1
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Sure F, Bertog M, Afonso S, Diakov A, Rinke R, Madej MG, Wittmann S, Gramberg T, Korbmacher C, Ilyaskin AV. Transmembrane serine protease 2 (TMPRSS2) proteolytically activates the epithelial sodium channel (ENaC) by cleaving the channel's γ-subunit. J Biol Chem 2022; 298:102004. [PMID: 35504352 PMCID: PMC9163703 DOI: 10.1016/j.jbc.2022.102004] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 04/21/2022] [Accepted: 04/27/2022] [Indexed: 01/09/2023] Open
Abstract
The epithelial sodium channel (ENaC) is a heterotrimer consisting of α-, β-, and γ-subunits. Channel activation requires proteolytic release of inhibitory tracts from the extracellular domains of α-ENaC and γ-ENaC; however, the proteases involved in the removal of the γ-inhibitory tract remain unclear. In several epithelial tissues, ENaC is coexpressed with the transmembrane serine protease 2 (TMPRSS2). Here, we explored the effect of human TMPRSS2 on human αβγ-ENaC heterologously expressed in Xenopus laevis oocytes. We found that coexpression of TMPRSS2 stimulated ENaC-mediated whole-cell currents by approximately threefold, likely because of an increase in average channel open probability. Furthermore, TMPRSS2-dependent ENaC stimulation was not observed using a catalytically inactive TMPRSS2 mutant and was associated with fully cleaved γ-ENaC in the intracellular and cell surface protein fractions. This stimulatory effect of TMPRSS2 on ENaC was partially preserved when inhibiting its proteolytic activity at the cell surface using aprotinin but was abolished when the γ-inhibitory tract remained attached to its binding site following introduction of two cysteine residues (S155C–Q426C) to form a disulfide bridge. In addition, computer simulations and site-directed mutagenesis experiments indicated that TMPRSS2 can cleave γ-ENaC at sites both proximal and distal to the γ-inhibitory tract. This suggests a dual role of TMPRSS2 in the proteolytic release of the γ-inhibitory tract. Finally, we demonstrated that TMPRSS2 knockdown in cultured human airway epithelial cells (H441) reduced baseline proteolytic activation of endogenously expressed ENaC. Thus, we conclude that TMPRSS2 is likely to contribute to proteolytic ENaC activation in epithelial tissues in vivo.
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Affiliation(s)
- Florian Sure
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Institute of Cellular and Molecular Physiology, Erlangen, Germany
| | - Marko Bertog
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Institute of Cellular and Molecular Physiology, Erlangen, Germany
| | - Sara Afonso
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Institute of Cellular and Molecular Physiology, Erlangen, Germany
| | - Alexei Diakov
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Institute of Cellular and Molecular Physiology, Erlangen, Germany
| | - Ralf Rinke
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Institute of Cellular and Molecular Physiology, Erlangen, Germany
| | - M Gregor Madej
- Department of Biophysics II/Structural Biology, University of Regensburg, Regensburg, Germany
| | - Sabine Wittmann
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Universitätsklinikum Erlangen, Institute of Clinical and Molecular Virology, Erlangen, Germany
| | - Thomas Gramberg
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Universitätsklinikum Erlangen, Institute of Clinical and Molecular Virology, Erlangen, Germany
| | - Christoph Korbmacher
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Institute of Cellular and Molecular Physiology, Erlangen, Germany.
| | - Alexandr V Ilyaskin
- Friedrich-Alexander-Universität Erlangen-Nürnberg, Institute of Cellular and Molecular Physiology, Erlangen, Germany
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2
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Bazzone A, Tesmer L, Kurt D, Kaback HR, Fendler K, Madej MG. Investigation of sugar binding kinetics of the E. coli sugar/H + symporter XylE using solid supported membrane-based electrophysiology. J Biol Chem 2021; 298:101505. [PMID: 34929170 PMCID: PMC8784342 DOI: 10.1016/j.jbc.2021.101505] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 12/11/2021] [Accepted: 12/13/2021] [Indexed: 12/19/2022] Open
Abstract
Bacterial transporters are difficult to study using conventional electrophysiology because of their low transport rates and the small size of bacterial cells. Here, we applied solid-supported membrane–based electrophysiology to derive kinetic parameters of sugar translocation by the Escherichia coli xylose permease (XylE), including functionally relevant mutants. Many aspects of the fucose permease (FucP) and lactose permease (LacY) have also been investigated, which allow for more comprehensive conclusions regarding the mechanism of sugar translocation by transporters of the major facilitator superfamily. In all three of these symporters, we observed sugar binding and transport in real time to determine KM, Vmax, KD, and kobs values for different sugar substrates. KD and kobs values were attainable because of a conserved sugar-induced electrogenic conformational transition within these transporters. We also analyzed interactions between the residues in the available X-ray sugar/H+ symporter structures obtained with different bound sugars. We found that different sugars induce different conformational states, possibly correlating with different charge displacements in the electrophysiological assay upon sugar binding. Finally, we found that mutations in XylE altered the kinetics of glucose binding and transport, as Q175 and L297 are necessary for uncoupling H+ and d-glucose translocation. Based on the rates for the electrogenic conformational transition upon sugar binding (>300 s−1) and for sugar translocation (2 s−1 − 30 s−1 for different substrates), we propose a multiple-step mechanism and postulate an energy profile for sugar translocation. We also suggest a mechanism by which d-glucose can act as an inhibitor for XylE.
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Affiliation(s)
- Andre Bazzone
- Max-Planck-Institute of Biophysics, Department of Biophysical Chemistry in Frankfurt/M, Germany
| | - Laura Tesmer
- Max-Planck-Institute of Biophysics, Department of Biophysical Chemistry in Frankfurt/M, Germany
| | - Derya Kurt
- Max-Planck-Institute of Biophysics, Department of Biophysical Chemistry in Frankfurt/M, Germany
| | - H Ronald Kaback
- University of California, Department of Physiology and Department of Microbiology, Immunology, Molecular Genetics, Molecular Biology Institute in Los Angeles CA, USA
| | - Klaus Fendler
- Max-Planck-Institute of Biophysics, Department of Biophysical Chemistry in Frankfurt/M, Germany
| | - M Gregor Madej
- Institute of Biophysics and Biophysical Chemistry, Department of Structural Biology, University of Regensburg, Universitätsstr. 31, 95053 Regensburg, Germany; Institute of Biophysics, Department of Structural Biology, Saarland University, Center of Human and Molecular Biology, Building 60, 66421 Homburg, Germany
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3
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Grosch M, Brunner K, Ilyaskin AV, Schober M, Staudner T, Schmied D, Stumpp T, Schmidt KN, Madej MG, Pessoa TD, Othmen H, Kubitza M, Osten L, de Vries U, Mair MM, Somlo S, Moser M, Kunzelmann K, Ziegler C, Haerteis S, Korbmacher C, Witzgall R. A polycystin-2 protein with modified channel properties leads to an increased diameter of renal tubules and to renal cysts. J Cell Sci 2021; 134:271186. [PMID: 34345895 PMCID: PMC8435292 DOI: 10.1242/jcs.259013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [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: 06/09/2021] [Accepted: 07/22/2021] [Indexed: 01/14/2023] Open
Abstract
Mutations in the PKD2 gene cause autosomal-dominant polycystic kidney disease but the physiological role of polycystin-2, the protein product of PKD2, remains elusive. Polycystin-2 belongs to the transient receptor potential (TRP) family of non-selective cation channels. To test the hypothesis that altered ion channel properties of polycystin-2 compromise its putative role in a control circuit controlling lumen formation of renal tubular structures, we generated a mouse model in which we exchanged the pore loop of polycystin-2 with that of the closely related cation channel polycystin-2L1 (encoded by PKD2L1), thereby creating the protein polycystin-2poreL1. Functional characterization of this mutant channel in Xenopus laevis oocytes demonstrated that its electrophysiological properties differed from those of polycystin-2 and instead resembled the properties of polycystin-2L1, in particular regarding its permeability for Ca2+ ions. Homology modeling of the ion translocation pathway of polycystin-2poreL1 argues for a wider pore in polycystin-2poreL1 than in polycystin-2. In Pkd2poreL1 knock-in mice in which the endogenous polycystin-2 protein was replaced by polycystin-2poreL1 the diameter of collecting ducts was increased and collecting duct cysts developed in a strain-dependent fashion. Summary: Replacement of the pore region of polycystin-2 with that of polycystin-2L1 results in wider renal tubules and polycystic kidney disease, thus demonstrating the essential function of its ion channel properties.
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Affiliation(s)
- Melanie Grosch
- Institute for Molecular and Cellular Anatomy, University of Regensburg, 93053 Regensburg, Germany
| | - Katrin Brunner
- Institute for Molecular and Cellular Anatomy, University of Regensburg, 93053 Regensburg, Germany
| | - Alexandr V Ilyaskin
- Institute of Cellular and Molecular Physiology, Friedrich-Alexander University of Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Michael Schober
- Institute for Molecular and Cellular Anatomy, University of Regensburg, 93053 Regensburg, Germany
| | - Tobias Staudner
- Institute of Cellular and Molecular Physiology, Friedrich-Alexander University of Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Denise Schmied
- Institute for Molecular and Cellular Anatomy, University of Regensburg, 93053 Regensburg, Germany
| | - Tina Stumpp
- Institute for Molecular and Cellular Anatomy, University of Regensburg, 93053 Regensburg, Germany
| | - Kerstin N Schmidt
- Institute for Molecular and Cellular Anatomy, University of Regensburg, 93053 Regensburg, Germany
| | - M Gregor Madej
- Department of Biophysics, University of Regensburg, 93053 Regensburg, Germany
| | - Thaissa D Pessoa
- Institute of Cellular and Molecular Physiology, Friedrich-Alexander University of Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Helga Othmen
- Institute for Molecular and Cellular Anatomy, University of Regensburg, 93053 Regensburg, Germany
| | - Marion Kubitza
- Institute for Molecular and Cellular Anatomy, University of Regensburg, 93053 Regensburg, Germany
| | - Larissa Osten
- Institute for Molecular and Cellular Anatomy, University of Regensburg, 93053 Regensburg, Germany
| | - Uwe de Vries
- Institute for Molecular and Cellular Anatomy, University of Regensburg, 93053 Regensburg, Germany
| | - Magdalena M Mair
- Faculty of Biology and Preclinical Medicine, University of Regensburg, 93053 Regensburg, Germany
| | - Stefan Somlo
- Departments of Medicine and Genetics, Yale University, New Haven, CT 06520, USA
| | - Markus Moser
- Institute of Experimental Hematology, Technical University of Munich, 81675 Munich, Germany
| | - Karl Kunzelmann
- Department of Physiology, University of Regensburg, 93053 Regensburg, Germany
| | - Christine Ziegler
- Department of Biophysics, University of Regensburg, 93053 Regensburg, Germany
| | - Silke Haerteis
- Institute for Molecular and Cellular Anatomy, University of Regensburg, 93053 Regensburg, Germany
| | - Christoph Korbmacher
- Institute of Cellular and Molecular Physiology, Friedrich-Alexander University of Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Ralph Witzgall
- Institute for Molecular and Cellular Anatomy, University of Regensburg, 93053 Regensburg, Germany
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4
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Grünberger F, Reichelt R, Waege I, Ned V, Bronner K, Kaljanac M, Weber N, El Ahmad Z, Knauss L, Madej MG, Ziegler C, Grohmann D, Hausner W. CopR, a Global Regulator of Transcription to Maintain Copper Homeostasis in Pyrococcus furiosus. Front Microbiol 2021; 11:613532. [PMID: 33505379 PMCID: PMC7830388 DOI: 10.3389/fmicb.2020.613532] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 12/09/2020] [Indexed: 11/24/2022] Open
Abstract
Although copper is in many cases an essential micronutrient for cellular life, higher concentrations are toxic. Therefore, all living cells have developed strategies to maintain copper homeostasis. In this manuscript, we have analyzed the transcriptome-wide response of Pyrococcus furiosus to increased copper concentrations and described the essential role of the putative copper-sensing metalloregulator CopR in the detoxification process. To this end, we employed biochemical and biophysical methods to characterize the role of CopR. Additionally, a copR knockout strain revealed an amplified sensitivity in comparison to the parental strain towards increased copper levels, which designates an essential role of CopR for copper homeostasis. To learn more about the CopR-regulated gene network, we performed differential gene expression and ChIP-seq analysis under normal and 20 μM copper-shock conditions. By integrating the transcriptome and genome-wide binding data, we found that CopR binds to the upstream regions of many copper-induced genes. Negative-stain transmission electron microscopy and 2D class averaging revealed an octameric assembly formed from a tetramer of dimers for CopR, similar to published crystal structures from the Lrp family. In conclusion, we propose a model for CopR-regulated transcription and highlight the regulatory network that enables Pyrococcus to respond to increased copper concentrations.
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Affiliation(s)
- Felix Grünberger
- Institute of Microbiology and Archaea Centre, University of Regensburg, Regensburg, Germany
| | - Robert Reichelt
- Institute of Microbiology and Archaea Centre, University of Regensburg, Regensburg, Germany
| | - Ingrid Waege
- Institute of Microbiology and Archaea Centre, University of Regensburg, Regensburg, Germany
| | - Verena Ned
- Institute of Microbiology and Archaea Centre, University of Regensburg, Regensburg, Germany
| | - Korbinian Bronner
- Institute of Microbiology and Archaea Centre, University of Regensburg, Regensburg, Germany
| | - Marcell Kaljanac
- Department of Structural Biology, Institute of Biophysics and Physical Biochemistry, University of Regensburg, Regensburg, Germany
| | - Nina Weber
- Institute of Microbiology and Archaea Centre, University of Regensburg, Regensburg, Germany
| | - Zubeir El Ahmad
- Institute of Microbiology and Archaea Centre, University of Regensburg, Regensburg, Germany
| | - Lena Knauss
- Institute of Microbiology and Archaea Centre, University of Regensburg, Regensburg, Germany
| | - M. Gregor Madej
- Department of Structural Biology, Institute of Biophysics and Physical Biochemistry, University of Regensburg, Regensburg, Germany
| | - Christine Ziegler
- Department of Structural Biology, Institute of Biophysics and Physical Biochemistry, University of Regensburg, Regensburg, Germany
| | - Dina Grohmann
- Institute of Microbiology and Archaea Centre, University of Regensburg, Regensburg, Germany
| | - Winfried Hausner
- Institute of Microbiology and Archaea Centre, University of Regensburg, Regensburg, Germany
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5
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Seica AFS, Iancu CV, Pfeilschifter B, Madej MG, Choe JY, Hellwig P. Asp 22 drives the protonation state of the Staphylococcus epidermidis glucose/H + symporter. J Biol Chem 2020; 295:15253-15261. [PMID: 32859752 DOI: 10.1074/jbc.ra120.014069] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 08/26/2020] [Indexed: 12/24/2022] Open
Abstract
The Staphylococcus epidermidis glucose/H+ symporter (GlcPSe) is a membrane transporter highly specific for glucose and a homolog of the human glucose transporters (GLUT, SLC2 family). Most GLUTs and their bacterial counterparts differ in the transport mechanism, adopting uniport and sugar/H+ symport, respectively. Unlike other bacterial GLUT homologs (for example, XylE), GlcPSe has a loose H+/sugar coupling. Asp22 is part of the proton-binding site of GlcPSe and crucial for the glucose/H+ co-transport mechanism. To determine how pH variations affect the proton site and the transporter, we performed surface-enhanced IR absorption spectroscopy on the immobilized GlcPSe We found that Asp22 has a pKa of 8.5 ± 0.1, a value consistent with that determined previously for glucose transport, confirming the central role of this residue for the transport mechanism of GlcPSe A neutral replacement of the negatively charged Asp22 led to positive charge displacements over the entire pH range, suggesting that the polarity change of the WT reflects the protonation state of Asp22 We expected that the substitution of the residue Ile105 for a serine, located within hydrogen-bonding distance to Asp22, would change the microenvironment, but the pKa of Asp22 corresponded to that of the WT. A167E mutation, selected in analogy to the XylE, introduced an additional protonatable site and perturbed the protonation state of Asp22, with the latter now exhibiting a pKa of 6.4. These studies confirm that Asp22 is the proton-binding residue in GlcPSe and show that charged residues in its vicinity affect the pKa of glucose/H+ symport.
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Affiliation(s)
- Ana Filipa Santos Seica
- Laboratoire de Bioélectrochimie et Spectroscopie, UMR 7140, CMC, Université de Strasbourg CNRS, Strasbourg, France
| | - Cristina V Iancu
- Department of Chemistry, East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, North Carolina, USA
| | - Benedikt Pfeilschifter
- University of Regensburg, Institute of Biophysics and Physical Biochemistry, Regensburg, Germany
| | - M Gregor Madej
- University of Regensburg, Institute of Biophysics and Physical Biochemistry, Regensburg, Germany
| | - Jun-Yong Choe
- Department of Chemistry, East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, North Carolina, USA; Department of Biochemistry and Molecular Biology, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, USA.
| | - Petra Hellwig
- Laboratoire de Bioélectrochimie et Spectroscopie, UMR 7140, CMC, Université de Strasbourg CNRS, Strasbourg, France
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6
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Madej MG, Ziegler CM. Dawning of a new era in TRP channel structural biology by cryo-electron microscopy. Pflugers Arch 2018; 470:213-225. [PMID: 29344776 DOI: 10.1007/s00424-018-2107-2] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Accepted: 01/03/2018] [Indexed: 12/20/2022]
Abstract
Cryo-electron microscopy (cryo-EM) permits the determination of atomic protein structures by averaging large numbers of individual projection images recorded at cryogenic temperatures-a method termed single-particle analysis. The cryo-preservation traps proteins within a thin glass-like ice layer, making literally a freeze image of proteins in solution. Projections of randomly adopted orientations are merged to reconstruct a 3D density map. While atomic resolution for highly symmetric viruses was achieved already in 2009, the development of new sensitive and fast electron detectors has enabled cryo-EM for smaller and asymmetrical proteins including fragile membrane proteins. As one of the most important structural biology methods at present, cryo-EM was awarded in October 2017 with the Nobel Prize in Chemistry. The molecular understanding of Transient-Receptor-Potential (TRP) channels has been boosted tremendously by cryo-EM single-particle analysis. Several near-atomic and atomic structures gave important mechanistic insights, e.g., into ion permeation and selectivity, gating, as well as into the activation of this enigmatic and medically important membrane protein family by various chemical and physical stimuli. Lastly, these structures have set the starting point for the rational design of TRP channel-targeted therapeutics to counteract life-threatening channelopathies. Here, we attempt a brief introduction to the method, review the latest advances in cryo-EM structure determination of TRP channels, and discuss molecular insights into the channel function based on the wealth of TRP channel cryo-EM structures.
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Affiliation(s)
- M Gregor Madej
- Department of Structural Biology, Institute of Biophysics and Physical Biochemistry, University of Regensburg, Universitätsstrasse 31, D-93053, Regensburg, Germany
| | - Christine M Ziegler
- Department of Structural Biology, Institute of Biophysics and Physical Biochemistry, University of Regensburg, Universitätsstrasse 31, D-93053, Regensburg, Germany.
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7
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Bazzone A, Zabadne AJ, Salisowski A, Madej MG, Fendler K. A Loose Relationship: Incomplete H +/Sugar Coupling in the MFS Sugar Transporter GlcP. Biophys J 2018; 113:2736-2749. [PMID: 29262366 PMCID: PMC5770559 DOI: 10.1016/j.bpj.2017.09.038] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [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: 08/01/2017] [Revised: 09/11/2017] [Accepted: 09/29/2017] [Indexed: 11/26/2022] Open
Abstract
The glucose transporter from Staphylococcus epidermidis, GlcPSe, is a homolog of the human GLUT sugar transporters of the major facilitator superfamily. Together with the xylose transporter from Escherichia coli, XylEEc, the other prominent prokaryotic GLUT homolog, GlcPSe, is equipped with a conserved proton-binding site arguing for an electrogenic transport mode. However, the electrophysiological analysis of GlcPSe presented here reveals important differences between the two GLUT homologs. GlcPSe, unlike XylEEc, does not perform steady-state electrogenic transport at symmetrical pH conditions. Furthermore, when a pH gradient is applied, partially uncoupled transport modes can be generated. In contrast to other bacterial sugar transporters analyzed so far, in GlcPSe sugar binding, translocation and release are also accomplished by the deprotonated transporter. Based on these experimental results, we conclude that coupling of sugar and H+ transport is incomplete in GlcPSe. To verify the viability of the observed partially coupled GlcPSe transport modes, we propose a universal eight-state kinetic model in which any degree of coupling is realized and H+/sugar symport represents only a specific instance. Furthermore, using sequence comparison with strictly coupled XylEEc and similar sugar transporters, we identify an additional charged residue that may be essential for effective H+/sugar symport.
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Affiliation(s)
- Andre Bazzone
- Max Planck Institute of Biophysics, Frankfurt/Main, Germany
| | | | | | - M Gregor Madej
- Max Planck Institute of Biophysics, Frankfurt/Main, Germany
| | - Klaus Fendler
- Max Planck Institute of Biophysics, Frankfurt/Main, Germany.
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8
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Abstract
Bacterial sugar symporters in the Major Facilitator Superfamily (MFS) use the H+ (and in a few cases Na+) electrochemical gradients to achieve active transport of sugar into the cell. Because a number of structures of MFS sugar symporters have been solved recently, molecular insight into the transport mechanism is possible from detailed functional analysis. We present here a comparative electrophysiological study of the lactose permease (LacY), the fucose permease (FucP) and the xylose permease (XylE), which reveals common mechanistic principles and differences. In all three symporters energetically downhill electrogenic sugar/H+ symport is observed. Comparison of the pH dependence of symport at symmetrical pH exhibits broad bell-shaped pH profiles extending over 3 to 6 pH units and a decrease at extremely alkaline pH ≥ 9.4 and at acidic to neutral pH = 4.6-7.5. The pH dependence can be described by an acidic to neutral apparent pK (pKapp) and an alkaline pKapp. Experimental evidence suggests that the alkaline pKapp is due to H+ depletion at the protonation site, while the acidic pKapp is due to inhibition of deprotonation. Since previous studies suggest that a single carboxyl group in LacY (Glu325) may be the only side chain directly involved in H+ translocation and a carboxyl side chain with similar properties has been identified in FucP (Asp46) and XylE (Asp27), the present results imply that the pK of this residue is switched during H+/sugar symport in all three symporters.
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Affiliation(s)
- Andre Bazzone
- Department of Biophysical Chemistry, Max-Planck-Institute of Biophysics, Frankfurt/M, Germany
| | - M. Gregor Madej
- Department of Biophysical Chemistry, Max-Planck-Institute of Biophysics, Frankfurt/M, Germany
- Departments of Physiology and Microbiology, Immunology, and Molecular Genetics, Molecular Biology Institute, University of California Los Angeles, Los Angeles, California, United States of America
| | - H. Ronald Kaback
- Departments of Physiology and Microbiology, Immunology, and Molecular Genetics, Molecular Biology Institute, University of California Los Angeles, Los Angeles, California, United States of America
| | - Klaus Fendler
- Department of Biophysical Chemistry, Max-Planck-Institute of Biophysics, Frankfurt/M, Germany
- * E-mail:
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9
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Abstract
The major facilitator superfamily (MFS) is a diverse group of secondary transporters with members found in all kingdoms of life. The paradigm for MFS is the lactose permease (LacY) of Escherichia coli, which has been the test bed for the development of many methods applied for the analysis of transport proteins. X-ray structures of an inward-facing conformation and the most recent structure of an almost occluded conformation confirm many conclusions from previous studies. One fundamentally important problem for understanding the mechanism of secondary active transport is the identification and physical localization of residues involved in substrate and H(+) binding. This information is exceptionally difficult to obtain with the MFS because of the broad sequence diversity among the members. The increasing number of solved MFS structures has led to the recognition of a common feature: inverted structure-repeat, formed by fused triple-helix domains with opposite orientation in the membrane. The presented method here exploits this feature to predict functionally homologous positions of known relevant positions in LacY. The triple-helix motifs are aligned in combinatorial fashion so as to detect substrate and H(+)-binding sites in symporters that transport substrates, ranging from simple ions like phosphate to more complex disaccharides.
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Affiliation(s)
- M Gregor Madej
- Department of Physiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA.
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10
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Nasiri HR, Madej MG, Panisch R, Lafontaine M, Bats JW, Lancaster CRD, Schwalbe H. Design, Synthesis, and Biological Testing of Novel Naphthoquinones as Substrate-Based Inhibitors of the Quinol/Fumarate Reductase from Wolinella succinogenes. J Med Chem 2013; 56:9530-41. [DOI: 10.1021/jm400978u] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hamid Reza Nasiri
- Institute
of Organic Chemistry and Chemical Biology, Center for Biomolecular
Magnetic Resonance, Johann Wolfgang Goethe-University Frankfurt, Max-von-Laue-Straße
7, D-60438 Frankfurt
am Main, Germany
| | - M. Gregor Madej
- Department of
Molecular Membrane Biology, Cluster of Excellence Frankfurt “Macromolecular
Complexes,” Max Planck Institute of Biophysics, Max-von-Laue-Straße 3, D-60438 Frankfurt am Main, Germany
| | - Robin Panisch
- Institute
of Inorganic and Analytical Chemistry, Johann Wolfgang Goethe-University Frankfurt, Max-von-Laue-Straße 7, D-60438 Frankfurt am Main, Germany
| | - Michael Lafontaine
- Department
of Structural Biology, Center of Human and Molecular Biology, Faculty
of Medicine, Saarland University, Building 60, D-66421 Homburg, Germany
| | - Jan W. Bats
- Institute
of Organic Chemistry and Chemical Biology, Center for Biomolecular
Magnetic Resonance, Johann Wolfgang Goethe-University Frankfurt, Max-von-Laue-Straße
7, D-60438 Frankfurt
am Main, Germany
| | - C. Roy D. Lancaster
- Department of
Molecular Membrane Biology, Cluster of Excellence Frankfurt “Macromolecular
Complexes,” Max Planck Institute of Biophysics, Max-von-Laue-Straße 3, D-60438 Frankfurt am Main, Germany
- Department
of Structural Biology, Center of Human and Molecular Biology, Faculty
of Medicine, Saarland University, Building 60, D-66421 Homburg, Germany
| | - Harald Schwalbe
- Institute
of Organic Chemistry and Chemical Biology, Center for Biomolecular
Magnetic Resonance, Johann Wolfgang Goethe-University Frankfurt, Max-von-Laue-Straße
7, D-60438 Frankfurt
am Main, Germany
- German Cancer Consortium
(DKTK), 69120 Heidelberg, Germany
- German Cancer
Research Center (DKFZ), 69120 Heidelberg, Germany
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Zhou Y, Madej MG, Guan L, Nie Y, Kaback HR. An early event in the transport mechanism of LacY protein: interaction between helices V and I. J Biol Chem 2011; 286:30415-30422. [PMID: 21730060 DOI: 10.1074/jbc.m111.268433] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Helix V in LacY, which abuts and crosses helix I in the N-terminal helix bundle of LacY, contains Arg(144) and Trp(151), two residues that play direct roles in sugar recognition and binding, as well as Cys(154), which is important for conformational flexibility. In this study, paired Cys replacement mutants in helices V and I were strategically constructed with tandem factor Xa protease cleavage sites in the loop between the two helices to test cross-linking. None of the mutants form disulfides spontaneously; however, three mutants (Pro(28) → Cys/Cys(154), Pro(28) → Cys/Val(158) → Cys, and Phe(29) → Cys/Val(158) → Cys) exhibit cross-linking after treatment with copper/1,10-phenanthroline (Cu/Ph) or 1,1-methanediyl bismethanethiosulfonate ((MTS)(2)-1), 3-4 Å), and cross-linking is quantitative in the presence of ligand. Remarkably, with one mutant, complete cross-linking with (MTS)(2)-1 has no effect on lactose transport, whereas quantitative disulfide cross-linking catalyzed by Cu/Ph markedly inhibits transport activity. The findings are consistant with a number of previous conclusions suggesting that sugar binding to LacY causes a localized scissors-like movement between helices V and I near the point where the two helices cross in the middle of the membrane. This ligand-induced movement may act to initiate the global conformational change resulting from sugar binding.
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Affiliation(s)
- Yonggang Zhou
- Departments of Physiology, University of California, Los Angeles, California 90095-1662
| | - M Gregor Madej
- Departments of Physiology, University of California, Los Angeles, California 90095-1662
| | - Lan Guan
- Departments of Physiology, University of California, Los Angeles, California 90095-1662
| | - Yiling Nie
- Departments of Physiology, University of California, Los Angeles, California 90095-1662
| | - H Ronald Kaback
- Departments of Physiology, University of California, Los Angeles, California 90095-1662; Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, California 90095-1662; Molecular Biology Institute, University of California, Los Angeles, California 90095-1662.
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12
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Hsieh JM, Besserer GM, Madej MG, Bui HQ, Kwon S, Abramson J. Bridging the gap: a GFP-based strategy for overexpression and purification of membrane proteins with intra and extracellular C-termini. Protein Sci 2010; 19:868-80. [PMID: 20196076 DOI: 10.1002/pro.365] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Low expression and instability during isolation are major obstacles preventing adequate structure-function characterization of membrane proteins (MPs). To increase the likelihood of generating large quantities of protein, C-terminally fused green fluorescent protein (GFP) is commonly used as a reporter for monitoring expression and evaluating purification. This technique has mainly been restricted to MPs with intracellular C-termini (C(in)) due to GFP's inability to fluoresce in the Escherichia coli periplasm. With the aid of Glycophorin A, a single transmembrane spanning protein, we developed a method to convert MPs with extracellular C-termini (C(out)) to C(in) ones providing a conduit for implementing GFP reporting. We tested this method on eleven MPs with predicted C(out) topology resulting in high level expression. For nine of the eleven MPs, a stable, monodisperse protein-detergent complex was identified using an extended fluorescence-detection size exclusion chromatography procedure that monitors protein stability over time, a critical parameter affecting the success of structure-function studies. Five MPs were successfully cleaved from the GFP tag by site-specific proteolysis and purified to homogeneity. To address the challenge of inefficient proteolysis, we explored expression and purification conditions in the absence of the fusion tag. Contrary to previous studies, optimal expression conditions established with the fusion were not directly transferable for overexpression in the absence of the GFP tag. These studies establish a broadly applicable method for GFP screening of MPs with C(out) topology, yielding sufficient protein suitable for structure-function studies and are superior to expression and purification in the absence GFP fusion tagging.
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Affiliation(s)
- Jennifer M Hsieh
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095, USA
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13
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Abstract
Biochemical and biophysical studies based upon crystal structures of both a mutant and wild-type lactose permease from Escherichia coli (LacY) in an inward-facing conformation have led to a model for the symport mechanism in which both sugar and H+ binding sites are alternatively accessible to both sides of the membrane. Previous findings indicate that the face of helix II with Asp68 is important for the conformational changes that occur during turnover. As shown here, replacement of Asp68 at the cytoplasmic end of helix II, particularly with Glu, abolishes active transport but the mutants retain the ability to bind galactopyranoside. In the x-ray structure, Asp68 and Lys131 (helix IV) lie within approximately 4.2 A of each other. Although a double mutant with Cys replacements at both position 68 and position 131 cross-links efficiently, single replacements for Lys131 exhibit very significant transport activity. Site-directed alkylation studies show that sugar binding by the Asp68 mutants causes closure of the cytoplasmic cavity, similar to wild-type LacY; however, strikingly, the probability of opening the periplasmic pathway upon sugar binding is markedly reduced. Taken together with results from previous mutagenesis and cross-linking studies, these findings lead to a model in which replacement of Asp68 blocks a conformational transition involving helices II and IV that is important for opening the periplasmic cavity. Evidence suggesting that movements of helices II and IV are coupled functionally with movements in the pseudo-symmetrically paired helices VIII and X is also presented.
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Affiliation(s)
- Zhenyu Liu
- Department of Physiology, University of California, Los Angeles, Los Angeles, CA 90095-1662, USA
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14
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Nasiri HR, Panisch R, Madej MG, Bats JW, Lancaster CRD, Schwalbe H. The correlation of cathodic peak potentials of vitamin K(3) derivatives and their calculated electron affinities. The role of hydrogen bonding and conformational changes. Biochim Biophys Acta 2009; 1787:601-8. [PMID: 19265668 DOI: 10.1016/j.bbabio.2009.02.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2008] [Revised: 02/16/2009] [Accepted: 02/17/2009] [Indexed: 11/25/2022]
Abstract
2-methyl-1,4-naphtoquinone 1 (vitamin K(3), menadione) derivatives with different substituents at the 3-position were synthesized to tune their electrochemical properties. The thermodynamic midpoint potential (E(1/2)) of the naphthoquinone derivatives yielding a semi radical naphthoquinone anion were measured by cyclic voltammetry in the aprotic solvent dimethoxyethane (DME). Using quantum chemical methods, a clear correlation was found between the thermodynamic midpoint potentials and the calculated electron affinities (E(A)). Comparison of calculated and experimental values allowed delineation of additional factors such as the conformational dependence of quinone substituents and hydrogen bonding which can influence the electron affinities (E(A)) of the quinone. This information can be used as a model to gain insight into enzyme-cofactor interactions, particularly for enzyme quinone binding modes and the electrochemical adjustment of the quinone motif.
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Affiliation(s)
- Hamid Reza Nasiri
- Institute of Organic Chemistry and Chemical Biology, Johann Wolfgang Goethe-University Frankfurt, Max-von-Laue-Str. 7, D-60438 Frankfurt am Main, Germany
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15
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Madej MG, Nasiri HR, Hilgendorff NS, Schwalbe H, Unden G, Lancaster CRD. Experimental evidence for proton motive force-dependent catalysis by the diheme-containing succinate:menaquinone oxidoreductase from the Gram-positive bacterium Bacillus licheniformis. Biochemistry 2007; 45:15049-55. [PMID: 17154542 DOI: 10.1021/bi0618161] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In Gram-positive bacteria and other prokaryotes containing succinate:menaquinone reductases, it has previously been shown that the succinate oxidase and succinate:menaquinone reductase activities are lost when the transmembrane electrochemical proton potential, Deltap, is abolished by the rupture of the bacteria or by the addition of a protonophore. It has been proposed that the endergonic reduction of menaquinone by succinate is driven by the electrochemical proton potential. Opposite sides of the cytoplasmic membrane were envisaged to be separately involved in the binding of protons upon the reduction of menaquinone and their release upon succinate oxidation, with the two reactions linked by the transfer of two electrons through the enzyme. However, it has previously been argued that the observed Deltap dependence is not associated specifically with the succinate:menaquinone reductase. Definitive insight into the mechanism of catalysis of this reaction requires a corresponding functional characterization of an isolated, membrane-bound succinate:menaquinone reductase from a Gram-positive bacterium. Here, we describe the purification, reconstitution into proteoliposomes, and functional characterization of the diheme-containing succinate:menaquinone reductase from the Gram-positive bacterium Bacillus licheniformis and, with the help of the design, synthesis, and characterization of quinones with finely tuned oxidation/reduction potentials, provide unequivocal evidence for Deltap-dependent catalysis of succinate oxidation by quinone as well as for Deltap generation upon catalysis of fumarate reduction by quinol.
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Affiliation(s)
- M Gregor Madej
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, D-60438 Frankfurt am Main, Germany
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16
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Nasiri HR, Madej MG, Lancaster CRD, Schwalbe H, Bolte M. 2-Hydroxy-3-(3-oxobutyl)naphthalene-1,4-dione. Acta Crystallogr C 2006; 62:o671-3. [PMID: 17148908 DOI: 10.1107/s0108270106042211] [Citation(s) in RCA: 2] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2006] [Accepted: 10/11/2006] [Indexed: 11/10/2022] Open
Abstract
The title compound, C14H12O4, forms crystals which appear monoclinic but are actually twinned triclinic. The asymmetric unit consists of two similar molecules, which differ only in the conformation of the 3-oxobutyl side chain. The molecular conformation is characterized by an intramolecular O-H...O hydrogen bond between the hydroxy group and the adjacent carbonyl O atom. The crystal structure is stabilized by O-H...O hydrogen bonds connecting the molecules into zigzag chains running along the b axis.
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Affiliation(s)
- Hamid Reza Nasiri
- Institute of Organic Chemistry and Chemical Biology, Center for Biomolecular Magnetic Resonance, J W Goethe-Universität Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt/Main, Germany
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17
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Madej MG, Nasiri HR, Hilgendorff NS, Schwalbe H, Lancaster CRD. Evidence for transmembrane proton transfer in a dihaem-containing membrane protein complex. EMBO J 2006; 25:4963-70. [PMID: 17024183 PMCID: PMC1618101 DOI: 10.1038/sj.emboj.7601361] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [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: 04/07/2006] [Accepted: 08/28/2006] [Indexed: 11/09/2022] Open
Abstract
Membrane protein complexes can support both the generation and utilisation of a transmembrane electrochemical proton potential ('proton-motive force'), either by transmembrane electron transfer coupled to protolytic reactions on opposite sides of the membrane or by transmembrane proton transfer. Here we provide the first evidence that both of these mechanisms are combined in the case of a specific respiratory membrane protein complex, the dihaem-containing quinol:fumarate reductase (QFR) of Wolinella succinogenes, so as to facilitate transmembrane electron transfer by transmembrane proton transfer. We also demonstrate the non-functionality of this novel transmembrane proton transfer pathway ('E-pathway') in a variant QFR where a key glutamate residue has been replaced. The 'E-pathway', discussed on the basis of the 1.78-Angstrom-resolution crystal structure of QFR, can be concluded to be essential also for the viability of pathogenic epsilon-proteobacteria such as Helicobacter pylori and is possibly relevant to proton transfer in other dihaem-containing membrane proteins, performing very different physiological functions.
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Affiliation(s)
- M Gregor Madej
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Hamid R Nasiri
- Institut für Organische Chemie und Chemische Biologie, Center for Biomolecular Magnetic Resonance, Johann Wolfgang Goethe-Universität, Frankfurt am Main, Germany
| | - Nicole S Hilgendorff
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Harald Schwalbe
- Institut für Organische Chemie und Chemische Biologie, Center for Biomolecular Magnetic Resonance, Johann Wolfgang Goethe-Universität, Frankfurt am Main, Germany
| | - C Roy D Lancaster
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Max-von-Laue-Str. 3, PO Box 55 03 53, 60402 Frankfurt am Main, Germany. Tel.: +49 69 6303 1013; Fax: +49 69 6303 1002; E-mail:
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18
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Lancaster CRD, Haas AH, Madej MG, Mileni M. Recent progress on obtaining theoretical and experimental support for the “E-pathway hypothesis” of coupled transmembrane electron and proton transfer in dihaem-containing quinol:fumarate reductase. Biochimica et Biophysica Acta (BBA) - Bioenergetics 2006; 1757:988-95. [PMID: 16790236 DOI: 10.1016/j.bbabio.2006.05.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2006] [Revised: 04/27/2006] [Accepted: 05/02/2006] [Indexed: 11/29/2022]
Abstract
Reconciliation of apparently contradictory experimental results obtained on the quinol: fumarate reductase (QFR), a dihaem-containing respiratory membrane protein complex from Wolinella succinogenes, was previously obtained by the proposal of the so-called E-pathway hypothesis. According to this hypothesis, transmembrane electron transfer via the haem groups is strictly coupled to co-transfer of protons via a transiently established, novel pathway, proposed to contain the side chain of residue Glu-C180 and the distal haem ring-C propionate as the most prominent components. This hypothesis has recently been supported by both theoretical and experimental results. Multiconformation continuum electrostatics calculations predict Glu-C180 to undergo a combination of proton uptake and conformational change upon haem reduction. Strong experimental support for the proposed role of Glu-C180 in the context of the "E-pathway hypothesis" is provided by the effects of replacing Glu-C180 with Gln or Ile by site-directed mutagenesis, the consequences of these mutations for the viability of the resulting mutants, together with the structural and functional characterisation of the corresponding variant enzymes, and the comparison of redox-induced Fourier-transform infrared (FTIR) difference spectra for the wild type and Glu-C180-->Gln variant. A possible haem propionate involvement has recently been supported by combining (13)C-haem propionate labelling with redox-induced FTIR difference spectroscopy.
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Affiliation(s)
- C Roy D Lancaster
- Max Planck Institute of Biophysics, Department of Molecular Membrane Biology, Max-Von-Laue-Str 3, Frankfurt am Main, Germany.
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Lancaster CRD, Sauer US, Gross R, Haas AH, Graf J, Schwalbe H, Mäntele W, Simon J, Madej MG. Experimental support for the "E pathway hypothesis" of coupled transmembrane e- and H+ transfer in dihemic quinol:fumarate reductase. Proc Natl Acad Sci U S A 2005; 102:18860-5. [PMID: 16380425 PMCID: PMC1323215 DOI: 10.1073/pnas.0509711102] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2005] [Indexed: 11/18/2022] Open
Abstract
Reconciliation of apparently contradictory experimental results obtained on the quinol:fumarate reductase, a diheme-containing respiratory membrane protein complex from Wolinella succinogenes, was previously obtained by the proposal of the so-called "E pathway hypothesis." According to this hypothesis, transmembrane electron transfer via the heme groups is strictly coupled to cotransfer of protons via a transiently established pathway thought to contain the side chain of residue Glu-C180 as the most prominent component. Here we demonstrate that, after replacement of Glu-C180 with Gln or Ile by site-directed mutagenesis, the resulting mutants are unable to grow on fumarate, and the membrane-bound variant enzymes lack quinol oxidation activity. Upon solubilization, however, the purified enzymes display approximately 1/10 of the specific quinol oxidation activity of the wild-type enzyme and unchanged quinol Michaelis constants, K(m). The refined x-ray crystal structures at 2.19 A and 2.76 A resolution, respectively, rule out major structural changes to account for these experimental observations. Changes in the oxidation-reduction heme midpoint potential allow the conclusion that deprotonation of Glu-C180 in the wild-type enzyme facilitates the reoxidation of the reduced high-potential heme. Comparison of solvent isotope effects indicates that a rate-limiting proton transfer step in the wild-type enzyme is lost in the Glu-C180 --> Gln variant. The results provide experimental evidence for the validity of the E pathway hypothesis and for a crucial functional role of Glu-C180.
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Affiliation(s)
- C Roy D Lancaster
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, D-60438 Frankfurt am Main, Germany.
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