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Heger T, Zatloukal M, Kubala M, Strnad M, Gruz J. Procyanidin C1 from Viola odorata L. inhibits Na +,K +-ATPase. Sci Rep 2022; 12:7011. [PMID: 35487935 PMCID: PMC9055044 DOI: 10.1038/s41598-022-11086-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 04/13/2022] [Indexed: 01/30/2023] Open
Abstract
Members of the Viola genus play important roles in traditional Asian herbal medicine. This study investigates the ability of Viola odorata L. extracts to inhibit Na+,K+-ATPase, an essential animal enzyme responsible for membrane potential maintenance. The root extract of V. odorata strongly inhibited Na+,K+-ATPase, while leaf and seeds extracts were basically inactive. A UHPLC-QTOF-MS/MS metabolomic approach was used to identify the chemical principle of the root extract’s activity, resulting in the detection of 35,292 features. Candidate active compounds were selected by correlating feature area with inhibitory activity in 14 isolated fractions. This yielded a set of 15 candidate compounds, of which 14 were preliminarily identified as procyanidins. Commercially available procyanidins (B1, B2, B3 and C1) were therefore purchased and their ability to inhibit Na+,K+-ATPase was investigated. Dimeric procyanidins B1, B2 and B3 were found to be inactive, but the trimeric procyanidin C1 strongly inhibited Na+,K+-ATPase with an IC50 of 4.5 µM. This newly discovered inhibitor was docked into crystal structures mimicking the Na3E1∼P·ADP and K2E2·Pi states to identify potential interaction sites within Na+,K+-ATPase. Possible binding mechanisms and the principle responsible for the observed root extract activity are discussed.
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Affiliation(s)
- Tomas Heger
- Department of Experimental Biology, Faculty of Science, Palacky University, Olomouc, Czech Republic
| | - Marek Zatloukal
- Department of Chemical Biology, Faculty of Science, Palacky University, Olomouc, Czech Republic
| | - Martin Kubala
- Department of Experimental Physics, Faculty of Science, Palacky University, Olomouc, Czech Republic
| | - Miroslav Strnad
- Laboratory of Growth Regulators, Institute of Experimental Botany of the Czech Academy of Sciences, Palacky University, Olomouc, Czech Republic
| | - Jiri Gruz
- Department of Experimental Biology, Faculty of Science, Palacky University, Olomouc, Czech Republic.
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2
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RH421 binds into the ATP-binding site on the Na +/K +-ATPase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:2113-2122. [PMID: 28774819 DOI: 10.1016/j.bbamem.2017.07.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Revised: 07/28/2017] [Accepted: 07/30/2017] [Indexed: 11/22/2022]
Abstract
The Na+/K+-ATPase plays a key role in ion transport across the plasma membrane of all animal cells. The voltage-sensitive styrylpyrimidium dye RH421 has been used in several laboratories for monitoring of Na+/K+-ATPase kinetics. It is known, that RH421 can interact with the enzyme and it can influence its activity at micromolar concentrations, but structural details of this interaction are only poorly understood. Experiments with isolated large cytoplasmic loop (C45) of Na+/K+-ATPase revealed that RH421 can interact with this part of the protein with dissociation constant 1μM. The Trp-to-RH421 FRET performed on six single-tryptophan mutants revealed that RH421 binds directly into the ATP-binding site. This conclusion was further supported by results from molecular docking, site-directed mutagenesis and by competitive experiments using ATP. Experiments with C45/DPPC mixture revealed that RH421 can bind to both C45 and lipids, but only the former interaction was influenced by the presence of ATP.
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3
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Kubala M, Čechová P, Geletičová J, Biler M, Štenclová T, Trouillas P, Biedermann D. Flavonolignans As a Novel Class of Sodium Pump Inhibitors. Front Physiol 2016; 7:115. [PMID: 27065883 PMCID: PMC4812144 DOI: 10.3389/fphys.2016.00115] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Accepted: 03/14/2016] [Indexed: 11/13/2022] Open
Abstract
We examined the inhibitory effects of three flavonolignans and their dehydro- derivatives, taxifolin and quercetin on the activity of the Na+/K+-ATPase (NKA). The flavonolignans silychristin, dehydrosilychristin and dehydrosilydianin inhibited NKA with IC50 of 110 ± 40 μM, 38 ± 8 μM, and 36 ± 14 μM, respectively. Using the methods of molecular modeling, we identified several possible binding sites for these species on NKA and proposed the possible mechanisms of inhibition. The binding to the extracellular- or cytoplasmic C-terminal sites can block the transport of cations through the plasma membrane, while the binding on the interface of cytoplasmic domains can inhibit the enzyme allosterically. Fluorescence spectroscopy experiments confirmed the interaction of these three species with the large cytoplasmic segment connecting transmembrane helices 4 and 5 (C45). The flavonolignans are distinct from the cardiac glycosides that are currently used in NKA treatment. Because their binding sites are different, the mechanism of inhibition is different as well as the range of active concentrations, one can expect that these new NKA inhibitors would exhibit also a different biomedical actions than cardiac glycosides.
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Affiliation(s)
- Martin Kubala
- Department of Biophysics, Faculty of Science, Centre of Region Haná for Biotechnological and Agricultural Research, Palacký University Olomouc, Czech Republic
| | - Petra Čechová
- Department of Biophysics, Faculty of Science, Centre of Region Haná for Biotechnological and Agricultural Research, Palacký University Olomouc, Czech Republic
| | - Jaroslava Geletičová
- Department of Biophysics, Faculty of Science, Centre of Region Haná for Biotechnological and Agricultural Research, Palacký University Olomouc, Czech Republic
| | - Michal Biler
- Department of Biophysics, Faculty of Science, Centre of Region Haná for Biotechnological and Agricultural Research, Palacký UniversityOlomouc, Czech Republic; INSERM UMR 850, School of Pharmacy, University LimogesLimoges, France
| | - Tereza Štenclová
- Department of Biophysics, Faculty of Science, Centre of Region Haná for Biotechnological and Agricultural Research, Palacký University Olomouc, Czech Republic
| | - Patrick Trouillas
- INSERM UMR 850, School of Pharmacy, University LimogesLimoges, France; Department of Physical Chemistry, Faculty of Science, Regional Centre of Advanced Technologies and Materials, Palacký UniversityOlomouc, Czech Republic
| | - David Biedermann
- Laboratory of Biotransformation, Institute of Microbiology, Czech Academy of Sciences Prague, Czech Republic
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4
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Vacek J, Zatloukalova M, Geleticova J, Kubala M, Modriansky M, Fekete L, Masek J, Hubatka F, Turanek J. Electrochemical Platform for the Detection of Transmembrane Proteins Reconstituted into Liposomes. Anal Chem 2016; 88:4548-56. [DOI: 10.1021/acs.analchem.6b00618] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Jan Vacek
- Department
of Medical Chemistry and Biochemistry, Faculty of Medicine and Dentistry, Palacky University, Hnevotinska 3, 775 15 Olomouc, Czech Republic
| | - Martina Zatloukalova
- Department
of Medical Chemistry and Biochemistry, Faculty of Medicine and Dentistry, Palacky University, Hnevotinska 3, 775 15 Olomouc, Czech Republic
| | - Jaroslava Geleticova
- Department
of Biophysics, Centre of the Region Hana for Biotechnological and
Agricultural Research, Faculty of Science, Palacky University, Slechtitelu 27, 783 71 Olomouc, Czech Republic
| | - Martin Kubala
- Department
of Biophysics, Centre of the Region Hana for Biotechnological and
Agricultural Research, Faculty of Science, Palacky University, Slechtitelu 27, 783 71 Olomouc, Czech Republic
| | - Martin Modriansky
- Department
of Medical Chemistry and Biochemistry, Faculty of Medicine and Dentistry, Palacky University, Hnevotinska 3, 775 15 Olomouc, Czech Republic
| | - Ladislav Fekete
- Institute
of Physics, Academy of Sciences of the Czech Republic, Na Slovance
2, 18221 Prague, Czech Republic
| | - Josef Masek
- Department
of Pharmacology and Immunotherapy, Veterinary Research Institute, v.v.i.,
Hudcova 70, 621 00 Brno, Czech Republic
| | - Frantisek Hubatka
- Department
of Pharmacology and Immunotherapy, Veterinary Research Institute, v.v.i.,
Hudcova 70, 621 00 Brno, Czech Republic
| | - Jaroslav Turanek
- Department
of Pharmacology and Immunotherapy, Veterinary Research Institute, v.v.i.,
Hudcova 70, 621 00 Brno, Czech Republic
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5
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Geer MA, Fitzgerald MC. Characterization of the Saccharomyces cerevisiae ATP-Interactome using the iTRAQ-SPROX Technique. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2016; 27:233-243. [PMID: 26530046 DOI: 10.1007/s13361-015-1290-z] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Revised: 09/01/2015] [Accepted: 10/05/2015] [Indexed: 06/05/2023]
Abstract
The stability of proteins from rates of oxidation (SPROX) technique was used in combination with an isobaric mass tagging strategy to identify adenosine triphosphate (ATP) interacting proteins in the Saccharomyces cerevisiae proteome. The SPROX methodology utilized in this work enabled 373 proteins in a yeast cell lysate to be assayed for ATP interactions (both direct and indirect) using the non-hydrolyzable ATP analog, adenylyl imidodiphosphate (AMP-PNP). A total of 28 proteins were identified with AMP-PNP-induced thermodynamic stability changes. These protein hits included 14 proteins that were previously annotated as ATP-binding proteins in the Saccharomyces Genome Database (SGD). The 14 non-annotated ATP-binding proteins included nine proteins that were previously found to be ATP-sensitive in an earlier SPROX study using a stable isotope labeling with amino acids in cell culture (SILAC)-based approach. A bioinformatics analysis of the protein hits identified here and in the earlier SILAC-SPROX experiments revealed that many of the previously annotated ATP-binding protein hits were kinases, ligases, and chaperones. In contrast, many of the newly discovered ATP-sensitive proteins were not from these protein classes, but rather were hydrolases, oxidoreductases, and nucleic acid-binding proteins. Graphical Abstract ᅟ.
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Affiliation(s)
- M Ariel Geer
- Department of Chemistry, Duke University, Durham, NC, 27708-0346, USA
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6
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Vacek J, Zatloukalova M, Havlikova M, Ulrichova J, Kubala M. Changes in the intrinsic electrocatalytic nature of Na+/K+ ATPase reflect structural changes on ATP-binding: Electrochemical label-free approach. Electrochem commun 2013. [DOI: 10.1016/j.elecom.2012.11.020] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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7
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Zatloukalová M, Orolinová E, Kubala M, Hrbáč J, Vacek J. Electrochemical Determination of Transmembrane Protein Na+/K+-ATPase and Its Cytoplasmic Loop C45. ELECTROANAL 2012. [DOI: 10.1002/elan.201200165] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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8
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Hercend C, Bauvais C, Bollot G, Delacotte N, Chappuis P, Woimant F, Launay JM, Manivet P. Elucidation of the ATP7B N-domain Mg2+-ATP coordination site and its allosteric regulation. PLoS One 2011; 6:e26245. [PMID: 22046264 PMCID: PMC3203118 DOI: 10.1371/journal.pone.0026245] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2011] [Accepted: 09/23/2011] [Indexed: 11/25/2022] Open
Abstract
The diagnostic of orphan genetic disease is often a puzzling task as less attention is paid to the elucidation of the pathophysiology of these rare disorders at the molecular level. We present here a multidisciplinary approach using molecular modeling tools and surface plasmonic resonance to study the function of the ATP7B protein, which is impaired in the Wilson disease. Experimentally validated in silico models allow the elucidation in the Nucleotide binding domain (N-domain) of the Mg2+-ATP coordination site and answer to the controversial role of the Mg2+ ion in the nucleotide binding process. The analysis of protein motions revealed a substantial effect on a long flexible loop branched to the N-domain protein core. We demonstrated the capacity of the loop to disrupt the interaction between Mg2+-ATP complex and the N-domain and propose a role for this loop in the allosteric regulation of the nucleotide binding process.
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Affiliation(s)
- Claude Hercend
- APHP, Hôpital Lariboisière, Service de Biochimie et de Biologie Moléculaire, Paris, France
- INSERM U942, Biomarqueurs et Insuffisance cardiaque, Hôpital Lariboisière, Paris, France
| | - Cyril Bauvais
- Division of Structural Biology, Bioquanta, Paris, France
| | | | | | - Philippe Chappuis
- APHP, Hôpital Lariboisière, Service de Biochimie et de Biologie Moléculaire, Paris, France
| | - France Woimant
- APHP, Hôpital Lariboisière, Service de Neurologie, Paris, France
| | - Jean-Marie Launay
- APHP, Hôpital Lariboisière, Service de Biochimie et de Biologie Moléculaire, Paris, France
- INSERM U942, Biomarqueurs et Insuffisance cardiaque, Hôpital Lariboisière, Paris, France
| | - Philippe Manivet
- APHP, Hôpital Lariboisière, Service de Biochimie et de Biologie Moléculaire, Paris, France
- INSERM U829, SABNP Laboratory, Evry, France
- Université Evry Val-d'Essonne, Evry, France
- * E-mail:
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9
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Satoh K, Matsu-Ura T, Enomoto M, Nakamura H, Michikawa T, Mikoshiba K. Highly cooperative dependence of sarco/endoplasmic reticulum calcium ATPase SERCA2a pump activity on cytosolic calcium in living cells. J Biol Chem 2011; 286:20591-9. [PMID: 21515674 DOI: 10.1074/jbc.m110.204685] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Sarco/endoplasmic reticulum (SR/ER) Ca(2+)-ATPase (SERCA) is an intracellular Ca(2+) pump localized on the SR/ER membrane. The role of SERCA in refilling intracellular Ca(2+) stores is pivotal for maintaining intracellular Ca(2+) homeostasis, and disturbed SERCA activity causes many disease phenotypes, including heart failure, diabetes, cancer, and Alzheimer disease. Although SERCA activity has been described using a simple enzyme activity equation, the dynamics of SERCA activity in living cells is still unknown. To monitor SERCA activity in living cells, we constructed an enhanced CFP (ECFP)- and FlAsH-tagged SERCA2a, designated F-L577, which retains the ATP-dependent Ca(2+) pump activity. The FRET efficiency between ECFP and FlAsH of F-L577 is dependent on the conformational state of the molecule. ER luminal Ca(2+) imaging confirmed that the FRET signal changes directly reflect the Ca(2+) pump activity. Dual imaging of cytosolic Ca(2+) and the FRET signals of F-L577 in intact COS7 cells revealed that SERCA2a activity is coincident with the oscillatory cytosolic Ca(2+) concentration changes evoked by ATP stimulation. The Ca(2+) pump activity of SERCA2a in intact cells can be expressed by the Hill equation with an apparent affinity for Ca(2+) of 0.41 ± 0.0095 μm and a Hill coefficient of 5.7 ± 0.73. These results indicate that in the cellular environment the Ca(2+) dependence of ATPase activation is highly cooperative and that SERCA2a acts as a rapid switch to refill Ca(2+) stores in living cells for shaping the intracellular Ca(2+) dynamics. F-L577 will be useful for future studies on Ca(2+) signaling involving SERCA2a activity.
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Affiliation(s)
- Kanayo Satoh
- Laboratory for Developmental Neurobiology, Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
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10
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Leone FA, Furriel RPM, McNamara JC, Horisberger JD, Borin IA. Cation transport coupled to ATP hydrolysis by the (Na, K)-ATPase: An integrated, animated model. BIOCHEMISTRY AND MOLECULAR BIOLOGY EDUCATION : A BIMONTHLY PUBLICATION OF THE INTERNATIONAL UNION OF BIOCHEMISTRY AND MOLECULAR BIOLOGY 2010; 38:276-279. [PMID: 21567843 DOI: 10.1002/bmb.20404] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
An Adobe® animation is presented for use in undergraduate Biochemistry courses, illustrating the mechanism of Na(+) and K(+) translocation coupled to ATP hydrolysis by the (Na, K)-ATPase, a P(2c) -type ATPase, or ATP-powered ion pump that actively translocates cations across plasma membranes. The enzyme is also known as an E(1) /E(2) -ATPase as it undergoes conformational changes between the E(1) and E(2) forms during the pumping cycle, altering the affinity and accessibility of the transmembrane ion-binding sites. The animation is based on Horisberger's scheme that incorporates the most recent significant findings to have improved our understanding of the (Na, K)-ATPase structure-function relationship. The movements of the various domains within the (Na, K)-ATPase α-subunit illustrate the conformational changes that occur during Na(+) and K(+) translocation across the membrane and emphasize involvement of the actuator, nucleotide, and phosphorylation domains, that is, the "core engine" of the pump, with respect to ATP binding, cation transport, and ADP and P(i) release.
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Affiliation(s)
- Francisco A Leone
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, 14040-901 Ribeirão Preto, São Paulo, Brasil.
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11
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Janovská M, Kubala M, Šimánek V, Ulrichová J. Fluorescence of sanguinarine: spectral changes on interaction with amino acids. Phys Chem Chem Phys 2010; 12:11335-41. [DOI: 10.1039/b925828k] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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12
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Kubala M, Grycova L, Lansky Z, Sklenovsky P, Janovska M, Otyepka M, Teisinger J. Changes in electrostatic surface potential of Na+/K+-ATPase cytoplasmic headpiece induced by cytoplasmic ligand(s) binding. Biophys J 2009; 97:1756-64. [PMID: 19751681 DOI: 10.1016/j.bpj.2009.07.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2009] [Revised: 06/23/2009] [Accepted: 07/07/2009] [Indexed: 10/20/2022] Open
Abstract
A set of single-tryptophan mutants of the Na(+)/K(+)-ATPase isolated, large cytoplasmic loop connecting transmembrane helices M4 and M5 (C45) was prepared to monitor effects of the natural cytoplasmic ligands (i.e., Mg(2+) and/or ATP) binding. We introduced a novel method for the monitoring of the changes in the electrostatic surface potential (ESP) induced by ligand binding, using the quenching of the intrinsic tryptophan fluorescence by acrylamide or iodide. This approach opens a new way to understanding the interactions within the proteins. Our experiments revealed that the C45 conformation in the presence of the ATP (without magnesium) substantially differed from the conformation in the presence of Mg(2+) or MgATP or in the absence of any ligand not only in the sense of geometry but also in the sense of the ESP. Notably, the set of ESP-sensitive residues was different from the set of geometry-sensitive residues. Moreover, our data indicate that the effect of the ligand binding is not restricted only to the close environment of the binding site and that the information is in fact transmitted also to the distal parts of the molecule. This property could be important for the communication between the cytoplasmic headpiece and the cation binding sites located within the transmembrane domain.
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Affiliation(s)
- Martin Kubala
- Laboratory of Biophysics, Faculty of Science, Palacký University, Olomouc, Czech Republic.
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13
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Grycova L, Sklenovsky P, Lansky Z, Janovska M, Otyepka M, Amler E, Teisinger J, Kubala M. ATP and magnesium drive conformational changes of the Na+/K+-ATPase cytoplasmic headpiece. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:1081-91. [PMID: 19232513 DOI: 10.1016/j.bbamem.2009.02.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Revised: 01/16/2009] [Accepted: 02/03/2009] [Indexed: 10/21/2022]
Abstract
Conformational changes of the Na(+)/K(+)-ATPase isolated large cytoplasmic segment connecting transmembrane helices M4 and M5 (C45) induced by the interaction with enzyme ligands (i.e. Mg(2+) and/or ATP) were investigated by means of the intrinsic tryptophan fluorescence measurement and molecular dynamic simulations. Our data revealed that this model system consisting of only two domains retained the ability to adopt open or closed conformation, i.e. behavior, which is expected from the crystal structures of relative Ca(2+)-ATPase from sarco(endo)plasmic reticulum for the corresponding part of the entire enzyme. Our data revealed that the C45 is found in the closed conformation in the absence of any ligand, in the presence of Mg(2+) only, or in the simultaneous presence of Mg(2+) and ATP. Binding of the ATP alone (i.e. in the absence of Mg(2+)) induced open conformation of the C45. The fact that the transmembrane part of the enzyme was absent in our experiments suggested that the observed conformational changes are consequences only of the interaction with ATP or Mg(2+) and may not be related to the transported cations binding/release, as generally believed. Our data are consistent with the model, where ATP binding to the low-affinity site induces conformational change of the cytoplasmic part of the enzyme, traditionally attributed to E2-->E1 transition, and subsequent Mg(2+) binding to the enzyme-ATP complex induces in turn conformational change traditionally attributed to E1-->E2 transition.
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Affiliation(s)
- Lenka Grycova
- Institute of Physiology, Academy of Sciences of the Czech Republic, Vídenská 1083, 14220 Prague 4, Czech Republic
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14
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Masui DC, Silva ECC, Mantelatto FLM, McNamara JC, Barrabin H, Scofano HM, Fontes CFL, Furriel RPM, Leone FA. The crustacean gill (Na+,K+)-ATPase: allosteric modulation of high- and low-affinity ATP-binding sites by sodium and potassium. Arch Biochem Biophys 2008; 479:139-44. [PMID: 18796291 DOI: 10.1016/j.abb.2008.08.018] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2008] [Revised: 08/26/2008] [Accepted: 08/27/2008] [Indexed: 10/21/2022]
Abstract
The blue crab, Callinectes danae, tolerates exposure to a wide salinity range employing mechanisms of compensatory ion uptake when in dilute media. Although the gill (Na+,K+)-ATPase is vital to hyperosmoregulatory ability, the interactions occurring at the sites of ATP binding on the molecule itself are unknown. Here, we investigate the modulation by Na+ and K+ of homotropic interactions between the ATP-binding sites, and of phosphoenzyme formation of the (Na+,K+)-ATPase from the posterior gills of this euryhaline crab. The contribution of the high- and low-affinity ATP-binding sites to maximum velocity was similar for both Na+ and K+. However, in contrast to Na+, a threshold K+ concentration triggers the appearance of the high-affinity binding sites, displacing the saturation curve to lower ATP concentrations.Further, a low-affinity site for phosphorylation is present on the enzyme. These findings reveal notable differences in the catalytic mechanism of the crustacean (Na+,K+)-ATPase compared to the vertebrate enzyme.
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Affiliation(s)
- D C Masui
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Avenida Bandeirantes 3900, Ribeirão Preto 14040-901, SP, Brazil
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15
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Müller DJ, Wu N, Palczewski K. Vertebrate membrane proteins: structure, function, and insights from biophysical approaches. Pharmacol Rev 2008; 60:43-78. [PMID: 18321962 DOI: 10.1124/pr.107.07111] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Membrane proteins are key targets for pharmacological intervention because they are vital for cellular function. Here, we analyze recent progress made in the understanding of the structure and function of membrane proteins with a focus on rhodopsin and development of atomic force microscopy techniques to study biological membranes. Membrane proteins are compartmentalized to carry out extra- and intracellular processes. Biological membranes are densely populated with membrane proteins that occupy approximately 50% of their volume. In most cases membranes contain lipid rafts, protein patches, or paracrystalline formations that lack the higher-order symmetry that would allow them to be characterized by diffraction methods. Despite many technical difficulties, several crystal structures of membrane proteins that illustrate their internal structural organization have been determined. Moreover, high-resolution atomic force microscopy, near-field scanning optical microscopy, and other lower resolution techniques have been used to investigate these structures. Single-molecule force spectroscopy tracks interactions that stabilize membrane proteins and those that switch their functional state; this spectroscopy can be applied to locate a ligand-binding site. Recent development of this technique also reveals the energy landscape of a membrane protein, defining its folding, reaction pathways, and kinetics. Future development and application of novel approaches during the coming years should provide even greater insights to the understanding of biological membrane organization and function.
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Affiliation(s)
- Daniel J Müller
- Biotechnology Center, University of Technology, Dresden, Germany
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16
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Grycova L, Lansky Z, Friedlova E, Vlachova V, Kubala M, Obsilova V, Obsil T, Teisinger J. ATP binding site on the C-terminus of the vanilloid receptor. Arch Biochem Biophys 2007; 465:389-98. [PMID: 17706589 DOI: 10.1016/j.abb.2007.06.035] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2007] [Revised: 06/29/2007] [Accepted: 06/30/2007] [Indexed: 10/23/2022]
Abstract
Transient receptor potential channel vanilloid receptor subunit 1 (TRPV1) is a thermosensitive cation channel activated by noxious heat as well as a wide range of chemical stimuli. Although ATP by itself does not directly activate TRPV1, it was shown that intracellular ATP increases its activity by directly interacting with the Walker A motif residing on the C-terminus of TRPV1. In order to identify the amino acid residues that are essential for the binding of ATP to the TRPV1 channel, we performed the following point mutations of the Walker A motif: P732A, D733A, G734A, K735A, D736A, and D737A. Employing bulk fluorescence measurements, namely a TNP-ATP competition assay and FITC labelling and quenching experiments, we identified the key role of the K735 residue in the binding of the nucleotide. Experimental data was interpreted according to our molecular modelling simulations.
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Affiliation(s)
- Lenka Grycova
- Institute of Physiology, Academy of Sciences of the Czech Republic, Vídenská 1083, 14220 Prague, Czech Republic
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