibility to the cytoplasm. Subsequently, the high resolution structure of LeuT, a prokaryotic homologue, showed that the residues corresponding to this helical region are part of the fifth transmembrane domain. The accessibility of these positions is now shown to depend on conformational changes corresponding to interconversion of SERT between two forms that face the extracellular medium and the cytoplasm, respectively. Binding of the extracellular inhibitor cocaine decreased accessibility at these positions, whereas 5-HT, the transported substrate, increased it. The effect of 5-HT required the simultaneous presence of Na+ and Cl-, which are transported into the cell together (symported) with 5-HT. In light of the LeuT structure, these results begin to define the pathway through which 5-HT diffuses between its binding site and the cytoplasm. They also confirm a prediction of the alternating access model for transport, namely, that all symported substrates must bind together before translocation.
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Affiliation(s)
- Yuan-Wei Zhang
- Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520-8066, USA
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