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Astashkin R, Kovalev K, Bukhdruker S, Vaganova S, Kuzmin A, Alekseev A, Balandin T, Zabelskii D, Gushchin I, Royant A, Volkov D, Bourenkov G, Koonin E, Engelhard M, Bamberg E, Gordeliy V. Structural insights into light-driven anion pumping in cyanobacteria. Nat Commun 2022; 13:6460. [PMID: 36309497 PMCID: PMC9617919 DOI: 10.1038/s41467-022-34019-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Accepted: 10/11/2022] [Indexed: 12/25/2022] Open
Abstract
Transmembrane ion transport is a key process in living cells. Active transport of ions is carried out by various ion transporters including microbial rhodopsins (MRs). MRs perform diverse functions such as active and passive ion transport, photo-sensing, and others. In particular, MRs can pump various monovalent ions like Na+, K+, Cl-, I-, NO3-. The only characterized MR proposed to pump sulfate in addition to halides belongs to the cyanobacterium Synechocystis sp. PCC 7509 and is named Synechocystis halorhodopsin (SyHR). The structural study of SyHR may help to understand what makes an MR pump divalent ions. Here we present the crystal structure of SyHR in the ground state, the structure of its sulfate-bound form as well as two photoreaction intermediates, the K and O states. These data reveal the molecular origin of the unique properties of the protein (exceptionally strong chloride binding and proposed pumping of divalent anions) and sheds light on the mechanism of anion release and uptake in cyanobacterial halorhodopsins. The unique properties of SyHR highlight its potential as an optogenetics tool and may help engineer different types of anion pumps with applications in optogenetics.
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Affiliation(s)
- R. Astashkin
- grid.450307.50000 0001 0944 2786Univ. Grenoble Alpes, CEA, CNRS, Institut de Biologie Structurale (IBS), Grenoble, France
| | - K. Kovalev
- grid.475756.20000 0004 0444 5410European Molecular Biology Laboratory, Hamburg unit c/o DESY, Hamburg, Germany
| | - S. Bukhdruker
- grid.5398.70000 0004 0641 6373European Synchrotron Radiation Facility Grenoble, Grenoble, France ,grid.8385.60000 0001 2297 375XInstitute of Biological Information Processing (IBI-7: Structural Biochemistry), Forschungszentrum Jülich, Jülich, Germany ,grid.8385.60000 0001 2297 375XJuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich, Jülich, Germany
| | - S. Vaganova
- grid.8385.60000 0001 2297 375XInstitute of Biological Information Processing (IBI-7: Structural Biochemistry), Forschungszentrum Jülich, Jülich, Germany ,grid.8385.60000 0001 2297 375XJuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich, Jülich, Germany
| | - A. Kuzmin
- grid.18763.3b0000000092721542Research Center for Molecular Mechanisms of Aging and Age-related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - A. Alekseev
- grid.18763.3b0000000092721542Research Center for Molecular Mechanisms of Aging and Age-related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - T. Balandin
- grid.8385.60000 0001 2297 375XInstitute of Biological Information Processing (IBI-7: Structural Biochemistry), Forschungszentrum Jülich, Jülich, Germany ,grid.8385.60000 0001 2297 375XJuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich, Jülich, Germany
| | - D. Zabelskii
- grid.434729.f0000 0004 0590 2900European XFEL GmbH, Schenefeld, Germany
| | - I. Gushchin
- grid.18763.3b0000000092721542Research Center for Molecular Mechanisms of Aging and Age-related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - A. Royant
- grid.450307.50000 0001 0944 2786Univ. Grenoble Alpes, CEA, CNRS, Institut de Biologie Structurale (IBS), Grenoble, France ,grid.5398.70000 0004 0641 6373European Synchrotron Radiation Facility Grenoble, Grenoble, France
| | - D. Volkov
- grid.8385.60000 0001 2297 375XInstitute of Biological Information Processing (IBI-7: Structural Biochemistry), Forschungszentrum Jülich, Jülich, Germany ,grid.8385.60000 0001 2297 375XJuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich, Jülich, Germany
| | - G. Bourenkov
- grid.475756.20000 0004 0444 5410European Molecular Biology Laboratory, Hamburg unit c/o DESY, Hamburg, Germany
| | - E. Koonin
- grid.419234.90000 0004 0604 5429National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD USA
| | - M. Engelhard
- grid.418441.c0000 0004 0491 3333Department Structural Biochemistry, Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
| | - E. Bamberg
- grid.419494.50000 0001 1018 9466Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - V. Gordeliy
- grid.450307.50000 0001 0944 2786Univ. Grenoble Alpes, CEA, CNRS, Institut de Biologie Structurale (IBS), Grenoble, France ,grid.8385.60000 0001 2297 375XInstitute of Biological Information Processing (IBI-7: Structural Biochemistry), Forschungszentrum Jülich, Jülich, Germany ,grid.8385.60000 0001 2297 375XJuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich, Jülich, Germany
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Kovalev K, Volkov D, Astashkin R, Alekseev A, Gushchin I, Haro-Moreno JM, Chizhov I, Siletsky S, Mamedov M, Rogachev A, Balandin T, Borshchevskiy V, Popov A, Bourenkov G, Bamberg E, Rodriguez-Valera F, Büldt G, Gordeliy V. High-resolution structural insights into the heliorhodopsin family. Proc Natl Acad Sci U S A 2020; 117:4131-4141. [PMID: 32034096 PMCID: PMC7049168 DOI: 10.1073/pnas.1915888117] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Rhodopsins are the most abundant light-harvesting proteins. A new family of rhodopsins, heliorhodopsins (HeRs), has recently been discovered. Unlike in the known rhodopsins, in HeRs the N termini face the cytoplasm. The function of HeRs remains unknown. We present the structures of the bacterial HeR-48C12 in two states at the resolution of 1.5 Å, which highlight its remarkable difference from all known rhodopsins. The interior of HeR's extracellular part is completely hydrophobic, while the cytoplasmic part comprises a cavity (Schiff base cavity [SBC]) surrounded by charged amino acids and containing a cluster of water molecules, presumably being a primary proton acceptor from the Schiff base. At acidic pH, a planar triangular molecule (acetate) is present in the SBC. Structure-based bioinformatic analysis identified 10 subfamilies of HeRs, suggesting their diverse biological functions. The structures and available data suggest an enzymatic activity of HeR-48C12 subfamily and their possible involvement in fundamental redox biological processes.
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Affiliation(s)
- K Kovalev
- Institut de Biologie Structurale J.-P. Ebel, Université Grenoble Alpes-Commission for Atomic Energy (CEA)-CNRS, 38000 Grenoble, France
- Institute of Biological Information Processing (Institute of Biological Information Processing: Structural Biochemistry), Forschungszentrum Jülich, 52428 Jülich, Germany
- JuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich, 52428 Jülich, Germany
- Research Center for Mechanisms of Aging and Age Related Diseases, Moscow Institute of Physics and Technology (National Research University), Dolgoprudny 141701, Russia
- Institute of Crystallography, University of Aachen (Rheinisch-Westfälische Technische Hochschule Aachen [RWTH]), 52062 Aachen, Germany
| | - D Volkov
- Institute of Biological Information Processing (Institute of Biological Information Processing: Structural Biochemistry), Forschungszentrum Jülich, 52428 Jülich, Germany
- JuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich, 52428 Jülich, Germany
| | - R Astashkin
- Institut de Biologie Structurale J.-P. Ebel, Université Grenoble Alpes-Commission for Atomic Energy (CEA)-CNRS, 38000 Grenoble, France
- Research Center for Mechanisms of Aging and Age Related Diseases, Moscow Institute of Physics and Technology (National Research University), Dolgoprudny 141701, Russia
| | - A Alekseev
- Institute of Biological Information Processing (Institute of Biological Information Processing: Structural Biochemistry), Forschungszentrum Jülich, 52428 Jülich, Germany
- JuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich, 52428 Jülich, Germany
- Research Center for Mechanisms of Aging and Age Related Diseases, Moscow Institute of Physics and Technology (National Research University), Dolgoprudny 141701, Russia
- Institute of Crystallography, University of Aachen (Rheinisch-Westfälische Technische Hochschule Aachen [RWTH]), 52062 Aachen, Germany
| | - I Gushchin
- Research Center for Mechanisms of Aging and Age Related Diseases, Moscow Institute of Physics and Technology (National Research University), Dolgoprudny 141701, Russia
| | - J M Haro-Moreno
- Evolutionary Genomics Group, Departamento de Producción Vegetal y Microbiología, Universidad Miguel Hernández, 03202 San Juan de Alicante, Spain
| | - I Chizhov
- Institute for Biophysical Chemistry, Hannover Medical School, 30625 Hannover, Germany
| | - S Siletsky
- Belozersky Institute of Physical-Chemical Biology, Lomonosov Moscow State University, Moscow 119234, Russia
| | - M Mamedov
- Belozersky Institute of Physical-Chemical Biology, Lomonosov Moscow State University, Moscow 119234, Russia
| | - A Rogachev
- Research Center for Mechanisms of Aging and Age Related Diseases, Moscow Institute of Physics and Technology (National Research University), Dolgoprudny 141701, Russia
- Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna 141980, Russia
| | - T Balandin
- Institute of Biological Information Processing (Institute of Biological Information Processing: Structural Biochemistry), Forschungszentrum Jülich, 52428 Jülich, Germany
- JuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich, 52428 Jülich, Germany
| | - V Borshchevskiy
- Research Center for Mechanisms of Aging and Age Related Diseases, Moscow Institute of Physics and Technology (National Research University), Dolgoprudny 141701, Russia
| | - A Popov
- Structural Biology Group, European Synchrotron Radiation Facility, 38000 Grenoble, France
| | - G Bourenkov
- Hamburg Unit care of Deutsches Elektronen-Synchrotron (DESY), European Molecular Biology Laboratory, 22607 Hamburg, Germany
| | - E Bamberg
- Research Center for Mechanisms of Aging and Age Related Diseases, Moscow Institute of Physics and Technology (National Research University), Dolgoprudny 141701, Russia
- Biophysical Chemistry, Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany
| | - F Rodriguez-Valera
- Research Center for Mechanisms of Aging and Age Related Diseases, Moscow Institute of Physics and Technology (National Research University), Dolgoprudny 141701, Russia
- Evolutionary Genomics Group, Departamento de Producción Vegetal y Microbiología, Universidad Miguel Hernández, 03202 San Juan de Alicante, Spain
| | - G Büldt
- Research Center for Mechanisms of Aging and Age Related Diseases, Moscow Institute of Physics and Technology (National Research University), Dolgoprudny 141701, Russia
| | - V Gordeliy
- Institut de Biologie Structurale J.-P. Ebel, Université Grenoble Alpes-Commission for Atomic Energy (CEA)-CNRS, 38000 Grenoble, France;
- Institute of Biological Information Processing (Institute of Biological Information Processing: Structural Biochemistry), Forschungszentrum Jülich, 52428 Jülich, Germany
- JuStruct: Jülich Center for Structural Biology, Forschungszentrum Jülich, 52428 Jülich, Germany
- Research Center for Mechanisms of Aging and Age Related Diseases, Moscow Institute of Physics and Technology (National Research University), Dolgoprudny 141701, Russia
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Busch C, Ducki A, Bamberg E, Roscher S, Clasen J, Kalytta T, Liedtke G, Gloede D. Entwicklung und Evaluation eines Gesundheitsförderungsprogramms für Un- und Angelernte unter besonderer Berücksichtigung der Transfersicherung. Gesundheitswesen 2013; 77 Suppl 1:S129-30. [DOI: 10.1055/s-0033-1334893] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- C. Busch
- Arbeits- und Organisationspsychologie, Universität Hamburg
| | - A. Ducki
- Beuth Hochschule für Technik, Berlin
| | - E. Bamberg
- Arbeits- und Organisationspsychologie, Universität Hamburg
| | - S. Roscher
- Arbeits- und Organisationspsychologie, Universität Hamburg
| | - J. Clasen
- Arbeits- und Organisationspsychologie, Universität Hamburg
| | | | - G. Liedtke
- Sport- und Bewegungsmedizin, Universität Hamburg
| | - D. Gloede
- Beuth Hochschule für Technik, Berlin
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Sharma R, Tathireddy P, Lee S, Rieth L, Bamberg E, Dorval A, Normann R, Solzbacher F. Application-specific customizable architectures of Utah neural interfaces. ACTA ACUST UNITED AC 2011. [DOI: 10.1016/j.proeng.2011.12.250] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Abstract
Temperature jump experiments were carried out on purple membranes oriented and fixed in polyacrylamide gel. With green background illumination a relaxation of the photocurrent after an infrared laser pulse could be observed. To simulate the temperature jump signals different models of the bacteriorhodopsin photocycle were tested. The parameters of these models were obtained by measuring absorbance changes and photocurrent after excitation with a 575-nm laser flash.A model with a temperature-dependent branching before the M state turned out to be satisfying. Other models, especially those with a late branching or without branching, could not reproduce the temperature jump measurements.
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Affiliation(s)
- H J Butt
- Max-Planck-Institut für Biophysik, 6000 Frankfurt, Federal Republic of Germany
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Möstl E, Choi HS, Holzweber E, Bamberg E. Androstendion, Testosteron und Epitestosteron im Blut von Kühen während der ersten sechs Graviditätsmonate*. ACTA ACUST UNITED AC 2010. [DOI: 10.1111/j.1439-0442.1983.tb01018.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Bamberg E, Skolek R, Stöckl W. Verteilung der β-N-Acetylhexosaminidase und β-Galactosidase im Genitaltrakt des Hahnes (Gallus domesticus)*. ACTA ACUST UNITED AC 2010. [DOI: 10.1111/j.1439-0442.1976.tb01512.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Bamberg E, Choi HS, Hassaan NK, Kläring WJ, Möstl E, Stöckl W. Steroidhormongehalt in Blut und Ovarfollikeln des Rindes während des Zyklus*. ACTA ACUST UNITED AC 2010. [DOI: 10.1111/j.1439-0442.1980.tb01775.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Bamberg E, Kanout AG, Stöckl W, Ceska M, Choi HS. Gehalt an Testosteron und Luteinisierungshormon im Blutplasma von Stieren während des ersten Lebensjahres*. ACTA ACUST UNITED AC 2010. [DOI: 10.1111/j.1439-0442.1978.tb00901.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Bamberg E, Sinowatz F, Kanout AG. Biochemische und histochemische Untersuchungen über die Verteilung der β-N-Acetylhexosaminidase im Nebenhoden des Hundes. ACTA ACUST UNITED AC 2010. [DOI: 10.1111/j.1439-0442.1979.tb01767.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Möstl E, Choi HS, Kruip TAM, Bamberg E. Androstendion, Epitestosteron, Testosteron und Luteinisierungshormon im Blutplasma von Stieren vor und nach Verabreichung von Gn-RH (Lutal®)3. ACTA ACUST UNITED AC 2010. [DOI: 10.1111/j.1439-0442.1983.tb01002.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Zimmermann U, Rüger S, Shapira O, Westhoff M, Wegner LH, Reuss R, Gessner P, Zimmermann G, Israeli Y, Zhou A, Schwartz A, Bamberg E, Zimmermann D. Effects of environmental parameters and irrigation on the turgor pressure of banana plants measured using the non-invasive, online monitoring leaf patch clamp pressure probe. Plant Biol (Stuttg) 2010; 12:424-436. [PMID: 20522178 DOI: 10.1111/j.1438-8677.2009.00235.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Turgor pressure provides a sensitive indicator for irrigation scheduling. Leaf turgor pressure of Musa acuminate was measured by using the so-called leaf patch clamp pressure probe, i.e. by application of an external, magnetically generated and constantly retained clamp pressure to a leaf patch and determination of the attenuated output pressure P(p) that is highly correlated with the turgor pressure. Real-time recording of P(p) values was made using wireless telemetric transmitters, which send the data to a receiver base station where data are logged and transferred to a GPRS modem linked to an Internet server. Probes functioned over several months under field and laboratory conditions without damage to the leaf patch. Measurements showed that the magnetic-based probe could monitor very sensitively changes in turgor pressure induced by changes in microclimate (temperature, relative humidity, irradiation and wind) and irrigation. Irrigation effects could clearly be distinguished from environmental effects. Interestingly, oscillations in stomatal aperture, which occurred frequently below turgor pressures of 100 kPa towards noon at high transpiration or at high wind speed, were reflected in the P(p) values. The period of pressure oscillations was comparable with the period of oscillations in transpiration and photosynthesis. Multiple probe readings on individual leaves and/or on several leaves over the entire height of the plants further emphasised the great impact of this non-invasive turgor pressure sensor system for elucidating the dynamics of short- and long-distance water transport in higher plants.
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Affiliation(s)
- U Zimmermann
- Lehrstuhl für Biotechnologie, Biozentrum, Universität Würzburg, Würzburg, Germany.
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Westhoff M, Reuss R, Zimmermann D, Netzer Y, Gessner A, Gessner P, Zimmermann G, Wegner LH, Bamberg E, Schwartz A, Zimmermann U. A non-invasive probe for online-monitoring of turgor pressure changes under field conditions. Plant Biol (Stuttg) 2009; 11:701-12. [PMID: 19689778 DOI: 10.1111/j.1438-8677.2008.00170.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
An advanced non-invasive, field-suitable and inexpensive leaf patch clamp pressure probe for online-monitoring of the water relations of intact leaves is described. The probe measures the attenuated output patch clamp pressure, P(p), of a clamped leaf in response to an externally applied input pressure, P(clamp). P(clamp) is generated magnetically. P(p) is sensed by a pressure sensor integrated into the magnetic clamp. The magnitude of P(p) depends on the transfer function, T(f), of the leaf cells. T(f) consists of a turgor pressure-independent (related to the compression of the cuticle, cell walls and other structural elements) and a turgor pressure-dependent term. T(f) is dimensionless and assumes values between 0 and 1. Theory shows that T(f) is a power function of cell turgor pressure P(c). Concomitant P(p) and P(c) measurements on grapevines confirmed the relationship between T(f) and P(c). P(p) peaked if P(c) approached zero and assumed low values if P(c) reached maximum values. The novel probe was successfully tested on leaves of irrigated and non-irrigated grapevines under field conditions. Data show that slight changes in the microclimate and/or water supply (by irrigation or rain) are reflected very sensitively in P(p).
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Affiliation(s)
- M Westhoff
- Lehrstuhl für Biotechnologie, Biozentrum, Universität Würzburg, Würzburg, Germany
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Westhoff M, Zimmermann D, Schneider H, Wegner LH, Gessner P, Jakob P, Bamberg E, Shirley S, Bentrup FW, Zimmermann U. Evidence for discontinuous water columns in the xylem conduit of tall birch trees. Plant Biol (Stuttg) 2009; 11:307-327. [PMID: 19470103 DOI: 10.1111/j.1438-8677.2008.00124.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The continuity of the xylem water columns was studied on 17- to 23-m tall birch trees (trunk diameter about 23 cm; first branching above 10 m) all year round. Fifty-one trees were felled, and 5-cm thick slices or 2-m long boles were taken at regular, relatively short intervals over the entire height of the trees. The filling status of the vessels was determined by (i) xylem sap extraction from trunk and branch pieces (using the gas bubble-based jet-discharge method and centrifugation) and from trunk boles (using gravity discharge); (ii) (1)H nuclear magnetic resonance imaging of slice pieces; (iii) infusion experiments (dye, (86)Rb(+), D(2)O) on intact trees and cut branches; and (iv) xylem pressure measurements. This broad array of techniques disclosed no evidence for continuous water-filled columns, as postulated by the Cohesion-Tension theory, for root to apex directed mass transport. Except in early spring (during the xylem refilling phase) and after extremely heavy rainfall during the vegetation period, cohesive/mobile water was found predominantly at intermediate heights of the trunks but not at the base or towards the top of the tree. Similar results were obtained for branches. Furthermore, upper branches generally contained more cohesive/mobile water than lower branches. The results suggest that water lifting occurs by short-distance (capillary, osmotic and/or transpiration-bound) tension gradients as well as by mobilisation of water in the parenchymatic tissues and the heartwood, and by moisture uptake through lenticels.
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Affiliation(s)
- M Westhoff
- Lehrstuhl für Biotechnologie, Biozentrum, Universität Würzburg, Würzburg, Germany
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Westhoff M, Schneider H, Zimmermann D, Mimietz S, Stinzing A, Wegner LH, Kaiser W, Krohne G, Shirley S, Jakob P, Bamberg E, Bentrup FW, Zimmermann U. The mechanisms of refilling of xylem conduits and bleeding of tall birch during spring. Plant Biol (Stuttg) 2008; 10:604-623. [PMID: 18761499 DOI: 10.1111/j.1438-8677.2008.00062.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Seasonal variations in osmolality and components of xylem sap in tall birch trees were determined using several techniques. Xylem sap was extracted from branch and trunk sections of 58 trees using the very rapid gas bubble-based jet-discharge method. The 5-cm long wood pieces were taken at short intervals over the entire tree height. The data show that large biphasic osmolality gradients temporarily exist within the conducting xylem conduits during leaf emergence (up to 272 mosmol x kg(-1) at the apex). These gradients (arising mainly from glucose and fructose) were clearly held within the xylem conduit as demonstrated by (1)H NMR imaging of intact twigs. Refilling experiments with benzene, sucrose infusion, electron and light microscopy, as well as (1)H NMR chemical shift microimaging provided evidence that the xylem of birch represents a compartment confined by solute-reflecting barriers (radial: lipid linings/lipid bodies; axial: presumably air-filled spaces). These features allow transformation of osmolality gradients into osmotic pressure gradients. Refilling of the xylem occurs by a dual mechanism: from the base (by root pressure) and from the top (by hydrostatic pressure generated by xylem-bound osmotic pressure). The generation of osmotic pressure gradients was accompanied by bleeding. Bleeding could be observed at a height of up to 21 m. Bleeding rates measured at a given height decreased exponentially with time. Evidence is presented that the driving force for bleeding is the weight of the static water columns above the bleeding point. The pressure exerted by the water columns and the bleeding volume depend on the water-filling status of (communicating) vessels.
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Affiliation(s)
- M Westhoff
- Lehrstuhl für Biotechnologie, Biozentrum, Universität Würzburg, Würzburg, Germany
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Zimmermann D, Zhou A, Kiesel M, Feldbauer K, Terpitz U, Haase W, Schneider-Hohendorf T, Bamberg E, Sukhorukov VL. Effects on capacitance by overexpression of membrane proteins. Biochem Biophys Res Commun 2008; 369:1022-6. [PMID: 18331832 DOI: 10.1016/j.bbrc.2008.02.153] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2008] [Accepted: 02/26/2008] [Indexed: 11/20/2022]
Abstract
Functional Channelrhodopsin-2 (ChR2) overexpression of about 10(4)channels/mum(2) in the plasma membrane of HEK293 cells was studied by patch-clamp and freeze-fracture electron microscopy. Simultaneous electrorotation measurements revealed that ChR2 expression was accompanied by a marked increase of the area-specific membrane capacitance (C(m)). The C(m) increase apparently resulted partly from an enlargement of the size and/or number of microvilli. This is suggested by a relatively large C(m) of 1.15+/-0.08 microF/cm(2) in ChR2-expressing cells measured under isotonic conditions. This value was much higher than that of the control HEK293 cells (0.79+/-0.02 microF/cm(2)). However, even after complete loss of microvilli under strong hypoosmolar conditions (100 mOsm), the ChR2-expressing cells still exhibited a significantly larger C(m) (0.85+/-0.07 microF/cm(2)) as compared to non-expressing control cells (0.70+/-0.03 microF/cm(2)). Therefore, a second mechanism of capacitance increase may involve changes in the membrane permittivity and/or thickness due to the embedded ChR2 proteins.
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Affiliation(s)
- D Zimmermann
- Department of Biophysical Chemistry, Max-Planck-Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany
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Zimmermann D, Kiesel M, Terpitz U, Zhou A, Reuss R, Kraus J, Schenk WA, Bamberg E, Sukhorukov VL. A combined patch-clamp and electrorotation study of the voltage- and frequency-dependent membrane capacitance caused by structurally dissimilar lipophilic anions. J Membr Biol 2008; 221:107-21. [PMID: 18197354 PMCID: PMC2755742 DOI: 10.1007/s00232-007-9090-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2007] [Accepted: 12/13/2007] [Indexed: 11/30/2022]
Abstract
Interactions of structurally dissimilar anionic compounds with the plasma membrane of HEK293 cells were analyzed by patch clamp and electrorotation. The combined approach provides complementary information on the lipophilicity, preferential affinity of the anions to the inner/outer membrane leaflet, adsorption depth and transmembrane mobility. The anionic species studied here included the well-known lipophilic anions dipicrylamine (DPA−), tetraphenylborate (TPB−) and [W2(CO)10(S2CH)]−, the putative lipophilic anion
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\begin{document}$$ {\text{B}}{\left( {{\text{CF}}_{3} } \right)}^{ - }_{4} $$\end{document} and three new heterocyclic W(CO)5 derivatives. All tested anions partitioned strongly into the cell membrane, as indicated by the capacitance increase in patch-clamped cells. The capacitance increment exhibited a bell-shaped dependence on membrane voltage. The midpoint potentials of the maximum capacitance increment were negative, indicating the exclusion of lipophilic anions from the outer membrane leaflet. The adsorption depth of the large organic anions DPA−, TPB− and \documentclass[12pt]{minimal}
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\begin{document}$$ {\text{B}}{\left( {{\text{CF}}_{3} } \right)}^{ - }_{4} $$\end{document} increased and that of W(CO)5 derivatives decreased with increasing concentration of mobile charges. In agreement with the patch-clamp data, electrorotation of cells treated with DPA− and W(CO)5 derivatives revealed a large dispersion of membrane capacitance in the kilohertz to megahertz range due to the translocation of mobile charges. In contrast, in the presence of TPB− and \documentclass[12pt]{minimal}
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\begin{document}$$ {\text{B}}{\left( {{\text{CF}}_{3} } \right)}^{ - }_{4} $$\end{document} no mobile charges could be detected by electrorotation, despite their strong membrane adsorption. Our data suggest that the presence of oxygen atoms in the outer molecular shell is an important factor for the fast translocation ability of lipophilic anions.
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Affiliation(s)
- D Zimmermann
- Department of Biophysical Chemistry, Max-Planck Institute of Biophysics, Max-von-Laue Strasse 3, D-60438, Frankfurt am Main, Germany
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Zimmermann D, Westhoff M, Zimmermann G, Gessner P, Gessner A, Wegner LH, Rokitta M, Ache P, Schneider H, Vásquez JA, Kruck W, Shirley S, Jakob P, Hedrich R, Bentrup FW, Bamberg E, Zimmermann U. Foliar water supply of tall trees: evidence for mucilage-facilitated moisture uptake from the atmosphere and the impact on pressure bomb measurements. Protoplasma 2008; 232:11-34. [PMID: 18176835 DOI: 10.1007/s00709-007-0279-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2007] [Accepted: 06/05/2007] [Indexed: 05/25/2023]
Abstract
The water supply to leaves of 25 to 60 m tall trees (including high-salinity-tolerant ones) was studied. The filling status of the xylem vessels was determined by xylem sap extraction (using jet-discharge, gravity-discharge, and centrifugation) and by (1)H nuclear magnetic resonance imaging of wood pieces. Simultaneously, pressure bomb experiments were performed along the entire trunk of the trees up to a height of 57 m. Clear-cut evidence was found that the balancing pressure (P(b)) values of leafy twigs were dictated by the ambient relative humidity rather than by height. Refilling of xylem vessels of apical leaves (branches) obviously mainly occurred via moisture uptake from the atmosphere. These findings could be traced back to the hydration and rehydration of mucilage layers on the leaf surfaces and/or of epistomatal mucilage plugs. Xylem vessels also contained mucilage. Mucilage formation was apparently enforced by water stress. The observed mucilage-based foliar water uptake and humidity dependency of the P(b) values are at variance with the cohesion-tension theory and with the hypothesis that P(b) measurements yield information about the relationships between xylem pressure gradients and height.
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Affiliation(s)
- D Zimmermann
- Abteilung für Biophysikalische Chemie, Max-Planck-Institut für Biophysik, Frankfurt am Main, Federal Republic of Germany.
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Zimmermann D, Reuss R, Westhoff M, Gessner P, Bauer W, Bamberg E, Bentrup FW, Zimmermann U. A novel, non-invasive, online-monitoring, versatile and easy plant-based probe for measuring leaf water status. J Exp Bot 2008; 59:3157-67. [PMID: 18689442 PMCID: PMC2504341 DOI: 10.1093/jxb/ern171] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2008] [Revised: 05/23/2008] [Accepted: 05/27/2008] [Indexed: 05/18/2023]
Abstract
A high-precision pressure probe is described which allows non-invasive online-monitoring of the water relations of intact leaves. Real-time recording of the leaf water status occurred by data transfer to an Internet server. The leaf patch clamp pressure probe measures the attenuated pressure, P(p), of a leaf patch in response to a constant clamp pressure, P(clamp). P(p) is sensed by a miniaturized silicone pressure sensor integrated into the device. The magnitude of P(p) is dictated by the transfer function of the leaf, T(f), which is a function of leaf patch volume and ultimately of cell turgor pressure, P(c), as shown theoretically. The power function T(f)=f(P(c)) theoretically derived was experimentally confirmed by concomitant P(p) and P(c) measurements on intact leaflets of the liana Tetrastigma voinierianum under greenhouse conditions. Simultaneous P(p) recordings on leaflets up to 10 m height above ground demonstrated that changes in T(f) induced by P(c) changes due to changes of microclimate and/or of the irrigation regime were sensitively reflected in corresponding changes of P(p). Analysis of the data show that transpirational water loss during the morning hours was associated with a transient rise in turgor pressure gradients within the leaflets. Subsequent recovery of turgescence during the afternoon was much faster than the preceding transpiration-induced water loss if the plants were well irrigated. Our data show the enormous potential of the leaf patch clamp pressure probe for leaf water studies including unravelling of the hydraulic communication between neighbouring leaves and over long distances within tall plants (trees).
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Affiliation(s)
- D Zimmermann
- Abteilung für Biophysikalische Chemie, Max-Planck-Institut für Biophysik, Max-von-Laue-Str. 3, D-60439 Frankfurt a. M., Germany.
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21
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Sukhorukov VL, Endter JM, Zimmermann D, Shirakashi R, Fehrmann S, Kiesel M, Reuss R, Becker D, Hedrich R, Bamberg E, Roitsch T, Zimmermann U. Mechanisms of electrically mediated cytosolic Ca2+ transients in aequorin-transformed tobacco cells. Biophys J 2007; 93:3324-37. [PMID: 17675352 PMCID: PMC2025648 DOI: 10.1529/biophysj.107.110783] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2007] [Accepted: 07/10/2007] [Indexed: 11/18/2022] Open
Abstract
Cytosolic Ca(2+) changes induced by electric field pulses of 50-micros duration and 200-800 V/cm strength were monitored by measuring chemiluminescence in aequorin-transformed BY-2 tobacco cells. In Ca(2+)-substituted media, electropulsing led to a very fast initial increase of the cytosolic Ca(2+) concentration reaching a peak value within <100-200 ms. Peaking of [Ca(2+)](cyt) was followed by a biphasic decay due to removal of Ca(2+) (e.g., by binding and/or sequestration in the cytosol). The decay had fast and slow components, characterized by time constants of approximately 0.5 and 3-5 s, respectively. Experiments with various external Ca(2+) concentrations and conductivities showed that the fast decay arises from Ca(2+) fluxes through the plasmalemma, whereas the slow decay must be assigned to Ca(2+) fluxes through the tonoplast. The amplitude of the [Ca(2+)](cyt) transients increased with increasing field strength, whereas the time constants of the decay kinetics remained invariant. Breakdown of the plasmalemma was achieved at a critical field strength of approximately 450 V/cm, whereas breakdown of the tonoplast required approximately 580 V/cm. The above findings could be explained by the transient potential profiles generated across the two membranes in response to an exponentially decaying field pulse. The dielectric data required for calculation of the tonoplast and plasmalemma potentials were derived from electrorotation experiments on isolated vacuolated and evacuolated BY-2 protoplasts. The electrorotation response of vacuolated protoplasts could be described in terms of a three-shell model (i.e., by assuming that the capacitances of tonoplast and plasmalemma are arranged in series). Among other things, the theoretical analysis together with the experimental data show that genetic manipulations of plant cells by electrotransfection or electrofusion must be performed in low-conductivity media to minimize release of vacuolar Ca(2+) and presumably other vacuolar ingredients.
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Affiliation(s)
- V L Sukhorukov
- Lehrstuhl für Biotechnologie, Julius-von-Sachs-Institut für Biowissenschaften, Universität Würzburg, Würzburg, Germany
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22
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Abstract
Proton translocation in the BR mutants D85N, D85T and D85,96N was studied by attachment of purple membranes to planar lipid bilayers. Pump currents in these mutants were measured via capacitive coupling and by use of the appropriate ionophores. All mutants have a reduced pK of their Schiff bases around 8-8.5 in common. At physiological pH, a mixture of chromophores absorbing at 410 nm (deprotonated form) and around 600 nm (protonated form) coexists. Excitation with continuous blue light induces in all three mutants an outwardly directed stationary pump current. These currents are enhanced upon addition of azide in D85N and D85,96N by a factor of 50, but no azide enhancement is observed in D85T. Yellow light alone induces transient inwardly directed currents in the mutants but additional blue light leads to a stationary current with the same direction. All the observed currents are carried by protons, so that the consecutive absorption of a yellow and a blue photon leads to inverted stationary photocurrents by the mutants, as observed with halorhodopsin (HR). A mechanistic model describing the inversion of proton pumping is discussed by the cis-trans, trans-cis isomerization of the retinal and the different proton accessibility of the Schiff base from the extracellular or the cytoplasmic side of the membrane.
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Affiliation(s)
- J Tittor
- Max-Planck-Institut für Biochemie, D-82152 Martinsried, Germany
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23
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Zimmermann D, Terpitz U, Zhou A, Reuss R, Müller K, Sukhorukov VL, Gessner P, Nagel G, Zimmermann U, Bamberg E. Biophysical characterisation of electrofused giant HEK293-cells as a novel electrophysiological expression system. Biochem Biophys Res Commun 2006; 348:673-81. [PMID: 16890205 DOI: 10.1016/j.bbrc.2006.07.112] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2006] [Accepted: 07/20/2006] [Indexed: 11/25/2022]
Abstract
Giant HEK293 cells of 30-65 microm in diameter were produced by three-dimensional multi-cell electrofusion in 75 mOsm sorbitol media. These strong hypotonic conditions facilitated fusion because of the spherical shape and smooth membrane surface of the swollen cells. A regulatory volume decrease (RVD), as observed at higher osmolalities, did not occur at 75 mOsm. In contrast to field-treated, but unfused cells, the increase in volume induced by hypotonic shock was only partly reversible in the case of fused giant cells after their transfer into isotonic medium. The large size of the electrofused cells allowed the study of their electrophysiological properties by application of both whole-cell and giant excised patch-clamp techniques. Recordings on giant cells yielded a value of 1.1+/-0.1 microF/cm2 for the area-specific membrane capacitance. This value was consistent with that of the parental cells. The area-specific conductivity of giant cells (diameter > 50 microm) was found to be between 12.8 and 16.1 microS/cm2, which is in the range of that of the parental cells. Measurements with patch-pipettes containing fluorescein showed uniform dye uptake in the whole-cell configuration, but not in the cell-attached configuration. The diffusion-controlled uniform uptake of the dye into the cell interior excludes internal compartmentalisation. The finding of a homogeneous fusion was also supported by expression of the yellow fluorescent protein YFP (as part of the fusion-protein ChR2-YFP) in giant cells since no plasma-membrane bound YFP-mediated fluorescence was detected in the interior of the electrofused cells. Functional expression and the electrophysiological characterisation of the light-activated cation channel Channelrhodopsin 2 (ChR2) yielded similar results as for parental cells. Most importantly, the giant cells exhibited a comparable expression density of the channel protein in the plasma membrane as observed in parental cells. This demonstrates that electrofused cells can be used as a heterologous expression system.
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Affiliation(s)
- D Zimmermann
- Department of Biophysical Chemistry, Max-Planck-Institute of Biophysics, Max-von-Laue Strasse 3, 60438 Frankfurt am Main, Germany
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Kiesel M, Reuss R, Endter J, Zimmermann D, Zimmermann H, Shirakashi R, Bamberg E, Zimmermann U, Sukhorukov VL. Swelling-activated pathways in human T-lymphocytes studied by cell volumetry and electrorotation. Biophys J 2006; 90:4720-9. [PMID: 16565059 PMCID: PMC1471856 DOI: 10.1529/biophysj.105.078725] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Small organic solutes, including sugar derivatives, amino acids, etc., contribute significantly to the osmoregulation of mammalian cells. The present study explores the mechanisms of swelling-activated membrane permeability for electrolytes and neutral carbohydrates in Jurkat cells. Electrorotation was used to analyze the relationship between the hypotonically induced changes in the electrically accessible surface area of the plasma membrane (probed by the capacitance) and its permeability to the monomeric sugar alcohol sorbitol, the disaccharide trehalose, and electrolyte. Time-resolved capacitance and volumetric measurements were performed in parallel using media of different osmolalities containing either sorbitol or trehalose as the major solute. Under mild hypotonic stress in 200 mOsm sorbitol or trehalose solutions, the cells accomplished regulatory volume decrease by releasing cytosolic electrolytes presumably through pathways activated by the swelling-mediated retraction of microvilli. This is suggested by a rapid decrease of the area-specific membrane capacitance C(m) (microF/cm2). The cell membrane was impermeable to both carbohydrates in 200 mOsm media. Whereas trehalose permeability remained also very poor in 100 mOsm medium, extreme swelling of cells in a strongly hypotonic solution (100 mOsm) led to a dramatic increase in sorbitol permeability as evidenced by regulatory volume decrease inhibition. The different osmotic thresholds for activation of electrolyte release and sorbitol influx suggest the involvement of separate swelling-activated pathways. Whereas the electrolyte efflux seemed to utilize pathways preexisting in the plasma membrane, putative sorbitol channels might be inserted into the membrane from cytosolic vesicles via swelling-mediated exocytosis, as indicated by a substantial increase in the whole-cell capacitance C(C) (pF) in strongly hypotonic solutions.
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Affiliation(s)
- M Kiesel
- Lehrstuhl für Biotechnologie, Universität Würzburg, Biozentrum, Würzburg, Germany
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Abstract
Phototaxis and photophobic responses of green algae are mediated by rhodopsins with microbial type chromophores, i.e. all-trans-retinal in the ground state. The green alga Chlamydomonas reinhardtii was recently completely sequenced and the EST (expressed sequence tag) database was made public. We and others detected overlapping partial cDNA sequences that encode two proteins which we termed channelopsins (Chops). The N-terminal half of chop1 (approximately 300 of 712 amino acids) comprises hypothetical seven-transmembrane segments with sequence similarity to the proton pump bacteriorhodopsin and the chloride pump halorhodopsin. Even though the overall sequence homology is low, several amino acids are conserved that define the retinal-binding site and the H+-transporting network in BR (bacteriorhodopsin). Expression of Chop1, or only the hydrophobic core, in Xenopus laevis oocytes, enriched with retinal, produced a light-gated conductance (maximum at approx. 500 nm), which shows characteristics of a channel [ChR1 (channelrhodopsin-1)] that is selectively permeable for protons. Also ChR2 (737 amino acids) is an ion channel that is switched directly by light and also here the hydrophobic N-terminal half of the protein is sufficient to enable light-sensitive channel activity. The action spectrum is blue-shifted (maximum at approx. 460 nm) with respect to ChR1. In addition to protons, ChR2 is permeable to univalent and bivalent cations. We suggest that ChRs are involved in phototaxis of green algae. We show that heterologous expression of ChR2 is useful to manipulate intracellular pCa or membrane potential of animal cells, simply by illumination.
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Affiliation(s)
- G Nagel
- Max-Planck-Institut für Biophysik, Max-von-Laue-Strasse 3, 60438 Frankfurt, Germany.
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Wolf R, Zimmermann D, Weber M, Feilen P, Ehrhart F, Salinas Jungjohann M, Katsen A, Behringer M, Gessner P, Pliess L, Steinbach A, Spitz J, Vásquez JA, Schneider S, Bamberg E, Weber MM, Zimmermann U, Zimmermann H. Real-time 3-D dark-field microscopy for the validation of the cross-linking process of alginate microcapsules. Biomaterials 2005; 26:6386-93. [PMID: 15913773 DOI: 10.1016/j.biomaterials.2005.04.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2005] [Accepted: 04/05/2005] [Indexed: 11/28/2022]
Abstract
Alginate-based microencapsulation is a promising method for long-term maintenance of cellular and membrane function of the cells and tissue fragments required for in vitro and in vivo biosensors, for tissue engineering and particularly for immunoisolation of non-autologous transplants. Microcapsules of high mechanical strength and optimum permeability can be produced by injection of BaCl2 crystals into alginate droplets before they come into contact with external Ba2+. A key requirement is that the system parameters (number of crystals, speed of the crystal stream etc.) are properly adjusted according to the mannuronic and guluronic acid ratio and the average molecular mass of the alginate as well as to the diameter of the microcapsules. Robust, reliable, rapid and low-cost validation tools are, therefore, needed for assurance of the microcapsule quality. Here, we describe a novel three-dimensional (3-D) dark-field microscopy that allows the real-time measurement of the number and spatial distribution of the injected Ba2+ ions throughout the microcapsules after treatment with sulphate. This novel method requires only a conventional microscope equipped with three polarising filters and a double aperture stop. In contrast to confocal laser scanning microscopy images, peripherally attached BaSO4 precipitates can clearly be distinguished from internal ones. The data also demonstrate that several steps of the alginate gelling process must be improved before such immunoisolation can be used in patients.
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Affiliation(s)
- R Wolf
- Lehrstuhl für Zoologie I, Elektronenmikroskopie, Biozentrum, Universität Würzburg, 97074 Würzburg, Germany
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27
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Zuber D, Krause R, Venturi M, Padan E, Bamberg E, Fendler K. Kinetics of charge translocation in the passive downhill uptake mode of the Na+/H+ antiporter NhaA of Escherichia coli. Biochimica et Biophysica Acta (BBA) - Bioenergetics 2005; 1709:240-50. [PMID: 16139785 DOI: 10.1016/j.bbabio.2005.07.009] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2005] [Revised: 07/26/2005] [Accepted: 07/27/2005] [Indexed: 11/24/2022]
Abstract
The Na+/H+ antiporter NhaA is the main Na+ extrusion system in E. coli. Using direct current measurements combined with a solid supported membrane (SSM), we obtained electrical data of the function of NhaA purified and reconstituted in liposomes. These measurements demonstrate NhaA's electrogenicity, its specificity for Li+ and Na+ and its pronounced pH dependence in the range pH 6.5-8.5. The mutant G338S, in contrast, presents a pH independent profile, as reported previously. A complete right-side-out orientation of the NhaA antiporter within the proteoliposomal membrane was determined using a NhaA-specific antibody based ELISA assay. This allowed for the first time the investigation of NhaA in the passive downhill uptake mode corresponding to the transport of Na+ from the periplasmic to the cytoplasmic side of the membrane. In this mode, the transporter has kinetic properties differing significantly from those of the previously investigated efflux mode. The apparent Km values were 11 mM for Na+ and 7.3 mM for Li+ at basic pH and 180 mM for Na+ and 50 mM for Li+ at neutral pH. The data demonstrate that in the passive downhill uptake mode pH regulation of the carrier affects both apparent Km as well as turnover (Vmax).
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Affiliation(s)
- D Zuber
- Max Planck Institut für Biophysik, Max von Laue Strasse 3, D-60438 Frankfurt/Main, Germany
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28
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Sukhorukov VL, Reuss R, Zimmermann D, Held C, Müller KJ, Kiesel M, Gessner P, Steinbach A, Schenk WA, Bamberg E, Zimmermann U. Surviving High-Intensity Field Pulses: Strategies for Improving Robustness and Performance of Electrotransfection and Electrofusion. J Membr Biol 2005; 206:187-201. [PMID: 16456714 DOI: 10.1007/s00232-005-0791-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2005] [Revised: 09/08/2005] [Indexed: 11/25/2022]
Abstract
Electrotransfection and electrofusion, both widely used in research and medical applications, still have to face a range of problems, including the existence of electroporation-resistant cell types, cell mortality and also great batch-to-batch variations of the transfection and fusion yields. In the present study, a systematic analysis of the parameters critical for the efficiency and robustness of electromanipulation protocols was performed on five mammalian cell types. Factors examined included the sugar composition of hypotonic pulse media (trehalose, sorbitol or inositol), the kinetics of cell volume changes prior to electropulsing, as well as the growth medium additives used for post-pulse cell cultivation. Whereas the disaccharide trehalose generally allowed regulatory volume decrease (RVD), the monomeric sugar alcohols sorbitol and inositol inhibited RVD or even induced secondary swelling. The different volume responses could be explained by the sugar selectivity of volume-sensitive channels (VSC) in the plasma membrane of all tested cell types. Based on the volumetric data, highest transfection and fusion yields were mostly achieved when the target cells were exposed to hypotonicity for about 2 min prior to electropulsing. Longer hypotonic treatment (10-20 min) decreased the yields of viable transfected and hybrid cells due to (1) the cell size reduction upon RVD (trehalose) or (2) the excessive losses of cytosolic electrolytes through VSC (inositol/sorbitol). Doping the plasma membrane with lipophilic anions prevented both cell shrinkage and ion losses (probably due to VSC inhibition), which in turn resulted in increased transfection and fusion efficiencies.
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Affiliation(s)
- V L Sukhorukov
- Lehrstuhl für Biotechnologie, Biozentrum, Universität Würzburg, Am Hubland, Würzburg D-97074, Germany
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29
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Robia CB, Mitteregger G, Aichinger A, Benesch M, Bamberg E. Effect of Testosterone and Oestradiol-17beta on Canine Hair Follicle Culture. J Vet Med Series A 2003; 50:225-9. [PMID: 14567507 DOI: 10.1046/j.1439-0442.2003.00522.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Skin biopsies were taken from four body sites (head, thorax, flank and perineum) of three male entire Beagles and the primary hair follicles were isolated. Culture conditions were established to keep the hair follicles growing for up to 7 days. Additionally, hair follicles were incubated in supplemented medium (containing insulin, transferrin, glutamine and sodium selenite) with or without the addition of testosterone (T) (1, 10 or 100 ng/ml) or oestradiol-17beta (E2beta) (0.01, 0.1 or 1 ng/ml), respectively and the daily growth of hair follicles was measured. In vitro daily growth of hair follicles from the thorax was stimulated by the low concentration of both hormones, but the growth of those from the flank was inhibited by the high concentration of both hormones. Hair follicles from the head were positively influenced by the lowest concentration of T and the medium concentration of E2beta. The daily growth of hair follicles from the perineum was not significantly influenced by either hormone.
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Affiliation(s)
- C B Robia
- Department of Biochemistry, Ludwig Boltzmann Institute of Veterinary Endocrinology, University of Veterinary Medicine, Vienna, Austria
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Bamberg E, Hegemann P, Oesterhelt D. The chromoprotein of halorhodopsin is the light-driven electrogenic chloride pump in Halobacterium halobium. Biochemistry 2002; 23:6216-21. [DOI: 10.1021/bi00320a050] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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31
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Wolf H, Ringsdorf H, Delamarche E, Takami T, Kang H, Michel B, Gerber C, Jaschke M, Butt HJ, Bamberg E. End-Group-Dominated Molecular Order in Self-Assembled Monolayers. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100018a050] [Citation(s) in RCA: 129] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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32
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34
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Abstract
Stress enhances the production of corticosteroids by the adrenal cortex, resulting in the increased excretion of their metabolites in urine and faeces. An intraperitoneal injection of radioactive corticosterone was applied to adult, male Sprague-Dawley rats to monitor the route and delay of excreted metabolites in urine and faeces. Peak concentrations appeared in urine after 3.2 +/- 1.9 h and in faeces after 16.7 +/- 4.3 h. Altogether about 20% of the recovered metabolites were found in urine and about 80% in faeces. Using high-performance liquid chromatography (HPLC), several peaks of radioactive metabolites were found. Some metabolites were detected by enzyme immunoassay (EIA) using two different antibodies (corticosterone, 11beta-OH-aetiocholanolone). There was a marked diurnal variation with low levels of faecal corticosterone metabolites in the evening and higher values in the morning. This diurnal variation was influenced neither by the intraperitoneal injection of isotonic saline nor by ACTH. However, the administration of dexamethasone eliminated the morning peak for 2 days.
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Affiliation(s)
- E Bamberg
- Ludwig Boltzmann-Institut für Veterinärmedizinische Endokrinologie, Universität Wien, Austria.
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35
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Abstract
Electrical measurements on planar lipid bilayers, patch/voltage clamp experiments, and spectroscopic investigations involving a potential sensitive dye are reviewed. These experiments were performed to analyze the kinetics of charge translocation of the Na+,K+-ATPase. High time resolution was achieved by applying caged ATP, voltage-jump, and stopped-flow techniques, respectively. Kinetic parameters and the electrogenicity of the relevant transitions in the Na+,K+-ATPase reaction cycle are discussed.
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Affiliation(s)
- E Bamberg
- Max-Planck-Institut für Biophysik, Frankfurt am Main, Germany.
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36
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Geibel S, Friedrich T, Ormos P, Wood PG, Nagel G, Bamberg E. The voltage-dependent proton pumping in bacteriorhodopsin is characterized by optoelectric behavior. Biophys J 2001; 81:2059-68. [PMID: 11566778 PMCID: PMC1301679 DOI: 10.1016/s0006-3495(01)75855-9] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The light-driven proton pump bacteriorhodopsin (bR) was functionally expressed in Xenopus laevis oocytes and in HEK-293 cells. The latter expression system allowed high time resolution of light-induced current signals. A detailed voltage clamp and patch clamp study was performed to investigate the DeltapH versus Deltapsi dependence of the pump current. The following results were obtained. The current voltage behavior of bR is linear in the measurable range between -160 mV and +60 mV. The pH dependence is less than expected from thermodynamic principles, i.e., one DeltapH unit produces a shift of the apparent reversal potential of 34 mV (and not 58 mV). The M(2)-BR decay shows a significant voltage dependence with time constants changing from 20 ms at +60 mV to 80 ms at -160 mV. The linear I-V curve can be reconstructed by this behavior. However, the slope of the decay rate shows a weaker voltage dependence than the stationary photocurrent, indicating that an additional process must be involved in the voltage dependence of the pump. A slowly decaying M intermediate (decay time > 100 ms) could already be detected at zero voltage by electrical and spectroscopic means. In effect, bR shows optoelectric behavior. The long-lived M can be transferred into the active photocycle by depolarizing voltage pulses. This is experimentally demonstrated by a distinct charge displacement. From the results we conclude that the transport cycle of bR branches via a long-lived M(1)* in a voltage-dependent manner into a nontransporting cycle, where the proton release and uptake occur on the extracellular side.
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Affiliation(s)
- S Geibel
- Max Planck Institut für Biophysik, D-60596 Frankfurt am Main, Germany
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37
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Arndt P, Volk C, Gorboulev V, Budiman T, Popp C, Ulzheimer-Teuber I, Akhoundova A, Koppatz S, Bamberg E, Nagel G, Koepsell H. Interaction of cations, anions, and weak base quinine with rat renal cation transporter rOCT2 compared with rOCT1. Am J Physiol Renal Physiol 2001; 281:F454-68. [PMID: 11502595 DOI: 10.1152/ajprenal.2001.281.3.f454] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The rat organic cation transporter (rOCT)-2 was characterized by electrical and tracer flux measurements compared with rOCT1. By applying choline gradients to voltage-clamped Xenopus oocytes expressing rOCT2, potential-dependent currents could be induced in both directions. Tracer flux measurements with seven organic cations revealed similar Michaelis-Menten constant values for both transporters, with the exception of guanidine. In parallel experiments with rOCT2 and rOCT1, inhibition of tetraethylammonium transport by 12 cations, 2 weak bases, corticosterone, and the anions para-amminohippurate, alpha-ketoglutarate, and probenecid was characterized. The IC(50) values of many inhibitors were similar for both transporters, whereas others were significantly different. Mepiperphenidol and O-methylisoprenaline showed an approximately 70-fold lower and corticosterone a 38-fold higher affinity for rOCT2. With the use of these inhibitors together with previous information on cation transporters, experimental protocols are proposed to dissect out the individual contributions of rOCT2 and rOCT1 in intact proximal tubule preparations. Inhibition experiments at different pH levels strongly suggest that the weak base quinine passively permeates the plasma membrane at physiological pH and inhibits rOCT2 from the intracellular side.
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Affiliation(s)
- P Arndt
- Institute of Anatomy of the Bayerische Julius-Maximilians-Universität, Koellikerstr. 6, 97070 Würzburg, Germany
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38
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Schmies G, Engelhard M, Wood PG, Nagel G, Bamberg E. Electrophysiological characterization of specific interactions between bacterial sensory rhodopsins and their transducers. Proc Natl Acad Sci U S A 2001; 98:1555-9. [PMID: 11171989 PMCID: PMC29295 DOI: 10.1073/pnas.98.4.1555] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The halobacterial phototaxis receptors sensory rhodopsin I and II (SRI, SRII) enable the bacteria to seek optimal light conditions for ion pumping by bacteriorhodopsin and/or halorhodopsin. The incoming signal is transferred across the plasma membrane by means of receptor-specific transducer proteins that bind tightly to their corresponding photoreceptors. To investigate the receptor/transducer interaction, advantage is taken of the observation that both SRI and SRII can function as proton pumps. SRI from Halobacterium salinarum, which triggers the positive phototaxis, the photophobic receptor SRII from Natronobacterium pharaonis (pSRII), as well as the mutant pSRII-F86D were expressed in Xenopus oocytes. Voltage-clamp studies confirm that SRI and pSRII function as light-driven, outwardly directed proton pumps with a much stronger voltage dependence than the ion pumps bacteriorhodopsin and halorhodopsin. Coexpression of SRI and pSRII-F86D with their corresponding transducers suppresses the proton transport, revealing a tight binding and specific interaction of the two proteins. These latter results may be exploited to further analyze the binding interaction of the photoreceptors with their downstream effectors.
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Affiliation(s)
- G Schmies
- Max-Planck-Institut für Molekulare Physiologie, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
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39
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Hattab SA, Kadoom AK, Palme R, Bamberg E. Effect of CRESTAR on estrus synchronization and the relationship between fecal and plasma concentrations of progestagens in buffalo cows. Theriogenology 2000; 54:1007-17. [PMID: 11131319 DOI: 10.1016/s0093-691x(00)00409-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In buffaloes estrus synchronization provides an opportunity for enhanced use of AI; however, changes in hormone secretion during synchronization are poorly understood. The aim of this investigation was to determine if the concentration of progesterone metabolites in feces would correlate with the concentration of progesterone in blood and thus, could be used for noninvasive monitoring of the reproductive status in buffalo cows. Additionally, the influence of a norgestomet-estradiol treatment (CRESTAR-ear implant) was investigated. According to the clinical examination and the progesterone profile in blood samples during the three wks before the treatment, the 17 animals were allotted to 3 groups: 1) CL = presence of corpus luteum throughout the period of 3 wks before the treatment (n = 8); 2) CY = cyclic, corpus luteum present for less than 3 wks (n = 6); and 3) AE = anestrous, with inactive ovaries (n = 3). In the first group, 4 animals started an estrous cycle after implant withdrawal and conceived after natural mating. In the second group one of the cyclic cows showed estrus two d after implant withdrawal, the other 3 had a delayed estrus (12 to 16 d). The two cows which had had inactive ovaries at the beginning but were cyclic before the treatment started, remained cyclic after implant withdrawal but did not become pregnant. The 3 anestrous cows of the third group remained anestrous after the treatment. The progesterone concentration in blood clearly correlated with the concentration of the metabolites in feces. Therefore, this noninvasive method is a valuable tool for determining the luteal status, and such information may be useful for developing estrus synchronization regimens in buffalo cows.
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Affiliation(s)
- S A Hattab
- Theriogenology Department, Faculty of Veterinary Medicine, Alexandria University Edfina, Behira, Egypt
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40
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Abstract
The organic cation transporter 2 (OCT2) is expressed in plasma membranes of kidney and brain. Its transport mechanism and substrates are debated. We studied substrate-induced changes of electrical current with the patch clamp technique after expression of rat OCT2 in oocytes. Activation of current, corresponding to efflux, was observed for small organic cations, e.g. choline. In contrast, the bigger cations quinine and tetrabutylammonium elicited no change in current. However, transport of choline could be inhibited by applying quinine or tetrabutylammonium to the cytoplasmic side. Inhibition of organic cation efflux by quinine was competitive with substrates. Quinine at the inside also inhibited substrate influx from the outside. Current-voltage analysis showed that both maximal turnover and apparent affinity to substrates are voltage-dependent. Substrate-induced currents with organic cations on both membrane sides reversed as predicted from the Nernst potential. Our results clearly identify the electrochemical potential as driving force for transport at neutral pH and exclude an electroneutral H(+)/organic cation(+) exchange. We suggest the existence of an electroneutral organic cation(+) exchange and propose a model for a carrier-type transport mechanism.
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Affiliation(s)
- T Budiman
- Max-Planck-Institute for Biophysics, Kennedyallee 70, D-60596 Frankfurt/M, Germany
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41
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Schrader M, Fendler K, Bamberg E, Gassel M, Epstein W, Altendorf K, Dröse S. Replacement of glycine 232 by aspartic acid in the KdpA subunit broadens the ion specificity of the K(+)-translocating KdpFABC complex. Biophys J 2000; 79:802-13. [PMID: 10920013 PMCID: PMC1300979 DOI: 10.1016/s0006-3495(00)76337-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Replacement of glycine residue 232 with aspartate in the KdpA subunit of the K(+)-translocating KdpFABC complex of Escherichia coli leads to a transport complex that has reduced affinity for K(+) and has lost the ability to discriminate Rb(+) ions (, J. Biol. Chem. 270:6678-6685). This glycine residue is the first in a highly conserved GGG motif that was aligned with the GYG sequence of the selectivity filter (P- or H5-loop) of K(+) channels (, Nature. 371:119-122). Investigations with the purified and reconstituted KdpFABC complex using the potential sensitive fluorescent dye DiSC(3)(5) and the "caged-ATP/planar bilayer method" confirm the altered ion specificity observed in uptake measurements with whole cells. In the absence of cations a transient current was observed in the planar bilayer measurements, a phenomenon that was previously observed with the wild-type enzyme and with another kdpA mutant (A:Q116R) and most likely represents the movement of a protein-fixed charge during a conformational transition. After addition of K(+) or Rb(+), a stationary current could be observed, representing the continuous pumping activity of the KdpFABC complex. In addition, DiSC(3)(5) and planar bilayer measurements indicate that the A:G232D Kdp-ATPase also transports Na(+), Li(+), and H(+) with a reduced rate. Similarities to mutations in the GYG motif of K(+) channels are discussed.
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Affiliation(s)
- M Schrader
- Max-Planck-Institut für Biophysik, D-60596 Frankfurt am Main, Germany
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42
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Pfitzner U, Hoffmeier K, Harrenga A, Kannt A, Michel H, Bamberg E, Richter OM, Ludwig B. Tracing the D-pathway in reconstituted site-directed mutants of cytochrome c oxidase from Paracoccus denitrificans. Biochemistry 2000; 39:6756-62. [PMID: 10841754 DOI: 10.1021/bi992235x] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Heme-copper terminal oxidases use the free energy of oxygen reduction to establish a transmembrane proton gradient. While the molecular mechanism of coupling electron transfer to proton pumping is still under debate, recent structure determinations and mutagenesis studies have provided evidence for two pathways for protons within subunit I of this class of enzymes. Here, we probe the D-pathway by mutagenesis of the cytochrome c oxidase of the bacterium Paracoccus denitrificans; amino acid replacements were selected with the rationale of interfering with the hydrophilic lining of the pathway, in particular its assumed chain of water molecules. Proton pumping was assayed in the reconstituted vesicle system by a stopped-flow spectroscopic approach, allowing a reliable assessment of proton translocation efficiency even at low turnover rates. Several mutations at positions above the cytoplasmic pathway entrance (Asn 131, Asn 199) and at the periplasmic exit region (Asp 399) led to complete inhibition of proton pumping; one of these mutants, N131D, exhibited an ideal decoupled phenotype, with a turnover comparable to that of the wild-type enzyme. Since sets of mutations in other positions along the presumed course of the pathway showed normal proton translocation stoichiometries, we conclude that the D-pathway is too wide in most areas above positions 131/199 to be disturbed by single amino acid replacements.
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Affiliation(s)
- U Pfitzner
- Molekulare Genetik, Institut f]ur Biochemie, Biozentrum, Johann Wolfgang Goethe-Universit]at, Marie-Curie-Strasse 9, D-60439 Frankfurt, Germany
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43
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Ruitenberg M, Kannt A, Bamberg E, Ludwig B, Michel H, Fendler K. Single-electron reduction of the oxidized state is coupled to proton uptake via the K pathway in Paracoccus denitrificans cytochrome c oxidase. Proc Natl Acad Sci U S A 2000; 97:4632-6. [PMID: 10781069 PMCID: PMC18284 DOI: 10.1073/pnas.080079097] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The reductive part of the catalytic cycle of cytochrome c oxidase from Paracoccus denitrificans was examined by using time-resolved potential measurements on black lipid membranes. Proteoliposomes were adsorbed to the black lipid membranes and Ru(II)(2, 2'-bipyridyl)(3)(2+) was used as photoreductant to measure flash-induced membrane potential generation. Single-electron reduction of the oxidized wild-type cytochrome c oxidase reveals two phases of membrane potential generation (tau(1) approximately 20 micros and tau(2) approximately 175 micros) at pH 7.4. The fast phase is not sensitive to cyanide and is assigned to electron transfer from Cu(A) to heme a. The slower phase is inhibited completely by cyanide and shows a kinetic deuterium isotope effect by a factor of 2-3. Although two enzyme variants mutated in the so-called D pathway of proton transfer (D124N and E278Q) show the same time constants and relative amplitudes as the wild-type enzyme, in the K pathway variant K354M, tau(2) is increased to 900 micros. This result suggests uptake of a proton through the K pathway during the transition from the oxidized to the one-electron reduced state. After the second laser flash under anaerobic conditions, a third electrogenic phase with a time constant of approximately 1 ms appears. The amplitude of this phase grows with increasing flash number. We explain this growth by injection of a second electron into the single-electron reduced enzyme. On multiple flashes, both D pathway mutants behave differently compared with the wild type and two additional slow phases of tau(3) approximately 2 ms and tau(4) approximately 15 ms are observed. These results suggest that the D pathway is involved in proton transfer coupled to the uptake of the second electron.
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Affiliation(s)
- M Ruitenberg
- Max-Planck-Institute of Biophysics, Department of Biophysical Chemistry, Kennedyallee 70, 60596 Frankfurt/Main, Germany
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44
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Sauer GA, Nagel G, Koepsell H, Bamberg E, Hartung K. Voltage and substrate dependence of the inverse transport mode of the rabbit Na(+)/glucose cotransporter (SGLT1). FEBS Lett 2000; 469:98-100. [PMID: 10708764 DOI: 10.1016/s0014-5793(00)01255-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Properties of the cytoplasmic binding sites of the rabbit Na(+)/glucose cotransporter, SGLT1, expressed in Xenopus oocytes were investigated using the giant excised patch clamp technique. Voltage and substrate dependence of the outward cotransport were studied using alpha-methyl D-glucopyranoside (alphaMDG) as a substrate. The apparent affinity for alphaMDG depends on the cytoplasmic Na(+) concentration and voltage. At 0 mV the K(M) for alphaMDG is 7 mM at 110 mM Na(+) and 31 mM at 10 mM Na(+). The apparent affinity for alphaMDG and Na(+) is voltage dependent and increases at positive potentials. At 0 mV holding potential the outward current is half-maximal at about 70 mM. The results show that SGLT1 can mediate sugar transport out of the cell under appropriate concentration and voltage conditions, but under physiological conditions this transport is highly improbable due to the low affinity for sugar.
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Affiliation(s)
- G A Sauer
- Max-Planck-Institut für Biophysik, Kennedyallee 70, D-60596, Frankfurt, Germany
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45
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Abstract
Increased production of glucocorticoids by the adrenal cortex is found in mammals under stress. As cortisol itself is absent in the faeces, an enzyme immunoassay (11-oxoaetiocholanolone) measuring 11,17-dioxoandrostanes has already been established to measure faecal cortisol metabolites in ruminants for non-invasive monitoring of adrenocortical activity. The aim of this study was to establish route and delay of excretion of glucocorticoids in hares and to determine whether a cortisol-, corticosterone- or this new enzyme immunoassay is best suited to detect faecal glucocorticoid metabolites. In the first experiment radioactive-labelled glucocorticoids (14C-cortisol and 3H-corticosterone) were administered intravenously to two groups of three hares in metabolic cages. All voided urine and faecal samples were collected for 4 days. Metabolites of both steroids were found predominantly in the urine (91 +/- 4%). Peak concentrations were observed in the first urinary sample following infusion (13 +/- 6 h) and in the faeces with a delay of about 1 day (23 +/- 7 h). Most of the radioactivity was not extractable with diethylether, indicating that the metabolites excreted in urine and faeces are mainly conjugated or polar unconjugated ones. This was confirmed by reverse-phase high-performance liquid chromatography separations of the metabolites, which also revealed marked differences concerning the metabolism of the two glucocorticoids injected. Compared with the cortisol and the corticosterone enzyme immunoassay, only the group-specific enzyme immunoassay for 11,17-dioxoandrostanes detected high quantities of immunoreactive metabolites. In a second experiment hares (n = 20) were stressed by rousing them three times (5 min, 10 min and another 5 min) with a 20-min break in-between. Faecal samples were collected 2 days before until 4 days after stress and analysed using the 11-oxoaetiocholanolone enzyme immunoassay. After stress significantly (P < 0.001) increased 11,17-dioxoandrostane concentrations were found. Based on these results, measuring 11,17-dioxoandrostanes in faeces enables non-invasive monitoring of disturbances in hares and thus provides a tool for field investigations elucidating the role of stress in hare populations.
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Affiliation(s)
- A Teskey-Gerstl
- Institute of Biochemistry, University of Veterinary Medicine, Vienna, Austria
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46
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Schmies G, Lüttenberg B, Chizhov I, Engelhard M, Becker A, Bamberg E. Sensory rhodopsin II from the haloalkaliphilic natronobacterium pharaonis: light-activated proton transfer reactions. Biophys J 2000; 78:967-76. [PMID: 10653809 PMCID: PMC1300699 DOI: 10.1016/s0006-3495(00)76654-9] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
In the present work the light-activated proton transfer reactions of sensory rhodopsin II from Natronobacterium pharaonis (pSRII) and those of the channel-mutants D75N-pSRII and F86D-pSRII are investigated using flash photolysis and black lipid membrane (BLM) techniques. Whereas the photocycle of the F86D-pSRII mutant is quite similar to that of the wild-type protein, the photocycle of D75N-pSRII consists of only two intermediates. The addition of external proton donors such as azide, or in the case of F86D-pSRII, imidazole, accelerates the reprotonation of the Schiff base, but not the turnover. The electrical measurements prove that pSRII and F86D-pSRII can function as outwardly directed proton pumps, whereas the mutation in the extracellular channel (D75N-pSRII) leads to an inwardly directed transient current. The almost negligible size of the photostationary current is explained by the long-lasting photocycle of about a second. Although the M decay, but not the photocycle turnover, of pSRII and F86D-pSRII is accelerated by the addition of azide, the photostationary current is considerably increased. It is discussed that in a two-photon process a late intermediate (N- and/or O-like species) is photoconverted back to the original resting state; thereby the long photocycle is cut short, giving rise to the large increase of the photostationary current. The results presented in this work indicate that the function to generate ion gradients across membranes is a general property of archaeal rhodopsins.
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Affiliation(s)
- G Schmies
- Max-Planck-Institut für Molekulare Physiologie, D-44227 Dortmund, Germany
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47
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Abstract
The electrogenic transport of ATP and ADP by the mitochondrial ADP/ATP carrier (AAC) was investigated by recording transient currents with two different techniques for performing concentration jump experiments: 1) the fast fluid injection method: AAC-containing proteoliposomes were adsorbed to a solid supported membrane (SSM), and the carrier was activated via ATP or ADP concentration jumps. 2) BLM (black lipid membrane) technique: proteoliposomes were adsorbed to a planar lipid bilayer, while the carrier was activated via the photolysis of caged ATP or caged ADP with a UV laser pulse. Two transport modes of the AAC were investigated, ATP(ex)-0(in) and ADP(ex)-0(in). Liposomes not loaded with nucleotides allowed half-cycles of the ADP/ATP exchange to be studied. Under these conditions the AAC transports ADP and ATP electrogenically. Mg(2+) inhibits the nucleotide transport, and the specific inhibitors carboxyatractylate (CAT) and bongkrekate (BKA) prevent the binding of the substrate. The evaluation of the transient currents yielded rate constants of 160 s(-1) for ATP and >/=400 s(-1) for ADP translocation. The function of the carrier is approximately symmetrical, i.e., the kinetic properties are similar in the inside-out and right-side-out orientations. The assumption from previous investigations, that the deprotonated nucleotides are exclusively transported by the AAC, is supported by further experimental evidence. In addition, caged ATP and caged ADP bind to the carrier with similar affinities as the free nucleotides. An inhibitory effect of anions (200-300 mM) was observed, which can be explained as a competitive effect at the binding site. The results are summarized in a transport model.
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Affiliation(s)
- T Gropp
- Max-Planck-Institut für Biophysik, 60596 Frankfurt, Germany
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48
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Andersen OS, Apell HJ, Bamberg E, Busath DD, Koeppe RE, Sigworth FJ, Szabo G, Urry DW, Woolley A. Gramicidin channel controversy--the structure in a lipid environment. Nat Struct Biol 1999; 6:609; discussion 611-2. [PMID: 10404209 DOI: 10.1038/10648] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- O S Andersen
- Department of Physiology and Biophysics, Weill Medical College of Cornell University, New York, NY 10021, USA
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49
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Fendler K, Dröse S, Epstein W, Bamberg E, Altendorf K. The Kdp-ATPase of Escherichia coli mediates an ATP-dependent, K+-independent electrogenic partial reaction. Biochemistry 1999; 38:1850-6. [PMID: 10026265 DOI: 10.1021/bi982238u] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Charge transport by the K+ transporting Kdp-ATPase from Escherichia coli was investigated using planar lipid membranes to which liposomes reconstituted with the enzyme were adsorbed. To study reactions in the absence of K+, given some contamination of solutions with K+, we used a mutant of Kdp whose affinity for K+ was 6 mM instead of the wild-type whose affinity is 2 microM. Upon rapid release of ATP from caged ATP, a transient current occurred in the absence of K+. In the presence of K+, a stationary current was seen. On the basis of their structural similarity, we propose a kinetic model for the Kdp-ATPase analogous to that of the Na+K+-ATPase. In this model, the first, K+-independent step is electrogenic and corresponds to the outward transport of a negative charge. The second, K+-translocating step is probably also electrogenic and corresponds to transport of positive charge to the intracellular side of the protein.
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Affiliation(s)
- K Fendler
- Max-Planck-Institut für Biophysik, Frankfurt/M, Germany
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50
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Pintschovius J, Fendler K, Bamberg E. Charge translocation by the Na+/K+-ATPase investigated on solid supported membranes: cytoplasmic cation binding and release. Biophys J 1999; 76:827-36. [PMID: 9929484 PMCID: PMC1300084 DOI: 10.1016/s0006-3495(99)77246-2] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
In the preceding publication (. Biophys. J. 76:000-000) a new technique was described that was able to produce concentration jumps of arbitrary ion species at the surface of a solid supported membrane (SSM). This technique can be used to investigate the kinetics of ion translocating proteins adsorbed to the SSM. Charge translocation of the Na+/K+-ATPase in the presence of ATP was investigated. Here we describe experiments carried out with membrane fragments containing Na+/K+-ATPase from pig kidney and in the absence of ATP. Electrical currents are measured after rapid addition of Na+. We demonstrate that these currents can be explained only by a cation binding process on the cytoplasmic side, most probably to the cytoplasmic cation binding site of the Na+/K+-ATPase. An electrogenic reaction of the protein was observed only with Na+, but not with other monovalent cations (K+, Li+, Rb+, Cs+). Using Na+ activation of the enzyme after preincubation with K+ we also investigated the K+-dependent half-cycle of the Na+/K+-ATPase. A rate constant for K+ translocation in the absence of ATP of 0.2-0.3 s-1 was determined. In addition, these experiments show that K+ deocclusion, and cytoplasmic K+ release are electroneutral.
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Affiliation(s)
- J Pintschovius
- Max-Planck-Institut für Biophysik, D-60596 Frankfurt/Main, Germany
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