1
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Zhao CR, You ZL, Bai L. Fungal Plasma Membrane H +-ATPase: Structure, Mechanism, and Drug Discovery. J Fungi (Basel) 2024; 10:273. [PMID: 38667944 PMCID: PMC11051447 DOI: 10.3390/jof10040273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Revised: 04/01/2024] [Accepted: 04/02/2024] [Indexed: 04/28/2024] Open
Abstract
The fungal plasma membrane H+-ATPase (Pma1) pumps protons out of the cell to maintain the transmembrane electrochemical gradient and membrane potential. As an essential P-type ATPase uniquely found in fungi and plants, Pma1 is an attractive antifungal drug target. Two recent Cryo-EM studies on Pma1 have revealed its hexameric architecture, autoinhibitory and activation mechanisms, and proton transport mechanism. These structures provide new perspectives for the development of antifungal drugs targeting Pma1. In this article, we review the history of Pma1 structure determination, the latest structural insights into Pma1, and drug discoveries targeting Pma1.
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Affiliation(s)
- Chao-Ran Zhao
- Department of Otolaryngology Head and Neck Surgery, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China
- Beijing Key Laboratory of Nasal Diseases, Beijing Institute of Otolaryngology, Beijing 100005, China
| | - Zi-Long You
- Department of Biophysics, School of Basic Medical Sciences, Peking University, Beijing 100083, China
| | - Lin Bai
- Department of Biophysics, School of Basic Medical Sciences, Peking University, Beijing 100083, China
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2
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Young MR, Heit S, Bublitz M. Structure, function and biogenesis of the fungal proton pump Pma1. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2024; 1871:119600. [PMID: 37741574 DOI: 10.1016/j.bbamcr.2023.119600] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 08/19/2023] [Accepted: 09/18/2023] [Indexed: 09/25/2023]
Abstract
The fungal plasma membrane proton pump Pma1 is an integral plasma membrane protein of the P-type ATPase family. It is an essential enzyme responsible for maintaining a constant cytosolic pH and for energising the plasma membrane to secondary transport processes. Due to its importance for fungal survival and absence from animals, Pma1 is also a highly sought-after drug target. Until recently, its characterisation has been limited to functional, mutational and localisation studies, due to a lack of high-resolution structural information. The determination of three cryo-EM structures of Pma1 in its unique hexameric state offers a new level of understanding the molecular mechanisms underlying the protein's stability, regulated activity and druggability. In light of this context, this article aims to review what we currently know about the structure, function and biogenesis of fungal Pma1.
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Affiliation(s)
- Margaret R Young
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
| | - Sabine Heit
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
| | - Maike Bublitz
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom.
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3
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Palmgren M. P-type ATPases: Many more enigmas left to solve. J Biol Chem 2023; 299:105352. [PMID: 37838176 PMCID: PMC10654040 DOI: 10.1016/j.jbc.2023.105352] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 10/02/2023] [Accepted: 10/05/2023] [Indexed: 10/16/2023] Open
Abstract
P-type ATPases constitute a large ancient super-family of primary active pumps that have diverse substrate specificities ranging from H+ to phospholipids. The significance of these enzymes in biology cannot be overstated. They are structurally related, and their catalytic cycles alternate between high- and low-affinity conformations that are induced by phosphorylation and dephosphorylation of a conserved aspartate residue. In the year 1988, all P-type sequences available by then were analyzed and five major families, P1 to P5, were identified. Since then, a large body of knowledge has accumulated concerning the structure, function, and physiological roles of members of these families, but only one additional family, P6 ATPases, has been identified. However, much is still left to be learned. For each family a few remaining enigmas are presented, with the intention that they will stimulate interest in continued research in the field. The review is by no way comprehensive and merely presents personal views with a focus on evolution.
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Affiliation(s)
- Michael Palmgren
- Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg C, Denmark.
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4
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Paweletz LC, Holtbrügge SL, Löb M, De Vecchis D, Schäfer LV, Günther Pomorski T, Justesen BH. Anionic Phospholipids Stimulate the Proton Pumping Activity of the Plant Plasma Membrane P-Type H +-ATPase. Int J Mol Sci 2023; 24:13106. [PMID: 37685912 PMCID: PMC10488199 DOI: 10.3390/ijms241713106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Revised: 08/16/2023] [Accepted: 08/18/2023] [Indexed: 09/10/2023] Open
Abstract
The activity of membrane proteins depends strongly on the surrounding lipid environment. Here, we characterize the lipid stimulation of the plant plasma membrane H+-ATPase Arabidopsis thaliana H+-ATPase isoform 2 (AHA2) upon purification and reconstitution into liposomes of defined lipid compositions. We show that the proton pumping activity of AHA2 is stimulated by anionic phospholipids, especially by phosphatidylserine. This activation was independent of the cytoplasmic C-terminal regulatory domain of the pump. Molecular dynamics simulations revealed several preferential contact sites for anionic phospholipids in the transmembrane domain of AHA2. These contact sites are partially conserved in functionally different P-type ATPases from different organisms, suggesting a general regulation mechanism by the membrane lipid environment. Our findings highlight the fact that anionic lipids play an important role in the control of H+-ATPase activity.
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Affiliation(s)
- Laura C. Paweletz
- Department of Molecular Biochemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, 44780 Bochum, Germany; (L.C.P.); (M.L.); (T.G.P.)
| | - Simon L. Holtbrügge
- Center for Theoretical Chemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, 44780 Bochum, Germany; (S.L.H.); (D.D.V.)
| | - Malina Löb
- Department of Molecular Biochemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, 44780 Bochum, Germany; (L.C.P.); (M.L.); (T.G.P.)
| | - Dario De Vecchis
- Center for Theoretical Chemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, 44780 Bochum, Germany; (S.L.H.); (D.D.V.)
| | - Lars V. Schäfer
- Center for Theoretical Chemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, 44780 Bochum, Germany; (S.L.H.); (D.D.V.)
| | - Thomas Günther Pomorski
- Department of Molecular Biochemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, 44780 Bochum, Germany; (L.C.P.); (M.L.); (T.G.P.)
- Department of Plant and Environmental Sciences, University of Copenhagen, 1871 Frederiksberg C, Denmark
| | - Bo Højen Justesen
- Department of Molecular Biochemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, 44780 Bochum, Germany; (L.C.P.); (M.L.); (T.G.P.)
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5
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Lapshin NK, Piotrovskii MS, Trofimova MS. Sterol Extraction from Isolated Plant Plasma Membrane Vesicles Affects H +-ATPase Activity and H +-Transport. Biomolecules 2021; 11:1891. [PMID: 34944535 PMCID: PMC8699270 DOI: 10.3390/biom11121891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Revised: 12/14/2021] [Accepted: 12/15/2021] [Indexed: 11/16/2022] Open
Abstract
Plasma membrane H+-ATPase is known to be detected in detergent-resistant sterol-enriched fractions, also called "raft" domains. Studies on H+-ATPase reconstituted in artificial or native membrane vesicles have shown both sterol-mediated stimulations and inhibitions of its activity. Here, using sealed isolated plasma membrane vesicles, we investigated the effects of sterol depletion in the presence of methyl-β-cyclodextrin (MβCD) on H+-ATPase activity. The rate of ATP-dependent ∆µH+ generation and the kinetic parameters of ATP hydrolysis were evaluated. We show that the relative sterols content in membrane vesicles decreased gradually after treatment with MβCD and reached approximately 40% of their initial level in 30 mM probe solution. However, changes in the hydrolytic and H+-transport activities of the enzyme were nonlinear. The extraction of up to 20% of the initial sterols was accompanied by strong stimulation of ATP-dependent H+-transport in comparison with the hydrolytic activity of enzymes. Further sterol depletion led to a significant inhibition of active proton transport with an increase in passive H+-leakage. The solubilization of control and sterol-depleted vesicles in the presence of dodecyl maltoside negated the differences in the kinetics parameters of ATP hydrolysis, and all samples demonstrated maximal hydrolytic activities. The mechanisms behind the sensitivity of ATP-dependent H+-transport to sterols in the lipid environment of plasma membrane H+-ATPase are discussed.
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Affiliation(s)
| | | | - Marina S. Trofimova
- K.A. Timiryazev Institute of Plant Physiology of the Russian Academy of Sciences (IPP RAS), 35 Botanicheskaya St., 127276 Moscow, Russia; (N.K.L.); (M.S.P.)
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6
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Zhou JY, Hao DL, Yang GZ. Regulation of Cytosolic pH: The Contributions of Plant Plasma Membrane H +-ATPases and Multiple Transporters. Int J Mol Sci 2021; 22:12998. [PMID: 34884802 PMCID: PMC8657649 DOI: 10.3390/ijms222312998] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 11/24/2021] [Accepted: 11/25/2021] [Indexed: 11/17/2022] Open
Abstract
Cytosolic pH homeostasis is a precondition for the normal growth and stress responses in plants, and H+ flux across the plasma membrane is essential for cytoplasmic pH control. Hence, this review focuses on seven types of proteins that possess direct H+ transport activity, namely, H+-ATPase, NHX, CHX, AMT, NRT, PHT, and KT/HAK/KUP, to summarize their plasma-membrane-located family members, the effect of corresponding gene knockout and/or overexpression on cytosolic pH, the H+ transport pathway, and their functional regulation by the extracellular/cytosolic pH. In general, H+-ATPases mediate H+ extrusion, whereas most members of other six proteins mediate H+ influx, thus contributing to cytosolic pH homeostasis by directly modulating H+ flux across the plasma membrane. The fact that some AMTs/NRTs mediate H+-coupled substrate influx, whereas other intra-family members facilitate H+-uncoupled substrate transport, demonstrates that not all plasma membrane transporters possess H+-coupled substrate transport mechanisms, and using the transport mechanism of a protein to represent the case of the entire family is not suitable. The transport activity of these proteins is regulated by extracellular and/or cytosolic pH, with different structural bases for H+ transfer among these seven types of proteins. Notably, intra-family members possess distinct pH regulatory characterization and underlying residues for H+ transfer. This review is anticipated to facilitate the understanding of the molecular basis for cytosolic pH homeostasis. Despite this progress, the strategy of their cooperation for cytosolic pH homeostasis needs further investigation.
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Affiliation(s)
- Jin-Yan Zhou
- Jiangsu Vocational College of Agriculture and Forest, Jurong 212400, China;
| | - Dong-Li Hao
- The National Forestry and Grassland Administration Engineering Research Center for Germplasm Innovation and Utilization of Warm-Season Turfgrasses, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing 210014, China
| | - Guang-Zhe Yang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Science and Technology, Guangxi University, Nanning 530004, China;
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7
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Heit S, Geurts MMG, Murphy BJ, Corey RA, Mills DJ, Kühlbrandt W, Bublitz M. Structure of the hexameric fungal plasma membrane proton pump in its autoinhibited state. SCIENCE ADVANCES 2021; 7:eabj5255. [PMID: 34757782 DOI: 10.1101/2021.04.30.442159] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The fungal plasma membrane H+-ATPase Pma1 is a vital enzyme, generating a proton-motive force that drives the import of essential nutrients. Autoinhibited Pma1 hexamers in the plasma membrane of starving fungi are activated by glucose signaling and subsequent phosphorylation of the autoinhibitory domain. As related P-type adenosine triphosphatases (ATPases) are not known to oligomerize, the physiological relevance of Pma1 hexamers remained unknown. We have determined the structure of hexameric Pma1 from Neurospora crassa by electron cryo-microscopy at 3.3-Å resolution, elucidating the molecular basis for hexamer formation and autoinhibition and providing a basis for structure-based drug development. Coarse-grained molecular dynamics simulations in a lipid bilayer suggest lipid-mediated contacts between monomers and a substantial protein-induced membrane deformation that could act as a proton-attracting funnel.
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Affiliation(s)
- Sabine Heit
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Maxwell M G Geurts
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Bonnie J Murphy
- Max Planck Institute of Biophysics, Max-von-Laue-Str.3, 60438 Frankfurt am Main, Germany
| | - Robin A Corey
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Deryck J Mills
- Max Planck Institute of Biophysics, Max-von-Laue-Str.3, 60438 Frankfurt am Main, Germany
| | - Werner Kühlbrandt
- Max Planck Institute of Biophysics, Max-von-Laue-Str.3, 60438 Frankfurt am Main, Germany
| | - Maike Bublitz
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
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8
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Heit S, Geurts MMG, Murphy BJ, Corey RA, Mills DJ, Kühlbrandt W, Bublitz M. Structure of the hexameric fungal plasma membrane proton pump in its autoinhibited state. SCIENCE ADVANCES 2021; 7:eabj5255. [PMID: 34757782 PMCID: PMC8580308 DOI: 10.1126/sciadv.abj5255] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 09/22/2021] [Indexed: 05/11/2023]
Abstract
The fungal plasma membrane H+-ATPase Pma1 is a vital enzyme, generating a proton-motive force that drives the import of essential nutrients. Autoinhibited Pma1 hexamers in the plasma membrane of starving fungi are activated by glucose signaling and subsequent phosphorylation of the autoinhibitory domain. As related P-type adenosine triphosphatases (ATPases) are not known to oligomerize, the physiological relevance of Pma1 hexamers remained unknown. We have determined the structure of hexameric Pma1 from Neurospora crassa by electron cryo-microscopy at 3.3-Å resolution, elucidating the molecular basis for hexamer formation and autoinhibition and providing a basis for structure-based drug development. Coarse-grained molecular dynamics simulations in a lipid bilayer suggest lipid-mediated contacts between monomers and a substantial protein-induced membrane deformation that could act as a proton-attracting funnel.
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Affiliation(s)
- Sabine Heit
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Maxwell M. G. Geurts
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Bonnie J. Murphy
- Max Planck Institute of Biophysics, Max-von-Laue-Str.3, 60438 Frankfurt am Main, Germany
| | - Robin A. Corey
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - Deryck J. Mills
- Max Planck Institute of Biophysics, Max-von-Laue-Str.3, 60438 Frankfurt am Main, Germany
| | - Werner Kühlbrandt
- Max Planck Institute of Biophysics, Max-von-Laue-Str.3, 60438 Frankfurt am Main, Germany
| | - Maike Bublitz
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
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9
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Zhao P, Zhao C, Chen D, Yun C, Li H, Bai L. Structure and activation mechanism of the hexameric plasma membrane H +-ATPase. Nat Commun 2021; 12:6439. [PMID: 34750373 PMCID: PMC8575881 DOI: 10.1038/s41467-021-26782-y] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2021] [Accepted: 10/22/2021] [Indexed: 11/29/2022] Open
Abstract
The S. cerevisiae plasma membrane H+-ATPase, Pma1, is a P3A-type ATPase and the primary protein component of the membrane compartment of Pma1 (MCP). Like other plasma membrane H+-ATPases, Pma1 assembles and functions as a hexamer, a property unique to this subfamily among the larger family of P-type ATPases. It has been unclear how Pma1 organizes the yeast membrane into MCP microdomains, or why it is that Pma1 needs to assemble into a hexamer to establish the membrane electrochemical proton gradient. Here we report a high-resolution cryo-EM study of native Pma1 hexamers embedded in endogenous lipids. Remarkably, we found that the Pma1 hexamer encircles a liquid-crystalline membrane domain composed of 57 ordered lipid molecules. The Pma1-encircled lipid patch structure likely serves as the building block of the MCP. At pH 7.4, the carboxyl-terminal regulatory α-helix binds to the phosphorylation domains of two neighboring Pma1 subunits, locking the hexamer in the autoinhibited state. The regulatory helix becomes disordered at lower pH, leading to activation of the Pma1 hexamer. The activation process is accompanied by a 6.7 Å downward shift and a 40° rotation of transmembrane helices 1 and 2 that line the proton translocation path. The conformational changes have enabled us to propose a detailed mechanism for ATP-hydrolysis-driven proton pumping across the plasma membrane. Our structures will facilitate the development of antifungal drugs that target this essential protein.
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Affiliation(s)
- Peng Zhao
- Department of Biochemistry and Biophysics, School of Basic Medical Sciences, Peking University, Beijing, China
| | - Chaoran Zhao
- Department of Biochemistry and Biophysics, School of Basic Medical Sciences, Peking University, Beijing, China
| | - Dandan Chen
- Department of Biochemistry and Biophysics, School of Basic Medical Sciences, Peking University, Beijing, China
| | - Caihong Yun
- Department of Biochemistry and Biophysics, School of Basic Medical Sciences, Peking University, Beijing, China
| | - Huilin Li
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI, USA.
| | - Lin Bai
- Department of Biochemistry and Biophysics, School of Basic Medical Sciences, Peking University, Beijing, China.
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10
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Bondar AN. Proton-Binding Motifs of Membrane-Bound Proteins: From Bacteriorhodopsin to Spike Protein S. Front Chem 2021; 9:685761. [PMID: 34136464 PMCID: PMC8203321 DOI: 10.3389/fchem.2021.685761] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 05/18/2021] [Indexed: 11/13/2022] Open
Abstract
Membrane-bound proteins that change protonation during function use specific protein groups to bind and transfer protons. Knowledge of the identity of the proton-binding groups is of paramount importance to decipher the reaction mechanism of the protein, and protonation states of prominent are studied extensively using experimental and computational approaches. Analyses of model transporters and receptors from different organisms, and with widely different biological functions, indicate common structure-sequence motifs at internal proton-binding sites. Proton-binding dynamic hydrogen-bond networks that are exposed to the bulk might provide alternative proton-binding sites and proton-binding pathways. In this perspective article I discuss protonation coupling and proton binding at internal and external carboxylate sites of proteins that use proton transfer for function. An inter-helical carboxylate-hydroxyl hydrogen-bond motif is present at functionally important sites of membrane proteins from archaea to the brain. External carboxylate-containing H-bond clusters are observed at putative proton-binding sites of protonation-coupled model proteins, raising the question of similar functionality in spike protein S.
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Affiliation(s)
- Ana-Nicoleta Bondar
- Freie Universität Berlin, Department of Physics, Theoretical Molecular Biophysics Group, Berlin, Germany
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11
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Kabra R, Singh S. Transporter proteins and its implication in human diseases. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2020; 124:1-21. [PMID: 33632463 DOI: 10.1016/bs.apcsb.2020.08.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Drug transporters, classified in various ways like efflux transporters and influx transporters; secretory transporters and absorptive transporters; ATP-driven transporters and Solute Linked Carrier (SLC) transporters are of great importance while studying pharmacokinetics. They have impeccable roles in the drug discovery process of infectious diseases. Many of these find a pivotal role in synthetic antimicrobial peptides. The chapter briefly elucidates the varied types and their significance.
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Affiliation(s)
- Ritika Kabra
- National Centre for Cell Science, SP Pune University Campus, Pune, India
| | - Shailza Singh
- National Centre for Cell Science, SP Pune University Campus, Pune, India.
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12
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Hoffmann RD, Portes MT, Olsen LI, Damineli DSC, Hayashi M, Nunes CO, Pedersen JT, Lima PT, Campos C, Feijó JA, Palmgren M. Plasma membrane H +-ATPases sustain pollen tube growth and fertilization. Nat Commun 2020; 11:2395. [PMID: 32409656 PMCID: PMC7224221 DOI: 10.1038/s41467-020-16253-1] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Accepted: 04/23/2020] [Indexed: 01/18/2023] Open
Abstract
Pollen tubes are highly polarized tip-growing cells that depend on cytosolic pH gradients for signaling and growth. Autoinhibited plasma membrane proton (H+) ATPases (AHAs) have been proposed to energize pollen tube growth and underlie cell polarity, however, mechanistic evidence for this is lacking. Here we report that the combined loss of AHA6, AHA8, and AHA9 in Arabidopsis thaliana delays pollen germination and causes pollen tube growth defects, leading to drastically reduced fertility. Pollen tubes of aha mutants had reduced extracellular proton (H+) and anion fluxes, reduced cytosolic pH, reduced tip-to-shank proton gradients, and defects in actin organization. Furthermore, mutant pollen tubes had less negative membrane potentials, substantiating a mechanistic role for AHAs in pollen tube growth through plasma membrane hyperpolarization. Our findings define AHAs as energy transducers that sustain the ionic circuit defining the spatial and temporal profiles of cytosolic pH, thereby controlling downstream pH-dependent mechanisms essential for pollen tube elongation, and thus plant fertility.
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Affiliation(s)
- Robert D Hoffmann
- Department for Plant and Environmental Sciences, University of Copenhagen, 1871, Frederiksberg C, Denmark
| | - Maria Teresa Portes
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD, 20742, USA
| | - Lene Irene Olsen
- Department for Plant and Environmental Sciences, University of Copenhagen, 1871, Frederiksberg C, Denmark
| | - Daniel Santa Cruz Damineli
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD, 20742, USA
- Department of Pediatrics, Faculdade de Medicina da Universidade de São Paulo, São Paulo, SP, 01246-903, Brazil
| | - Maki Hayashi
- Department for Plant and Environmental Sciences, University of Copenhagen, 1871, Frederiksberg C, Denmark
| | - Custódio O Nunes
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD, 20742, USA
| | - Jesper T Pedersen
- Department for Plant and Environmental Sciences, University of Copenhagen, 1871, Frederiksberg C, Denmark
| | - Pedro T Lima
- Instituto Gulbenkian de Ciência, Oeiras, 2780-156, Portugal
| | - Cláudia Campos
- Instituto Gulbenkian de Ciência, Oeiras, 2780-156, Portugal
| | - José A Feijó
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD, 20742, USA.
- Instituto Gulbenkian de Ciência, Oeiras, 2780-156, Portugal.
| | - Michael Palmgren
- Department for Plant and Environmental Sciences, University of Copenhagen, 1871, Frederiksberg C, Denmark.
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13
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Palmgren M, Morsomme P. The plasma membrane H + -ATPase, a simple polypeptide with a long history. Yeast 2019; 36:201-210. [PMID: 30447028 PMCID: PMC6590192 DOI: 10.1002/yea.3365] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 11/08/2018] [Accepted: 11/11/2018] [Indexed: 11/11/2022] Open
Abstract
The plasma membrane H+ -ATPase of fungi and plants is a single polypeptide of fewer than 1,000 residues that extrudes protons from the cell against a large electric and concentration gradient. The minimalist structure of this nanomachine is in stark contrast to that of the large multi-subunit FO F1 ATPase of mitochondria, which is also a proton pump, but under physiological conditions runs in the reverse direction to act as an ATP synthase. The plasma membrane H+ -ATPase is a P-type ATPase, defined by having an obligatory phosphorylated reaction cycle intermediate, like cation pumps of animal membranes, and thus, this pump has a completely different mechanism to that of FO F1 ATPases, which operates by rotary catalysis. The work that led to these insights in plasma membrane H+ -ATPases of fungi and plants has a long history, which is briefly summarized in this review.
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Affiliation(s)
- Michael Palmgren
- Department of Plant and Environmental SciencesUniversity of CopenhagenFrederiksberg CDenmark
| | - Pierre Morsomme
- Louvain Institute of Biomolecular Science and Technology (LIBST)UCLouvainLouvain‐la‐NeuveBelgium
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14
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Zhang S, Habets M, Breuninger H, Dolan L, Offringa R, van Duijn B. Evolutionary and Functional Analysis of a Chara Plasma Membrane H +-ATPase. FRONTIERS IN PLANT SCIENCE 2019; 10:1707. [PMID: 32038681 PMCID: PMC6985207 DOI: 10.3389/fpls.2019.01707] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Accepted: 12/04/2019] [Indexed: 05/12/2023]
Abstract
H+-ATPases are the main transporters in plant and fungal plasma membranes (PMs), comparable to the Na+/K+ ATPases in animal cells. At the molecular level, most studies on the PM H+-ATPases have been focused on land plants and fungi (yeast). The research of PM H+-ATPases in green algae falls far behind due to the lack of genetic information. Here we studied a potential PM H+-ATPase (CHA1) from Chara australis, a species of green algae belonging to the division Charophyta, members of which are considered to be one of the closest ancestors of land plants. The gene encodes a 107 kDa protein with all 6 P-type ATPase-specific motifs and a long, diverse C-terminal domain. A new amino acid sequence motif R*****Q in transmembrane segment 5 was identified among the known PM H+-ATPases from Charophyta and Chlorophyta algae, which is different from the typical PM H+-ATPases in yeast or land plants. Complementation analysis in yeast showed that CHA1 could successfully reach the PM, and that proton pump activity was obtained when the last 77 up to 87 amino acids of the C-terminal domain were deleted. PM localization was confirmed in Arabidopsis protoplasts; however, deletion of more than 55 amino acids at the N-terminus or more than 98 amino acids at the C-terminus resulted in failure of CHA1 to reach the PM in yeast. These results suggest that an auto-inhibition domain is located in the C-terminal domain, and that CHA1 is likely to have a different regulation mechanism compared to the yeast and land plant PM H+-ATPases.
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Affiliation(s)
- Suyun Zhang
- Plant Biodynamics Laboratory, Institute of Biology Leiden, Leiden University, Leiden, Netherlands
- Plant Developmental Genetics, Institute of Biology Leiden, Leiden University, Leiden, Netherlands
- School of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, China
| | - Myckel Habets
- Plant Developmental Genetics, Institute of Biology Leiden, Leiden University, Leiden, Netherlands
| | - Holger Breuninger
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom
| | - Liam Dolan
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom
| | - Remko Offringa
- Plant Developmental Genetics, Institute of Biology Leiden, Leiden University, Leiden, Netherlands
| | - Bert van Duijn
- Plant Biodynamics Laboratory, Institute of Biology Leiden, Leiden University, Leiden, Netherlands
- Research Department, Fytagoras BV, Leiden, Netherlands
- *Correspondence: Bert van Duijn,
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15
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Focht D, Croll TI, Pedersen BP, Nissen P. Improved Model of Proton Pump Crystal Structure Obtained by Interactive Molecular Dynamics Flexible Fitting Expands the Mechanistic Model for Proton Translocation in P-Type ATPases. Front Physiol 2017; 8:202. [PMID: 28443028 PMCID: PMC5387105 DOI: 10.3389/fphys.2017.00202] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Accepted: 03/20/2017] [Indexed: 11/22/2022] Open
Abstract
The plasma membrane H+-ATPase is a proton pump of the P-type ATPase family and essential in plants and fungi. It extrudes protons to regulate pH and maintains a strong proton-motive force that energizes e.g., secondary uptake of nutrients. The only crystal structure of a H+-ATPase (AHA2 from Arabidopsis thaliana) was reported in 2007. Here, we present an improved atomic model of AHA2, obtained by a combination of model rebuilding through interactive molecular dynamics flexible fitting (iMDFF) and structural refinement based on the original data, but using up-to-date refinement methods. More detailed map features prompted local corrections of the transmembrane domain, in particular rearrangement of transmembrane helices 7 and 8, and the cytoplasmic N- and P-domains, and the new model shows improved overall quality and reliability scores. The AHA2 structure shows similarity to the Ca2+-ATPase E1 state, and provides a valuable starting point model for structural and functional analysis of proton transport mechanism of P-type H+-ATPases. Specifically, Asp684 protonation associated with phosphorylation and occlusion of the E1P state may result from hydrogen bond interaction with Asn106. A subsequent deprotonation associated with extracellular release in the E2P state may result from an internal salt bridge formation to an Arg655 residue, which in the present E1 state is stabilized in a solvated pocket. A release mechanism based on an in-built counter-cation was also later proposed for Zn2+-ATPase, for which structures have been determined in Zn2+ released E2P-like states with the salt bridge interaction formed.
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Affiliation(s)
- Dorota Focht
- Department of Molecular Biology and Genetics, Aarhus UniversityAarhus, Denmark.,DANDRITE, Nordic-EMBL Partnership for Molecular Medicine, Aarhus UniversityAarhus, Denmark.,PUMPkin, Danish National Research Foundation, Aarhus UniversityAarhus, Denmark
| | - Tristan I Croll
- Institute of Health Biomedical Innovation, Queensland University of TechnologyBrisbane, QLD, Australia
| | - Bjorn P Pedersen
- Department of Molecular Biology and Genetics, Aarhus UniversityAarhus, Denmark.,PUMPkin, Danish National Research Foundation, Aarhus UniversityAarhus, Denmark.,Aarhus Institute of Advanced Studies, Aarhus UniversityAarhus, Denmark
| | - Poul Nissen
- Department of Molecular Biology and Genetics, Aarhus UniversityAarhus, Denmark.,DANDRITE, Nordic-EMBL Partnership for Molecular Medicine, Aarhus UniversityAarhus, Denmark.,PUMPkin, Danish National Research Foundation, Aarhus UniversityAarhus, Denmark
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16
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Petrov VV. Functioning of Yeast Pma1 H+-ATPase under Changing Charge: Role of Asp739 and Arg811 Residues. BIOCHEMISTRY. BIOKHIMIIA 2017; 82:46-59. [PMID: 28320286 DOI: 10.1134/s0006297917010059] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The plasma membrane Pma1 H+-ATPase of the yeast Saccharomyces cerevisiae contains conserved residue Asp739 located at the interface of transmembrane segment M6 and the cytosol. Its replacement by Asn or Val (Petrov et al. (2000) J. Biol. Chem., 275, 15709-15716) or by Ala (Miranda et al. (2011) Biochim. Biophys. Acta, 1808, 1781-1789) caused complete blockage of biogenesis of the enzyme, which did not reach secretory vesicles. It was proposed that a strong ionic bond (salt bridge) could be formed between this residue and positively charged residue(s) in close proximity, and the replacement D739A disrupted this bond. Based on a 3D homology model of the enzyme, it was suggested that the conserved Arg811 located in close proximity to Asp739 could be such stabilizing residue. To test this suggestion, single mutants with substituted Asp739 (D739V, D739N, D739A, and D739R) and Arg811 (R811L, R811M, R811A, and R811D) as well as double mutants carrying charge-neutralizing (D739A/R811A) or charge-swapping (D739R/R811D) substitutions were used. Expression of ATPases with single substitutions R811A and R811D were 38-63%, and their activities were 29-30% of the wild type level; ATP hydrolysis and H+ transport in these enzymes were essentially uncoupled. For the other substitutions including the double mutations, the biogenesis of the enzyme was practically blocked. These data confirm the important role of Asp739 and Arg811 residues for the biogenesis and function of the enzyme, suggesting their importance for defining H+ transport determinants but ruling out, however, the existence of a strong ionic bond (salt bridge) between these two residues and/or importance of such bridge for structure-function relationships in Pma1 H+-ATPase.
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Affiliation(s)
- V V Petrov
- Skryabin Institute of Biochemistry and Physiology of Microorganisms, Pushchino, Moscow Region, 142290, Russia.
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17
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Li Y, Provenzano S, Bliek M, Spelt C, Appelhagen I, Machado de Faria L, Verweij W, Schubert A, Sagasser M, Seidel T, Weisshaar B, Koes R, Quattrocchio F. Evolution of tonoplast P-ATPase transporters involved in vacuolar acidification. THE NEW PHYTOLOGIST 2016; 211:1092-107. [PMID: 27214749 DOI: 10.1111/nph.14008] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 03/07/2016] [Indexed: 05/21/2023]
Abstract
Petunia mutants (Petunia hybrida) with blue flowers defined a novel vacuolar proton pump consisting of two interacting P-ATPases, PH1 and PH5, that hyper-acidify the vacuoles of petal cells. PH5 is similar to plasma membrane H(+) P3A -ATPase, whereas PH1 is the only known eukaryoticP3B -ATPase. As there were no indications that this tonoplast pump is widespread in plants, we investigated the distribution and evolution of PH1 and PH5. We combined database mining and phylogenetic and synteny analyses of PH1- and PH5-like proteins from all kingdoms with functional analyses (mutant complementation and intracellular localization) of homologs from diverse angiosperms. We identified functional PH1 and PH5 homologs in divergent angiosperms. PH5 homologs evolved from plasma membrane P3A -ATPases, acquiring an N-terminal tonoplast-sorting sequence and new cellular function before angiosperms appeared. PH1 is widespread among seed plants and related proteins are found in some groups of bacteria and fungi and in one moss, but is absent in most algae, suggesting that its evolution involved several cases of gene loss and possibly horizontal transfer events. The distribution of PH1 and PH5 in the plant kingdom suggests that vacuolar acidification by P-ATPases appeared in gymnosperms before flowers. This implies that, next to flower color determination, vacuolar hyper-acidification is required for yet unknown processes.
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Affiliation(s)
- Yanbang Li
- Department of Plant Development and (Epi)Genetics, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098XH, Amsterdam, the Netherlands
- Department of Molecular and Cell Biology, VU-University, De Boelelaan 1081, 1071 HK, Amsterdam, the Netherlands
| | - Sofia Provenzano
- Department of Plant Development and (Epi)Genetics, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098XH, Amsterdam, the Netherlands
- Department of Agricultural, Forestry and Food Sciences, University of Turin, 10095, Grugliasco, Italy
| | - Mattijs Bliek
- Department of Plant Development and (Epi)Genetics, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098XH, Amsterdam, the Netherlands
- Department of Molecular and Cell Biology, VU-University, De Boelelaan 1081, 1071 HK, Amsterdam, the Netherlands
| | - Cornelis Spelt
- Department of Plant Development and (Epi)Genetics, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098XH, Amsterdam, the Netherlands
- Department of Molecular and Cell Biology, VU-University, De Boelelaan 1081, 1071 HK, Amsterdam, the Netherlands
| | - Ingo Appelhagen
- Genome Research, Faculty of Biology, Bielefeld University, 33615, Bielefeld, Germany
| | - Laura Machado de Faria
- Department of Molecular and Cell Biology, VU-University, De Boelelaan 1081, 1071 HK, Amsterdam, the Netherlands
| | - Walter Verweij
- Department of Molecular and Cell Biology, VU-University, De Boelelaan 1081, 1071 HK, Amsterdam, the Netherlands
| | - Andrea Schubert
- Department of Agricultural, Forestry and Food Sciences, University of Turin, 10095, Grugliasco, Italy
| | - Martin Sagasser
- Genome Research, Faculty of Biology, Bielefeld University, 33615, Bielefeld, Germany
| | - Thorsten Seidel
- Dynamic Cell Imaging, Faculty of Biology, Bielefeld University, 33501, Bielefeld, Germany
| | - Bernd Weisshaar
- Genome Research, Faculty of Biology, Bielefeld University, 33615, Bielefeld, Germany
| | - Ronald Koes
- Department of Plant Development and (Epi)Genetics, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098XH, Amsterdam, the Netherlands
- Department of Molecular and Cell Biology, VU-University, De Boelelaan 1081, 1071 HK, Amsterdam, the Netherlands
| | - Francesca Quattrocchio
- Department of Plant Development and (Epi)Genetics, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098XH, Amsterdam, the Netherlands
- Department of Molecular and Cell Biology, VU-University, De Boelelaan 1081, 1071 HK, Amsterdam, the Netherlands
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18
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Veshaguri S, Christensen SM, Kemmer GC, Ghale G, Møller MP, Lohr C, Christensen AL, Justesen BH, Jørgensen IL, Schiller J, Hatzakis NS, Grabe M, Pomorski TG, Stamou D. Direct observation of proton pumping by a eukaryotic P-type ATPase. Science 2016; 351:1469-73. [PMID: 27013734 DOI: 10.1126/science.aad6429] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Accepted: 02/23/2016] [Indexed: 12/12/2022]
Abstract
In eukaryotes, P-type adenosine triphosphatases (ATPases) generate the plasma membrane potential and drive secondary transport systems; however, despite their importance, their regulation remains poorly understood. We monitored at the single-molecule level the activity of the prototypic proton-pumping P-type ATPase Arabidopsis thaliana isoform 2 (AHA2). Our measurements, combined with a physical nonequilibrium model of vesicle acidification, revealed that pumping is stochastically interrupted by long-lived (~100 seconds) inactive or leaky states. Allosteric regulation by pH gradients modulated the switch between these states but not the pumping or leakage rates. The autoinhibitory regulatory domain of AHA2 reduced the intrinsic pumping rates but increased the dwell time in the active pumping state. We anticipate that similar functional dynamics underlie the operation and regulation of many other active transporters.
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Affiliation(s)
- Salome Veshaguri
- Bionanotecnology and Nanomedicine Laboratory, University of Copenhagen, Copenhagen, Denmark. Department of Chemistry, University of Copenhagen, Copenhagen, Denmark. Nano-Science Center, University of Copenhagen, Copenhagen, Denmark. Lundbeck Foundation Center Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
| | - Sune M Christensen
- Bionanotecnology and Nanomedicine Laboratory, University of Copenhagen, Copenhagen, Denmark. Department of Chemistry, University of Copenhagen, Copenhagen, Denmark. Nano-Science Center, University of Copenhagen, Copenhagen, Denmark. Lundbeck Foundation Center Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
| | - Gerdi C Kemmer
- Centre for Membrane Pumps in Cells and Disease - PUMPKIN, Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg Denmark
| | - Garima Ghale
- Bionanotecnology and Nanomedicine Laboratory, University of Copenhagen, Copenhagen, Denmark. Department of Chemistry, University of Copenhagen, Copenhagen, Denmark. Nano-Science Center, University of Copenhagen, Copenhagen, Denmark. Lundbeck Foundation Center Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
| | - Mads P Møller
- Bionanotecnology and Nanomedicine Laboratory, University of Copenhagen, Copenhagen, Denmark. Department of Chemistry, University of Copenhagen, Copenhagen, Denmark. Nano-Science Center, University of Copenhagen, Copenhagen, Denmark. Lundbeck Foundation Center Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
| | - Christina Lohr
- Bionanotecnology and Nanomedicine Laboratory, University of Copenhagen, Copenhagen, Denmark. Department of Chemistry, University of Copenhagen, Copenhagen, Denmark. Nano-Science Center, University of Copenhagen, Copenhagen, Denmark. Lundbeck Foundation Center Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
| | - Andreas L Christensen
- Bionanotecnology and Nanomedicine Laboratory, University of Copenhagen, Copenhagen, Denmark. Department of Chemistry, University of Copenhagen, Copenhagen, Denmark. Nano-Science Center, University of Copenhagen, Copenhagen, Denmark. Lundbeck Foundation Center Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
| | - Bo H Justesen
- Centre for Membrane Pumps in Cells and Disease - PUMPKIN, Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg Denmark
| | - Ida L Jørgensen
- Centre for Membrane Pumps in Cells and Disease - PUMPKIN, Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg Denmark
| | - Jürgen Schiller
- Institute of Medical Physics and Biophysics, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Nikos S Hatzakis
- Bionanotecnology and Nanomedicine Laboratory, University of Copenhagen, Copenhagen, Denmark. Department of Chemistry, University of Copenhagen, Copenhagen, Denmark. Nano-Science Center, University of Copenhagen, Copenhagen, Denmark. Lundbeck Foundation Center Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
| | - Michael Grabe
- Cardiovascular Research Institute, Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94143, USA
| | - Thomas Günther Pomorski
- Centre for Membrane Pumps in Cells and Disease - PUMPKIN, Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg Denmark
| | - Dimitrios Stamou
- Bionanotecnology and Nanomedicine Laboratory, University of Copenhagen, Copenhagen, Denmark. Department of Chemistry, University of Copenhagen, Copenhagen, Denmark. Nano-Science Center, University of Copenhagen, Copenhagen, Denmark. Lundbeck Foundation Center Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
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19
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Subramani S, Perdreau-Dahl H, Morth JP. The magnesium transporter A is activated by cardiolipin and is highly sensitive to free magnesium in vitro. eLife 2016; 5. [PMID: 26780187 PMCID: PMC4758953 DOI: 10.7554/elife.11407] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2015] [Accepted: 01/16/2016] [Indexed: 01/19/2023] Open
Abstract
The magnesium transporter A (MgtA) is a specialized P-type ATPase, believed to import Mg2+ into the cytoplasm. In Salmonella typhimurium and Escherichia coli, the virulence determining two-component system PhoQ/PhoP regulates the transcription of mgtA gene by sensing Mg2+ concentrations in the periplasm. However, the factors that affect MgtA function are not known. This study demonstrates, for the first time, that MgtA is highly dependent on anionic phospholipids and in particular, cardiolipin. Colocalization studies confirm that MgtA is found in the cardiolipin lipid domains in the membrane. The head group of cardiolipin plays major role in activation of MgtA suggesting that cardiolipin may act as a Mg2+ chaperone for MgtA. We further show that MgtA is highly sensitive to free Mg2+ (Mg2+free) levels in the solution. MgtA is activated when the Mg2+free concentration is reduced below 10 μM and is strongly inhibited above 1 mM, indicating that Mg2+free acts as product inhibitor. Combined, our findings conclude that MgtA may act as a sensor as well as a transporter of Mg2+. DOI:http://dx.doi.org/10.7554/eLife.11407.001 Magnesium is an essential element for living cells, meaning that organisms from bacteria to humans need magnesium to survive. All cells are surrounded by a membrane made of fatty molecules called lipids, which is also embedded with proteins. Magnesium, like other metal ions, is transported inside cells across the cell’s membrane by specific membrane proteins. A species of gut bacteria called E. coli has two separate magnesium transport systems: one that works at high concentrations of magnesium and one at lower concentrations. The latter system involves a membrane protein called magnesium transporter A (or MgtA for short), which works like a molecular pump. However, it was not known exactly how this transporter was affected by magnesium nor how sensitive it was to this divalent metal ion. It was also unclear whether MgtA worked alone in the bacterial membrane or if it worked in conjunction with other molecules. Now Subramani et al. have managed to show that MgtA can sense magnesium ions down to micromolar concentrations, which is the equivalent to a pinch (1 gram) of magnesium salt in 10,000 liters of water. The experiments also showed that this detection system depended on a specific lipid molecule in the membrane called cardiolipin. MgtA and cardiolipin were found together in the membrane of living E. coli suggesting that the two do indeed work together. The discovery that a membrane transporter that pumps ions needs cardiolipin to work suggests that cells could indirectly control the movement of ions by changing the levels of specific lipids in their membranes. Subramani et al. now hope to use techniques, such as X-ray crystallography, to visualize how magnesium and cardiolipin bind to MtgA and explore how the three molecules work together as a complete system. Information about these interactions could in the future help researchers understand how these bacteria try to protect themself in the hostile environment in the human gut or cells of the immune systems. Further studies of this system could be used to develop biological sensors for magnesium or to design antibiotics that interfere with the magnesium transporter to treat bacterial infections. DOI:http://dx.doi.org/10.7554/eLife.11407.002
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Affiliation(s)
- Saranya Subramani
- Norwegian Centre of Molecular Medicine, Nordic EMBL Partnership University of Oslo, Oslo, Norway
| | - Harmonie Perdreau-Dahl
- Norwegian Centre of Molecular Medicine, Nordic EMBL Partnership University of Oslo, Oslo, Norway.,Institute for Experimental Medical Research, Oslo University Hospital, Oslo, Norway
| | - Jens Preben Morth
- Norwegian Centre of Molecular Medicine, Nordic EMBL Partnership University of Oslo, Oslo, Norway.,Institute for Experimental Medical Research, Oslo University Hospital, Oslo, Norway
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20
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Guerra F, Bondar AN. Dynamics of the Plasma Membrane Proton Pump. J Membr Biol 2014; 248:443-53. [DOI: 10.1007/s00232-014-9732-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2014] [Accepted: 09/18/2014] [Indexed: 12/01/2022]
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21
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Justesen BH, Hansen RW, Martens HJ, Theorin L, Palmgren MG, Martinez KL, Pomorski TG, Fuglsang AT. Active plasma membrane P-type H+-ATPase reconstituted into nanodiscs is a monomer. J Biol Chem 2013; 288:26419-29. [PMID: 23836891 DOI: 10.1074/jbc.m112.446948] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Plasma membrane H(+)-ATPases form a subfamily of P-type ATPases responsible for pumping protons out of cells and are essential for establishing and maintaining the crucial transmembrane proton gradient in plants and fungi. Here, we report the reconstitution of the Arabidopsis thaliana plasma membrane H(+)-ATPase isoform 2 into soluble nanoscale lipid bilayers, also termed nanodiscs. Based on native gel analysis and cross-linking studies, the pump inserts into nanodiscs as a functional monomer. Insertion of the H(+)-ATPase into nanodiscs has the potential to enable structural and functional characterization using techniques normally applicable only for soluble proteins.
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22
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Ekberg K, Wielandt AG, Buch-Pedersen MJ, Palmgren MG. A conserved asparagine in a P-type proton pump is required for efficient gating of protons. J Biol Chem 2013; 288:9610-9618. [PMID: 23420846 DOI: 10.1074/jbc.m112.417345] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The minimal proton pumping machinery of the Arabidopsis thaliana P-type plasma membrane H(+)-ATPase isoform 2 (AHA2) consists of an aspartate residue serving as key proton donor/acceptor (Asp-684) and an arginine residue controlling the pKa of the aspartate. However, other important aspects of the proton transport mechanism such as gating, and the ability to occlude protons, are still unclear. An asparagine residue (Asn-106) in transmembrane segment 2 of AHA2 is conserved in all P-type plasma membrane H(+)-ATPases. In the crystal structure of the plant plasma membrane H(+)-ATPase, this residue is located in the putative ligand entrance pathway, in close proximity to the central proton donor/acceptor Asp-684. Substitution of Asn-106 resulted in mutant enzymes with significantly reduced ability to transport protons against a membrane potential. Sensitivity toward orthovanadate was increased when Asn-106 was substituted with an aspartate residue, but decreased in mutants with alanine, lysine, glutamine, or threonine replacement of Asn-106. The apparent proton affinity was decreased for all mutants, most likely due to a perturbation of the local environment of Asp-684. Altogether, our results demonstrate that Asn-106 is important for closure of the proton entrance pathway prior to proton translocation across the membrane.
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Affiliation(s)
- Kira Ekberg
- Department of Plant and Environmental Sciences, Centre for Membrane Pumps in Cells and Disease-PUMPKIN, Danish National Research Foundation, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg, Denmark
| | - Alex G Wielandt
- Department of Plant and Environmental Sciences, Centre for Membrane Pumps in Cells and Disease-PUMPKIN, Danish National Research Foundation, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg, Denmark
| | - Morten J Buch-Pedersen
- Department of Plant and Environmental Sciences, Centre for Membrane Pumps in Cells and Disease-PUMPKIN, Danish National Research Foundation, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg, Denmark
| | - Michael G Palmgren
- Department of Plant and Environmental Sciences, Centre for Membrane Pumps in Cells and Disease-PUMPKIN, Danish National Research Foundation, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg, Denmark.
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23
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Rudashevskaya EL, Ye J, Jensen ON, Fuglsang AT, Palmgren MG. Phosphosite mapping of P-type plasma membrane H+-ATPase in homologous and heterologous environments. J Biol Chem 2011; 287:4904-13. [PMID: 22174420 DOI: 10.1074/jbc.m111.307264] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Phosphorylation is an important posttranslational modification of proteins in living cells and primarily serves regulatory purposes. Several methods were employed for isolating phosphopeptides from proteolytically digested plasma membranes of Arabidopsis thaliana. After a mass spectrometric analysis of the resulting peptides we could identify 10 different phosphorylation sites in plasma membrane H(+)-ATPases AHA1, AHA2, AHA3, and AHA4/11, five of which have not been reported before, bringing the total number of phosphosites up to 11, which is substantially higher than reported so far for any other P-type ATPase. Phosphosites were almost exclusively (9 of 10) in the terminal regulatory domains of the pumps. The AHA2 isoform was subsequently expressed in the yeast Saccharomyces cerevisiae. The plant protein was phosphorylated at multiple sites in yeast, and surprisingly, seven of nine of the phosphosites identified in AHA2 were identical in the plant and fungal systems even though none of the target sequences in AHA2 show homology to proteins of the fungal host. These findings suggest an unexpected accessibility of the terminal regulatory domain of plasma membrane H(+)-ATPase to protein kinase action.
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Affiliation(s)
- Elena L Rudashevskaya
- Centre for Membrane Pumps in Cells and Disease-PUMPkin, Department of Plant Biology and Biotechnology, University of Copenhagen, DK-1871 Frederiksberg C, Denmark.
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24
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Affiliation(s)
- Michael G. Palmgren
- Center for Membrane Pumps in Cells and Disease – PUMPKIN, Danish National Research Foundation, University of Copenhagen, DK-1871 Frederiksberg C, Denmark;
| | - Poul Nissen
- Center for Membrane Pumps in Cells and Disease – PUMPKIN, Danish National Research Foundation, Aarhus University, DK-8000 Århus C, Denmark;
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25
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Miranda M, Pardo JP, Petrov VV. Structure-function relationships in membrane segment 6 of the yeast plasma membrane Pma1 H(+)-ATPase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:1781-9. [PMID: 21156155 DOI: 10.1016/j.bbamem.2010.11.034] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2010] [Revised: 11/24/2010] [Accepted: 11/30/2010] [Indexed: 11/30/2022]
Abstract
The crystal structures of the Ca(2+)- and H(+)-ATPases shed light into the membrane embedded domains involved in binding and ion translocation. Consistent with site-directed mutagenesis, these structures provided additional evidence that membrane-spanning segments M4, M5, M6 and M8 are the core through which cations are pumped. In the present study, we have used alanine/serine scanning mutagenesis to study the structure-function relationships within M6 (Leu-721-Pro-742) of the yeast plasma membrane ATPase. Of the 22 mutants expressed and analyzed in secretory vesicles, alanine substitutions at two well conserved residues (Asp-730 and Asp-739) led to a complete block in biogenesis; in the mammalian P-ATPases, residues corresponding to Asp-730 are part of the cation-binding domain. Two other mutants (V723A and I736A) displayed a dramatic 20-fold increase in the IC(50) for inorganic orthovanadate compared to the wild-type control, accompanied by a significant reduction in the K(m) for Mg-ATP, and an alkaline shift in the pH optimum for ATP hydrolysis. This behavior is apparently due to a shift in equilibrium from the E(2) conformation of the ATPase towards the E(1) conformation. By contrast, the most striking mutants lying toward the extracellular side in a helical structure (L721A, I722A, F724A, I725A, I727A and F728A) were expressed in secretory vesicles but had a severe reduction of ATPase activity. Moreover, all of these mutants but one (F728A) were unable to support yeast growth when the wild-type chromosomal PMA1 gene was replaced by the mutant allele. Surprisingly, in contrast to M8 where mutations S800A and E803Q (Guerra et al., Biochim. Biophys. Acta 1768: 2383-2392, 2007) led to a dramatic increase in the apparent stoichiometry of H(+) transport, three substitutions (A726S, A732S and T733A) in M6 showed a reduction in the apparent coupling ratio. Taken together, these results suggest that M6 residues play an important role in protein stability and function, and probably are responsible for cation binding and stoichiometry of ion transport as suggested by homology modeling.
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Affiliation(s)
- Manuel Miranda
- Department of Biological Sciences, University of Texas, El Paso, TX 79968, USA.
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26
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In and out of the cation pumps: P-type ATPase structure revisited. Curr Opin Struct Biol 2010; 20:431-9. [PMID: 20634056 DOI: 10.1016/j.sbi.2010.06.007] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2010] [Revised: 06/08/2010] [Accepted: 06/15/2010] [Indexed: 12/12/2022]
Abstract
Active transport across membranes is a crucial requirement for life. P-type ATPases build up electrochemical gradients at the expense of ATP by forming and splitting a covalent phosphoenzyme intermediate, coupled to conformational changes in the transmembrane section where the ions are translocated. The marked increment during the last three years in the number of crystal structures of P-type ATPases has greatly improved our understanding of the similarities and differences of pumps with different ion specificities, since the structures of the Ca2+-ATPase, the Na+,K+-ATPase and the H+-ATPase can now be compared directly. Mechanisms for ion gating, charge neutralization and backflow prevention are starting to emerge from comparative structural analysis; and in combination with functional studies of mutated pumps this provides a framework for speculating on how the ions are bound and released as well as on how specificity is achieved.
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Protons and how they are transported by proton pumps. Pflugers Arch 2008; 457:573-9. [DOI: 10.1007/s00424-008-0503-8] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2008] [Revised: 03/17/2008] [Accepted: 03/21/2008] [Indexed: 12/01/2022]
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Certal AC, Almeida RB, Carvalho LM, Wong E, Moreno N, Michard E, Carneiro J, Rodriguéz-Léon J, Wu HM, Cheung AY, Feijó JA. Exclusion of a proton ATPase from the apical membrane is associated with cell polarity and tip growth in Nicotiana tabacum pollen tubes. THE PLANT CELL 2008; 20:614-34. [PMID: 18364468 PMCID: PMC2329945 DOI: 10.1105/tpc.106.047423] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2006] [Revised: 02/13/2008] [Accepted: 02/29/2008] [Indexed: 05/18/2023]
Abstract
Polarized growth in pollen tubes results from exocytosis at the tip and is associated with conspicuous polarization of Ca(2+), H(+), K(+), and Cl(-) -fluxes. Here, we show that cell polarity in Nicotiana tabacum pollen is associated with the exclusion of a novel pollen-specific H(+)-ATPase, Nt AHA, from the growing apex. Nt AHA colocalizes with extracellular H(+) effluxes, which revert to influxes where Nt AHA is absent. Fluorescence recovery after photobleaching analysis showed that Nt AHA moves toward the apex of growing pollen tubes, suggesting that the major mechanism of insertion is not through apical exocytosis. Nt AHA mRNA is also excluded from the tip, suggesting a mechanism of polarization acting at the level of translation. Localized applications of the cation ionophore gramicidin A had no effect where Nt AHA was present but acidified the cytosol and induced reorientation of the pollen tube where Nt AHA was absent. Transgenic pollen overexpressing Nt AHA-GFP developed abnormal callose plugs accompanied by abnormal H(+) flux profiles. Furthermore, there is no net flux of H(+) in defined patches of membrane where callose plugs are to be formed. Taken together, our results suggest that proton dynamics may underlie basic mechanisms of polarity and spatial regulation in growing pollen tubes.
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Affiliation(s)
- Ana C Certal
- Instituto Gulbenkian de Ciência, Centro de Biologia do Desenvolvimento, 2780-156 Oeiras, Portugal
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Crystal structure of the plasma membrane proton pump. Nature 2007; 450:1111-4. [PMID: 18075595 DOI: 10.1038/nature06417] [Citation(s) in RCA: 273] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2007] [Accepted: 10/26/2007] [Indexed: 11/08/2022]
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Hsiao YY, Pan YJ, Hsu SH, Huang YT, Liu TH, Lee CH, Lee CH, Liu PF, Chang WC, Wang YK, Chien LF, Pan RL. Functional roles of arginine residues in mung bean vacuolar H+-pyrophosphatase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2007; 1767:965-73. [PMID: 17543272 DOI: 10.1016/j.bbabio.2007.04.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2007] [Revised: 04/26/2007] [Accepted: 04/27/2007] [Indexed: 10/23/2022]
Abstract
Plant vacuolar H+-translocating inorganic pyrophosphatase (V-PPase EC 3.6.1.1) utilizes inorganic pyrophosphate (PPi) as an energy source to generate a H+ gradient potential for the secondary transport of ions and metabolites across the vacuole membrane. In this study, functional roles of arginine residues in mung bean V-PPase were determined by site-directed mutagenesis. Alignment of amino-acid sequence of K+-dependent V-PPases from several organisms showed that 11 of all 15 arginine residues were highly conserved. Arginine residues were individually substituted by alanine residues to produce R-->A-substituted V-PPases, which were then heterologously expressed in yeast. The characteristics of mutant variants were subsequently scrutinized. As a result, most R-->A-substituted V-PPases exhibited similar enzymatic activities to the wild-type with exception that R242A, R523A, and R609A mutants markedly lost their abilities of PPi hydrolysis and associated H+-translocation. Moreover, mutation on these three arginines altered the optimal pH and significantly reduced K+-stimulation for enzymatic activities, implying a conformational change or a modification in enzymatic reaction upon substitution. In particular, R242A performed striking resistance to specific arginine-modifiers, 2,3-butanedione and phenylglyoxal, revealing that Arg242 is most likely the primary target residue for these two reagents. The mutation at Arg242 also removed F- inhibition that is presumably derived from the interfering in the formation of substrate complex Mg2+-PPi. Our results suggest accordingly that active pocket of V-PPase probably contains the essential Arg242 which is embedded in a more hydrophobic environment.
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Affiliation(s)
- Yi-Yuong Hsiao
- Department of Life Sciences and Institute of Bioinformatics and Structural Biology, College of Life Sciences, National Tsing Hua University, Hsin Chu 30043, Taiwan
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Guerra G, Petrov VV, Allen KE, Miranda M, Pardo JP, Slayman CW. Role of transmembrane segment M8 in the biogenesis and function of yeast plasma-membrane H(+)-ATPase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:2383-92. [PMID: 17573037 PMCID: PMC2267258 DOI: 10.1016/j.bbamem.2007.04.029] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2007] [Revised: 04/26/2007] [Accepted: 04/27/2007] [Indexed: 11/20/2022]
Abstract
Of the four transmembrane helices (M4, M5, M6, and M8) that pack together to form the ion-binding sites of P(2)-type ATPases, M8 has until now received the least attention. The present study has used alanine-scanning mutagenesis to map structure-function relationships throughout M8 of the yeast plasma-membrane H(+)-ATPase. Mutant forms of the ATPase were expressed in secretory vesicles and at the plasma membrane for measurements of ATP hydrolysis and ATP-dependent H(+) pumping. In secretory vesicles, Ala substitutions at a cluster of four positions near the extracytoplasmic end of M8 led to partial uncoupling of H(+) transport from ATP hydrolysis, while substitution of Ser-800 (close to the middle of M8) by Ala increased the apparent stoichiometry of H(+) transport. A similar increase has previously been reported following the substitution of Glu-803 by Gln (Petrov, V. et al., J. Biol. Chem. 275:15709-15718, 2000) at a position known to contribute directly to Ca(2+) binding in the Ca(2+)-ATPase of sarcoplasmic reticulum (Toyoshima, C., et al., Nature 405: 647-655, 2000). Four other mutations in M8 interfered with H(+)-ATPase folding and trafficking to the plasma membrane; based on homology modeling, they occupy positions that appear important for the proper bundling of M8 with M5, M6, M7, and M10. Taken together, these results point to a key role for M8 in the biogenesis, stability, and physiological functioning of the H(+)-ATPase.
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Affiliation(s)
| | | | | | | | | | - Carolyn W. Slayman
- To whom reprint requests should be addressed: Department of Genetics, Yale University School of Medicine, 333 Cedar Street, New Haven CT 06510; tel. (203) 737-1770; fax (203) 737-1771; e-mail,
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Buch-Pedersen MJ, Rudashevskaya EL, Berner TS, Venema K, Palmgren MG. Potassium as an intrinsic uncoupler of the plasma membrane H+-ATPase. J Biol Chem 2006; 281:38285-92. [PMID: 17056603 DOI: 10.1074/jbc.m604781200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The plant plasma membrane proton pump (H(+)-ATPase) is stimulated by potassium, but it has remained unclear whether potassium is actually transported by the pump or whether it serves other roles. We now show that K(+) is bound to the proton pump at a site involving Asp(617) in the cytoplasmic phosphorylation domain, from where it is unlikely to be transported. Binding of K(+) to this site can induce dephosphorylation of the phosphorylated E(1)P reaction cycle intermediate by a mechanism involving Glu(184) in the conserved TGES motif of the pump actuator domain. Our data identify K(+) as an intrinsic uncoupler of the proton pump and suggest a mechanism for control of the H(+)/ATP coupling ratio. K(+)-induced dephosphorylation of E(1)P may serve regulatory purposes and play a role in negative regulation of the transmembrane electrochemical gradient under cellular conditions where E(1)P is accumulating.
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Affiliation(s)
- Morten J Buch-Pedersen
- Department of Plant Biology, The Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Copenhagen, Denmark.
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Okkeri J, Haltia T. The metal-binding sites of the zinc-transporting P-type ATPase of Escherichia coli. Lys693 and Asp714 in the seventh and eighth transmembrane segments of ZntA contribute to the coupling of metal binding and ATPase activity. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2006; 1757:1485-95. [PMID: 16890908 DOI: 10.1016/j.bbabio.2006.06.008] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2006] [Revised: 06/08/2006] [Accepted: 06/15/2006] [Indexed: 10/24/2022]
Abstract
ZntA is a P-type ATPase which transports Zn(2+), Pb(2+) and Cd(2+) out of the cell. Two cysteine-containing motifs, CAAC near the N-terminus and CPC in transmembrane helix 6, are involved in binding of the translocated metal. We have studied these motifs by mutating the cysteines to serines. The roles of two other possible metal-binding residues, K(693) and D(714), in transmembrane helices 7 and 8, were also addressed. The mutation CAAC-->SAAS reduces the ATPase activity by 50%. The SAAS mutant is phosphorylated with ATP almost as efficiently as the wild type. However, its phosphorylation with P(i) is poorer than that of the wild type and its dephosphorylation rate is faster than that of the wild type ATPase. The CPC-->SPS mutant is inactive but residual phosphorylation with ATP could still be observed. The most important findings of this work deal with the prospective metal-binding residues K(693) and D(714): the substitution K693N eliminates the Zn(2+)-stimulated ATPase activity completely, although significant Zn(2+)-dependent phosphorylation by ATP remains. The K693N ATPase is hyperphosphorylated by P(i). ZntA carrying the change D714M has strong metal-independent ATPase activity and is very weakly phosphorylated both by ATP and P(i). In conclusion, K(693) and D(714) are functionally essential and appear to contribute to the metal specificity of ZntA, most probably by being parts of the metal-binding site made up by the CPC motif.
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Affiliation(s)
- Juha Okkeri
- Institute of Biomedical Sciences/Biochemistry, P. O. Box 63 (Biomedicum Helsinki, Haartmaninkatu 8), FIN-00014 University of Helsinki, Helsinki, Finland.
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Fraysse AS, Møller ALB, Poulsen LR, Wollenweber B, Buch-Pedersen MJ, Palmgren MG. A systematic mutagenesis study of Ile-282 in transmembrane segment M4 of the plasma membrane H+-ATPase. J Biol Chem 2005; 280:21785-90. [PMID: 15829483 DOI: 10.1074/jbc.m413091200] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Homology models of plasma membrane H(+)-ATPase (Bukrinsky, J. T., Buch-Pedersen, M. J., Larsen, S., and Palmgren, M. G. (2001) FEBS Lett. 494, 6-10) has pointed to residues in transmembrane segment M4 as being important for proton translocation by P-type proton pumps. To test this model, alanine-scanning mutagenesis was carried out through 12 residues in the M4 of the plant plasma membrane H(+)-ATPase AHA2. An I282A mutation showed apparent reduced H(+) affinity, and this residue was subsequently substituted with all other naturally occurring amino acids by saturation mutagenesis. The ability of mutant enzymes to substitute for the yeast proton pump PMA1 was found to correlate with the size of the side chain rather than its chemical nature. Thus, smaller side chains (Gly, Ala, and Ser) at this position resulted in lower H(+) affinity and lowered levels of H(+) transport in vivo, whereas substitution with side chains of similar and larger size resulted in only minor effects. Substitutions of Ile-282 had only minor effects on ATP affinity and sensitivity toward vanadate, ruling out an indirect effect through changes in the enzyme conformational equilibrium. These results are consistent with a model in which the backbone carbonyl oxygen of Ile-282 contributes directly to proton translocation.
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Affiliation(s)
- A Staffan Fraysse
- Department of Plant Biology, The Royal Danish Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark
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