1
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Monterroso B, Margolin W, Boersma AJ, Rivas G, Poolman B, Zorrilla S. Macromolecular Crowding, Phase Separation, and Homeostasis in the Orchestration of Bacterial Cellular Functions. Chem Rev 2024; 124:1899-1949. [PMID: 38331392 PMCID: PMC10906006 DOI: 10.1021/acs.chemrev.3c00622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 12/01/2023] [Accepted: 01/10/2024] [Indexed: 02/10/2024]
Abstract
Macromolecular crowding affects the activity of proteins and functional macromolecular complexes in all cells, including bacteria. Crowding, together with physicochemical parameters such as pH, ionic strength, and the energy status, influences the structure of the cytoplasm and thereby indirectly macromolecular function. Notably, crowding also promotes the formation of biomolecular condensates by phase separation, initially identified in eukaryotic cells but more recently discovered to play key functions in bacteria. Bacterial cells require a variety of mechanisms to maintain physicochemical homeostasis, in particular in environments with fluctuating conditions, and the formation of biomolecular condensates is emerging as one such mechanism. In this work, we connect physicochemical homeostasis and macromolecular crowding with the formation and function of biomolecular condensates in the bacterial cell and compare the supramolecular structures found in bacteria with those of eukaryotic cells. We focus on the effects of crowding and phase separation on the control of bacterial chromosome replication, segregation, and cell division, and we discuss the contribution of biomolecular condensates to bacterial cell fitness and adaptation to environmental stress.
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Affiliation(s)
- Begoña Monterroso
- Department
of Structural and Chemical Biology, Centro de Investigaciones Biológicas
Margarita Salas, Consejo Superior de Investigaciones
Científicas (CSIC), 28040 Madrid, Spain
| | - William Margolin
- Department
of Microbiology and Molecular Genetics, McGovern Medical School, UTHealth-Houston, Houston, Texas 77030, United States
| | - Arnold J. Boersma
- Cellular
Protein Chemistry, Bijvoet Centre for Biomolecular Research, Faculty
of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Germán Rivas
- Department
of Structural and Chemical Biology, Centro de Investigaciones Biológicas
Margarita Salas, Consejo Superior de Investigaciones
Científicas (CSIC), 28040 Madrid, Spain
| | - Bert Poolman
- Department
of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Silvia Zorrilla
- Department
of Structural and Chemical Biology, Centro de Investigaciones Biológicas
Margarita Salas, Consejo Superior de Investigaciones
Científicas (CSIC), 28040 Madrid, Spain
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2
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Gadzuk-Shea MM, Hubbard EE, Gozzo TA, Bush MF. Sample pH Can Drift during Native Mass Spectrometry Experiments: Results from Ratiometric Fluorescence Imaging. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023; 34:1675-1684. [PMID: 37405934 PMCID: PMC10563179 DOI: 10.1021/jasms.3c00147] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/07/2023]
Abstract
The ability of nanoelectrospray ionization (nanoESI) to generate a continuous flow of charged droplets relies on the electrolytic nature of the process. This electrochemistry can lead to the accumulation of redox products in the sample solution. This consequence can have significant implications for native mass spectrometry (MS), which aims to probe the structures and interactions of biomolecules in solution. Here, ratiometric fluorescence imaging and a pH-sensitive, fluorescent probe are used to quantify changes in solution pH during nanoESI under conditions relevant to native MS. Results show that the extent and rate of change in sample pH depends on several experimental parameters. There is a strong correlation between the extent and rate of change in solution pH and the magnitude of both the nanoESI current and electrolyte concentration. Smaller changes in solution pH are observed during experiments when a negative potential is applied than for those when a positive potential is applied. Finally, we make specific recommendations for designing native MS experiments that control for these effects.
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Affiliation(s)
- Meagan M. Gadzuk-Shea
- University of Washington, Department of Chemistry, Box 351700, Seattle, WA 98195-1700
- Current Affiliation: Discovery Biology, Discovery Sciences, Biopharmaceuticals R&D, AstraZeneca, Waltham, MA 02451
| | - Evan E. Hubbard
- University of Washington, Department of Chemistry, Box 351700, Seattle, WA 98195-1700
- Current Affiliation: Current Affiliation: Department of Chemistry, University of California, Riverside, California 92521
| | - Theresa A. Gozzo
- University of Washington, Department of Chemistry, Box 351700, Seattle, WA 98195-1700
| | - Matthew F Bush
- University of Washington, Department of Chemistry, Box 351700, Seattle, WA 98195-1700
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3
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Rioux KL, Delaney S. Ionic strength modulates excision of uracil by SMUG1 from nucleosome core particles. DNA Repair (Amst) 2023; 125:103482. [PMID: 36931160 PMCID: PMC10073303 DOI: 10.1016/j.dnarep.2023.103482] [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: 12/20/2022] [Revised: 03/04/2023] [Accepted: 03/07/2023] [Indexed: 03/14/2023]
Abstract
Ionic strength affects many cellular processes including the packaging of genetic material in eukaryotes. For example, chromatin fibers are compacted in high ionic strength environments as are the minimal unit of packaging in chromatin, nucleosome core particles (NCPs). Furthermore, ionic strength is known to modulate several aspects of NCP dynamics including transient unwrapping of DNA from the histone protein core, nucleosome gaping, and intra- and internucleosomal interactions of the N-terminal histone tails. Changes in NCP structure may also impact interactions of transcriptional, repair, and other cellular machinery with nucleosomal DNA. One repair process, base excision repair (BER), is impacted by NCP structure and may be further influenced by changes in ionic strength. Here we examine the effects of ionic strength on the initiation of BER using biochemical assays. Using a population of NCPs containing uracil (U) at dozens of geometric locations, excision of U by single-strand selective monofunctional uracil DNA glycosylase (SMUG1) is assessed at higher and lower ionic strengths. SMUG1 has increased excision activity in the lower ionic strength conditions. On duplex DNA, however, SMUG1 activity is largely unaffected by ionic strength except at short incubation times, suggesting that changes in SMUG1 activity are likely due to alterations in NCP structure and dynamics. These results allow us to further understand the cellular role of SMUG1 in a changing ionic environment and broadly contribute to the understanding of BER on chromatin and genomic stability.
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Affiliation(s)
- Katelyn L Rioux
- Department of Chemistry, Brown University, Providence, RI, USA
| | - Sarah Delaney
- Department of Chemistry, Brown University, Providence, RI, USA.
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4
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McDonald AG, Tipton KF. Parameter Reliability and Understanding Enzyme Function. Molecules 2022; 27:263. [PMID: 35011495 PMCID: PMC8746786 DOI: 10.3390/molecules27010263] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Revised: 12/21/2021] [Accepted: 12/24/2021] [Indexed: 11/16/2022] Open
Abstract
Knowledge of the Michaelis-Menten parameters and their meaning in different circumstances is an essential prerequisite to understanding enzyme function and behaviour. The published literature contains an abundance of values reported for many enzymes. The problem concerns assessing the appropriateness and validity of such material for the purpose to which it is to be applied. This review considers the evaluation of such data with particular emphasis on the assessment of its fitness for purpose.
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Affiliation(s)
- Andrew G. McDonald
- School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, D02 PN40 Dublin, Ireland;
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5
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Arabiyat AS, Chen H, Erndt-Marino J, Burkhard K, Scola L, Fleck A, Wan LQ, Hahn MS. Hyperosmolar Ionic Solutions Modulate Inflammatory Phenotype and sGAG Loss in a Cartilage Explant Model. Cartilage 2021; 13:713S-721S. [PMID: 32975437 PMCID: PMC8804856 DOI: 10.1177/1947603520961167] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
OBJECTIVE The objective of this study was to compare the effects of hyperosmolar sodium (Na+), lithium (Li+) and potassium (K+) on catabolic and inflammatory osteoarthritis (OA) markers and sulfated glycosaminoglycan (sGAG) loss in TNF-α-stimulated cartilage explants. METHODS Explants from bovine stifle joints were stimulated with TNF-α for 1 day to induce cartilage degradation followed by supplementation with 50 mM potassium chloride (KCl), 50 mM lithium chloride (LiCl), 50 mM sodium chloride (NaCl), or 100 nM dexamethasone for an additional 6 days. We assessed the effect of TNF-α stimulation and hyperosmolar ionic treatment on sGAG loss and expression of OA-associated proteins: ADAMTS-5, COX-2, MMP-1, MMP-13, and VEGF. RESULTS TNF-α treatment increased sGAG loss (P < 0.001) and expression of COX-2 (P = 0.018), MMP-13 (P < 0.001), and VEGF (P = 0.017) relative to unstimulated controls. Relative to activated controls, LiCl and dexamethasone treatment attenuated sGAG loss (P = 0.008 and P = 0.042, respectively) and expression of MMP-13 (P = 0.005 and P = 0.036, respectively). In contrast, KCl treatment exacerbated sGAG loss (P = 0.032) and MMP-1 protein expression (P = 0.010). NaCl treatment, however, did not alter sGAG loss or expression of OA-related proteins. Comparing LiCl and KCl treatment shows a potent reduction (P < 0.05) in catabolic and inflammatory mediators following LiCl treatment. CONCLUSION These results suggest that these ionic species elicit varying responses in TNF-α-stimulated explants. Cumulatively, these findings support additional studies of hyperosmolar ionic solutions for potential development of novel intraarticular injections targeting OA.
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Affiliation(s)
- Ahmad S. Arabiyat
- Department of Biomedical Engineering,
Rensselaer Polytechnic Institute (RPI), Troy, NY, USA
- Center for Biotechnology and
Interdisciplinary Studies, Rensselaer Polytechnic Institute (RPI), Troy, NY,
USA
| | - Hongyu Chen
- Department of Biomedical Engineering,
Rensselaer Polytechnic Institute (RPI), Troy, NY, USA
- Center for Biotechnology and
Interdisciplinary Studies, Rensselaer Polytechnic Institute (RPI), Troy, NY,
USA
| | - Josh Erndt-Marino
- Department of Biomedical Engineering,
Tufts University, Medford, MA, USA
| | - Katie Burkhard
- Department of Biomedical Engineering,
Rensselaer Polytechnic Institute (RPI), Troy, NY, USA
| | - Lisa Scola
- Department of Biomedical Engineering,
Rensselaer Polytechnic Institute (RPI), Troy, NY, USA
| | - Allison Fleck
- Department of Biomedical Engineering,
Rensselaer Polytechnic Institute (RPI), Troy, NY, USA
- Center for Biotechnology and
Interdisciplinary Studies, Rensselaer Polytechnic Institute (RPI), Troy, NY,
USA
| | - Leo Q. Wan
- Department of Biomedical Engineering,
Rensselaer Polytechnic Institute (RPI), Troy, NY, USA
- Center for Biotechnology and
Interdisciplinary Studies, Rensselaer Polytechnic Institute (RPI), Troy, NY,
USA
| | - Mariah S. Hahn
- Department of Biomedical Engineering,
Rensselaer Polytechnic Institute (RPI), Troy, NY, USA
- Center for Biotechnology and
Interdisciplinary Studies, Rensselaer Polytechnic Institute (RPI), Troy, NY,
USA
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6
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Aplin CP, Miller RC, Kay TM, Heikal AA, Boersma AJ, Sheets ED. Fluorescence depolarization dynamics of ionic strength sensors using time-resolved anisotropy. Biophys J 2021; 120:1417-1430. [PMID: 33582140 DOI: 10.1016/j.bpj.2021.01.035] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 12/17/2020] [Accepted: 01/20/2021] [Indexed: 10/22/2022] Open
Abstract
Eukaryotic cells exploit dynamic and compartmentalized ionic strength to impact a myriad of biological functions such as enzyme activities, protein-protein interactions, and catalytic functions. Herein, we investigated the fluorescence depolarization dynamics of recently developed ionic strength biosensors (mCerulean3-linker-mCitrine) in Hofmeister salt (KCl, NaCl, NaI, and Na2SO4) solutions. The mCerulean3-mCitrine acts as a Förster resonance energy transfer (FRET) pair, tethered together by two oppositely charged α-helices in the linker region. We developed a time-resolved fluorescence depolarization anisotropy approach for FRET analyses, in which the donor (mCerulean3) is excited by 425-nm laser pulses, followed by fluorescence depolarization analysis of the acceptor (mCitrine) in KE (lysine-glutamate), arginine-aspartate, and arginine-glutamate ionic strength sensors with variable amino acid sequences. Similar experiments were carried out on the cleaved sensors as well as an E6G2 construct, which has neutral α-helices in the linker region, as a control. Our results show distinct dynamics of the intact and cleaved sensors. Importantly, the FRET efficiency decreases and the donor-acceptor distance increases as the environmental ionic strength increases. Our chemical equilibrium analyses of the collapsed-to-stretched conformational state transition of KE reveal that the corresponding equilibrium constant and standard Gibbs free energy changes are ionic strength dependent. We also tested the existing theoretical models for FRET analyses using steady-state anisotropy, which reveal that the angle between the dipole moments of the donor and acceptor in the KE sensor are sensitive to the ionic strength. These results help establish the time-resolved depolarization dynamics of these genetically encoded donor-acceptor pairs as a quantitative means for FRET analysis, which complement traditional methods such as time-resolved fluorescence for future in vivo studies.
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Affiliation(s)
- Cody P Aplin
- Department of Chemistry and Biochemistry, University of Minnesota Duluth, Duluth, Minnesota
| | - Robert C Miller
- Department of Chemistry and Biochemistry, University of Minnesota Duluth, Duluth, Minnesota
| | - Taryn M Kay
- Department of Physics and Astronomy, University of Minnesota Duluth, Duluth, Minnesota
| | - Ahmed A Heikal
- Department of Chemistry and Biochemistry, University of Minnesota Duluth, Duluth, Minnesota.
| | - Arnold J Boersma
- DWI-Leibniz Institute for Interactive Materials, Aachen, Germany.
| | - Erin D Sheets
- Department of Chemistry and Biochemistry, University of Minnesota Duluth, Duluth, Minnesota.
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7
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Faraj SE, Valsecchi WM, Cerf NT, Fedosova NU, Rossi RC, Montes MR. The interaction of Na +, K +, and phosphate with the gastric H,K-ATPase. Kinetics of E1-E2 conformational changes assessed by eosin fluorescence measurements. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1863:183477. [PMID: 32949561 DOI: 10.1016/j.bbamem.2020.183477] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 09/10/2020] [Accepted: 09/11/2020] [Indexed: 12/12/2022]
Abstract
H,K-ATPase and Na,K-ATPase show the highest degree of sequence similarity among all other members of the P-type ATPases family. To explore their common features in terms of ligand binding, we evaluated conformational transitions due to the binding of Na+, K+ and Pi in the H,K-ATPase, and compared the results with those obtained for the Na,K-ATPase. This work shows that eosin fluorescence time courses provide a reasonably precise method to study the kinetics of the E1-E2 conformational changes in the H,K-ATPase. We found that, although Na+ shifts the equilibrium toward the E1 conformation and seems to compete with H+ in ATPase activity assays, it was neither possible to isolate a Na+-occluded state, nor to reveal an influx of Na+ related to H,K-ATPase activity. The high rate of the E2K → E1 transition found for the H,K-ATPase, which is not compatible with the presence of a K+-occluded form, agrees with the negligible level of occluded Rb+ (used as a K+ congener) found in the absence of added ligands. The use of vanadate and fluorinated metals to induce E2P-like states increased the level of occluded Rb+ and suggests that-during dephosphorylation-the probability of K+ to remain occluded increases from the E2P-ground to the E2P-product state. From kinetic experiments we found an unexpected increase in the values of kobs for E2P formation with [Pi]; consequently, to obey the Albers-Post model, the binding of Pi to the E2 state cannot be a rapid-equilibrium reaction.
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Affiliation(s)
- S E Faraj
- Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Departamento de Química Biológica, Buenos Aires, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) - Universidad de Buenos Aires, Instituto de Química y Fisicoquímica Biológicas "Prof. Alejandro C. Paladini" (IQUIFIB), Buenos Aires, Argentina
| | - W M Valsecchi
- Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Departamento de Química Biológica, Buenos Aires, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) - Universidad de Buenos Aires, Instituto de Química y Fisicoquímica Biológicas "Prof. Alejandro C. Paladini" (IQUIFIB), Buenos Aires, Argentina
| | - N T Cerf
- Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Departamento de Química Biológica, Buenos Aires, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) - Universidad de Buenos Aires, Instituto de Química y Fisicoquímica Biológicas "Prof. Alejandro C. Paladini" (IQUIFIB), Buenos Aires, Argentina
| | - N U Fedosova
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - R C Rossi
- Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Departamento de Química Biológica, Buenos Aires, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) - Universidad de Buenos Aires, Instituto de Química y Fisicoquímica Biológicas "Prof. Alejandro C. Paladini" (IQUIFIB), Buenos Aires, Argentina
| | - M R Montes
- Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Departamento de Química Biológica, Buenos Aires, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) - Universidad de Buenos Aires, Instituto de Química y Fisicoquímica Biológicas "Prof. Alejandro C. Paladini" (IQUIFIB), Buenos Aires, Argentina.
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8
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Spice AJ, Aw R, Bracewell DG, Polizzi KM. Improving the reaction mix of a Pichia pastoris cell-free system using a design of experiments approach to minimise experimental effort. Synth Syst Biotechnol 2020; 5:137-144. [PMID: 32637667 PMCID: PMC7320237 DOI: 10.1016/j.synbio.2020.06.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 06/07/2020] [Accepted: 06/08/2020] [Indexed: 12/20/2022] Open
Abstract
A renaissance in cell-free protein synthesis (CFPS) is underway, enabled by the acceleration and adoption of synthetic biology methods. CFPS has emerged as a powerful platform technology for synthetic gene network design, biosensing and on-demand biomanufacturing. Whilst primarily of bacterial origin, cell-free extracts derived from a variety of host organisms have been explored, aiming to capitalise on cellular diversity and the advantageous properties associated with those organisms. However, cell-free extracts produced from eukaryotes are often overlooked due to their relatively low yields, despite the potential for improved protein folding and posttranslational modifications. Here we describe further development of a Pichia pastoris cell-free platform, a widely used expression host in both academia and the biopharmaceutical industry. Using a minimised Design of Experiments (DOE) approach, we were able to increase the productivity of the system by improving the composition of the complex reaction mixture. This was achieved in a minimal number of experimental runs, within the constraints of the design and without the need for liquid-handling robots. In doing so, we were able to estimate the main effects impacting productivity in the system and increased the protein synthesis of firefly luciferase and the biopharmaceutical HSA by 4.8-fold and 3.5-fold, respectively. This study highlights the P. pastoris-based cell-free system as a highly productive eukaryotic platform and displays the value of minimised DOE designs.
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Key Words
- AB, Albumin Blue
- CFPS, cell-free protein synthesis
- CHO, Chinese hamster ovary cells
- Cell-free protein synthesis
- DOE, design of Experiments
- DSD, definitive screening design
- Design of experiments (DOE)
- HSA, human serum albumin
- IRES, internal ribosome entry site
- Pichia pastoris
- RRL, rabbit reticulocyte lysate
- Synthetic biology
- VLP, virus-like particles
- WGE, wheat-germ etract
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Affiliation(s)
- Alex J. Spice
- Department of Chemical Engineering, Imperial College London, London, UK
- Imperial College Centre for Synthetic Biology, Imperial College London, UK
| | - Rochelle Aw
- Department of Chemical Engineering, Imperial College London, London, UK
- Imperial College Centre for Synthetic Biology, Imperial College London, UK
| | - Daniel G. Bracewell
- Department of Biochemical Engineering, University College London, London, UK
| | - Karen M. Polizzi
- Department of Chemical Engineering, Imperial College London, London, UK
- Imperial College Centre for Synthetic Biology, Imperial College London, UK
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9
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Miller RC, Aplin CP, Kay TM, Leighton R, Libal C, Simonet R, Cembran A, Heikal AA, Boersma AJ, Sheets ED. FRET Analysis of Ionic Strength Sensors in the Hofmeister Series of Salt Solutions Using Fluorescence Lifetime Measurements. J Phys Chem B 2020; 124:3447-3458. [PMID: 32267692 DOI: 10.1021/acs.jpcb.9b10498] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Living cells are complex, crowded, and dynamic and continually respond to environmental and intracellular stimuli. They also have heterogeneous ionic strength with compartmentalized variations in both intracellular concentrations and types of ions. These challenges would benefit from the development of quantitative, noninvasive approaches for mapping the heterogeneous ionic strength fluctuations in living cells. Here, we investigated a class of recently developed ionic strength sensors that consists of mCerulean3 (a cyan fluorescent protein) and mCitrine (a yellow fluorescent protein) tethered via a linker made of two charged α-helices and a flexible loop. The two helices are designed to bear opposite charges, which is hypothesized to increase the ionic screening and therefore a larger intermolecular distance. In these protein constructs, mCerulean3 and mCitrine act as a donor-acceptor pair undergoing Förster resonance energy transfer (FRET) that is dependent on both the linker amino acids and the environmental ionic strength. Using time-resolved fluorescence of the donor (mCerulean3), we determined the sensitivity of the energy transfer efficiencies and the donor-acceptor distances of these sensors at variable concentrations of the Hofmeister series of salts (KCl, LiCl, NaCl, NaBr, NaI, Na2SO4). As controls, similar measurements were carried out on the FRET-incapable, enzymatically cleaved counterparts of these sensors as well as a construct designed with two electrostatically neutral α-helices (E6G2). Our results show that the energy transfer efficiencies of these sensors are sensitive to both the linker amino acid sequence and the environmental ionic strength, whereas the sensitivity of these sensors to the identity of the dissolved ions of the Hofmeister series of salts seems limited. We also developed a theoretical framework to explain the observed trends as a function of the ionic strength in terms of the Debye screening of the electrostatic interaction between the two charged α-helices in the linker region. These controlled solution studies represent an important step toward the development of rationally designed FRET-based environmental sensors while offering different models for calculating the energy transfer efficiency using time-resolved fluorescence that is compatible with future in vivo studies.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Arnold J Boersma
- DWI-Leibniz Institute for Interactive Materials, Forckenbeckstraße 50, 52056 Aachen, Germany
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10
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Matyszewska D, Zatloukalova M, Bilewicz R. Activity of Na+/K+-ATPase in model lipid membrane at air-water interface. Electrochim Acta 2019. [DOI: 10.1016/j.electacta.2019.03.063] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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11
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Khan MA. Phosphorylation of translation initiation factor eIFiso4E promotes translation through enhanced binding to potyvirus VPg. J Biochem 2019; 165:167-176. [PMID: 30371907 DOI: 10.1093/jb/mvy091] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Accepted: 10/28/2018] [Indexed: 12/13/2022] Open
Abstract
Interactions of phosphorylated eIFiso4E binding to VPg as a function of temperature and ionic strength were assessed employing fluorescence spectroscopic. Phosphorylation increased the binding affinity ∼3.5-fold between VPg and eIFiso4E under equilibrium conditions. Binding affinity of VPg for eIFiso4Ep correlates with the ability to enhance in vitro protein synthesis. Addition of VPg and eIFiso4Ep together to Dep WGE enhances the translation for both uncapped and capped mRNA. However, capped mRNA translation was inhibited with addition of eIFiso4Ep alone in dep WGE, suggesting that phosphorylation prevents the cap binding and favours the VPg binding to promotes translation. Temperature dependence showed that the phosphorylated form of the eIFiso4E is preferred for complex formation. A van't Hoff analysis reveals that eIFiso4Ep binding to VPg was enthalpy driven (ΔH = -43.9 ± 0.3 kJ.mol-1) and entropy-opposed (ΔS = -4.3 ± 0.1 J.mol-1K-1). Phosphorylation increased the enthalpic contributions ∼33% for eIFiso4Ep-VPg complex. The thermodynamic values and ionic strength dependence of binding data suggesting that phosphorylation increased hydrogen-bonding and decreased hydrophobic interactions, which leads to more stable complex formation and favour efficient viral translation. Overall these data correlate well with the observed translational data and provide more detailed information on the translational strategy of potyviruses.
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Affiliation(s)
- Mateen A Khan
- Department of Chemistry & Biochemistry, Hunter College of the City University of New York, 695 Park Ave, New York, USA.,Department of Life Sciences, College of Science and General Studies, Alfaisal University, Takhasusi Street, P.O. Box-50927, Riyadh, Saudi Arabia
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12
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Dopp BJL, Tamiev DD, Reuel NF. Cell-free supplement mixtures: Elucidating the history and biochemical utility of additives used to support in vitro protein synthesis in E. coli extract. Biotechnol Adv 2019; 37:246-258. [DOI: 10.1016/j.biotechadv.2018.12.006] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Revised: 12/06/2018] [Accepted: 12/15/2018] [Indexed: 12/18/2022]
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13
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Abstract
![]()
Knowledge of the
ionic strength in cells is required to understand
the in vivo biochemistry of the charged biomacromolecules.
Here, we present the first sensors to determine the ionic strength
in living cells, by designing protein probes based on Förster
resonance energy transfer (FRET). These probes allow observation of
spatiotemporal changes in the ionic strength on the single-cell level.
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Affiliation(s)
- Boqun Liu
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Bert Poolman
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Arnold J. Boersma
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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14
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Suchaoin W, Pereira de Sousa I, Netsomboon K, Lam HT, Laffleur F, Bernkop-Schnürch A. Development and in vitro evaluation of zeta potential changing self-emulsifying drug delivery systems for enhanced mucus permeation. Int J Pharm 2016; 510:255-62. [DOI: 10.1016/j.ijpharm.2016.06.045] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Revised: 06/03/2016] [Accepted: 06/17/2016] [Indexed: 12/31/2022]
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15
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SILVA JUNIOR IZANM, CASTRO MARIACLÍCIAS, SILVA DILSON, CORTEZ CÉLIAM. Relevance of Hydrodynamic Effects for the Calculation of Outer Surface Potential of Biological Membrane Using Electrophoretic Data. ACTA ACUST UNITED AC 2016; 88:751-63. [DOI: 10.1590/0001-3765201620140530] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 08/31/2015] [Indexed: 11/21/2022]
Abstract
ABSTRACT In this paper, we present the results of a study on the influence of hydrodynamic effects on the surface potentials of the erythrocyte membrane, comparing two different models formulated to simulate the electrophoretic movement of a biological cell: the classical Helmholtz-Smoluchowski model and a model presented by Hsu et al. (1996). This model considers hydrodynamic effects to describe the distribution of the fluid velocity. The electric potential equation was obtained from the non-linear Poisson-Boltzmann equation, considering the spatial distribution of electrical charges fixed in glycocalyx and cytoplasmic proteins, as well as electrolyte charges and ones fixed on the surfaces of lipidic bilayer. Our results show that the Helmholtz-Smoluchowski model is not able to reflect the real forces responsible to the electrophoretic behavior of cell, because it does not take account the hydrodynamic effects of glycocalyx. This charged network that covers cellular surface constitutes a complex physical system whose electromechanical characteristics cannot be neglected. Then, supporting the hypothesis of other authors, we suggest that, in electrophoretic motion analyses of cells, the classical model represents a limiting case of models that take into account hydrodynamic effects to describe the velocity distribution of fluid.
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Affiliation(s)
| | | | - DILSON SILVA
- Universidade do Estado do Rio de Janeiro, Brazil
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16
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Dzikovski B, Livshits V, Freed J. Interaction of Spin-Labeled Lipid Membranes with Transition Metal Ions. J Phys Chem B 2015; 119:13330-46. [PMID: 26490692 PMCID: PMC4762260 DOI: 10.1021/acs.jpcb.5b08165] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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The large values of spin relaxation
enhancement (RE) for PC spin-labels
in the phospholipid membrane induced by paramagnetic metal salts dissolved
in the aqueous phase can be explained by Heisenberg spin exchange
due to conformational fluctuations of the nitroxide group as a result
of membrane fluidity, flexibility of lipid chains, and, possibly,
amphiphilic nature of the nitroxide label. Whether the magnetic interaction
occurs predominantly via Heisenberg spin exchange (Ni) or by the dipole–dipole
(Gd) mechanism, it is essential for the paramagnetic ion to get into
close proximity to the nitroxide moiety for efficient RE. For different
salts of Ni the RE in phosphatidylcholine membranes follows the anionic
Hofmeister series and reflects anion adsorption followed by anion-driven
attraction of paramagnetic cations on the choline groups. This adsorption
is higher for chaotropic ions, e.g., perchlorate. (A chaotropic agent
is a molecule in water solution that can disrupt the hydrogen bonding
network between water molecules.) However, there is no anionic dependence
of RE for model membranes made from negatively charged lipids devoid
of choline groups. We used Ni-induced RE to study the thermodynamics
and electrostatics of ion/membrane interactions. We also studied the
effect of membrane composition and the phase state on the RE values.
In membranes with cholesterol a significant difference is observed
between PC labels with nitroxide tethers long enough vs not long enough
to reach deep into the membrane hydrophobic core behind the area of
fused cholesterol rings. This study indicates one must be cautious
in interpreting data obtained by PC labels in fluid membranes in terms
of probing membrane properties at different immersion depths when
it can be affected by paramagnetic species at the membrane surface.
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Affiliation(s)
- Boris Dzikovski
- National Biomedical Center for Advanced ESR Technology (ACERT), Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University , Ithaca, New York 14853, United States.,Centre of Photochemistry, Russian Academy of Sciences , ul. Novatorov 7a, 117427 Moscow, Russia
| | - Vsevolod Livshits
- Centre of Photochemistry, Russian Academy of Sciences , ul. Novatorov 7a, 117427 Moscow, Russia
| | - Jack Freed
- National Biomedical Center for Advanced ESR Technology (ACERT), Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University , Ithaca, New York 14853, United States
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17
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Tadini-Buoninsegni F, Moncelli MR, Peruzzi N, Ninham BW, Dei L, Nostro PL. Hofmeister effect of anions on calcium translocation by sarcoplasmic reticulum Ca(2+)-ATPase. Sci Rep 2015; 5:14282. [PMID: 26435197 PMCID: PMC4593048 DOI: 10.1038/srep14282] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Accepted: 07/24/2015] [Indexed: 11/18/2022] Open
Abstract
The occurrence of Hofmeister (specific ion) effects in various membrane-related physiological processes is well documented. For example the effect of anions on the transport activity of the ion pump Na+, K+-ATPase has been investigated. Here we report on specific anion effects on the ATP-dependent Ca2+ translocation by the sarcoplasmic reticulum Ca2+-ATPase (SERCA). Current measurements following ATP concentration jumps on SERCA-containing vesicles adsorbed on solid supported membranes were carried out in the presence of different potassium salts. We found that monovalent anions strongly interfere with ATP-induced Ca2+ translocation by SERCA, according to their increasing chaotropicity in the Hofmeister series. On the contrary, a significant increase in Ca2+ translocation was observed in the presence of sulphate. We suggest that the anions can affect the conformational transition between the phosphorylated intermediates E1P and E2P of the SERCA cycle. In particular, the stabilization of the E1P conformation by chaotropic anions seems to be related to their adsorption at the enzyme/water and/or at the membrane/water interface, while the more kosmotropic species affect SERCA conformation and functionality by modifying the hydration layers of the enzyme.
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Affiliation(s)
| | - Maria Rosa Moncelli
- Department of Chemistry "Ugo Schiff", University of Florence, 50019 Sesto Fiorentino (Firenze), Italy
| | - Niccolò Peruzzi
- Department of Chemistry "Ugo Schiff", University of Florence, 50019 Sesto Fiorentino (Firenze), Italy.,CSGI, University of Florence, 50019 Sesto Fiorentino (Firenze), Italy
| | - Barry W Ninham
- Research School of Physical Sciences and Engineering, Australian National University, Canberra, Australia 0200
| | - Luigi Dei
- Department of Chemistry "Ugo Schiff", University of Florence, 50019 Sesto Fiorentino (Firenze), Italy.,CSGI, University of Florence, 50019 Sesto Fiorentino (Firenze), Italy
| | - Pierandrea Lo Nostro
- Department of Chemistry "Ugo Schiff", University of Florence, 50019 Sesto Fiorentino (Firenze), Italy.,CSGI, University of Florence, 50019 Sesto Fiorentino (Firenze), Italy
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18
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Gavriilidou AFM, Gülbakan B, Zenobi R. Influence of Ammonium Acetate Concentration on Receptor–Ligand Binding Affinities Measured by Native Nano ESI-MS: A Systematic Study. Anal Chem 2015; 87:10378-84. [DOI: 10.1021/acs.analchem.5b02478] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Agni F. M. Gavriilidou
- ETH Zurich, Department of Chemistry and Applied
Biosciences, CH-8093 Zurich, Switzerland
| | - Basri Gülbakan
- Institute
of Child Health, Division of Pediatric Basic Sciences, Hacettepe University, 06100 Ankara, Turkey
| | - Renato Zenobi
- ETH Zurich, Department of Chemistry and Applied
Biosciences, CH-8093 Zurich, Switzerland
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19
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Bonaiuto E, Grancara S, Martinis P, Stringaro A, Colone M, Agostinelli E, Macone A, Stevanato R, Vianello F, Toninello A, Di Paolo ML. A novel enzyme with spermine oxidase properties in bovine liver mitochondria: identification and kinetic characterization. Free Radic Biol Med 2015; 81:88-99. [PMID: 25591967 DOI: 10.1016/j.freeradbiomed.2015.01.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Revised: 12/19/2014] [Accepted: 01/04/2015] [Indexed: 01/31/2023]
Abstract
The uptake of spermine into mammalian mitochondria indicated the need to identify its catabolic pathway in these organelles. Bovine liver mitochondria were therefore purified and their capacity for natural polyamine uptake was verified. A kinetic approach was then used to determine the presence of an MDL 72527-sensitive enzyme with spermine oxidase activity in the matrix of bovine liver mitochondria. Western blot analysis of mitochondrial fractions and immunogold electron microscopy observations of purified mitochondria unequivocally confirmed the presence of a protein recognized by anti-spermine oxidase antibodies in the mitochondrial matrix. Preliminary kinetic characterization showed that spermine is the preferred substrate of this enzyme; lower activity was detected with spermidine and acetylated polyamines. Catalytic efficiency comparable to that of spermine was also found for 1-aminododecane. The considerable effect of ionic strength on the Vmax/KM ratio suggested the presence of more than one negatively charged zone inside the active site cavity of this mitochondrial enzyme, which is probably involved in the docking of positively charged substrates. These findings indicate that the bovine liver mitochondrial matrix contains an enzyme belonging to the spermine oxidase class. Because H2O2 is generated by spermine oxidase activity, the possible involvement of the latter as an important signaling transducer under both physiological and pathological conditions should be considered.
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Affiliation(s)
- Emanuela Bonaiuto
- Department of Molecular Medicine, University of Padova, Via G. Colombo 3, 35131 Padova, Italy
| | - Silvia Grancara
- Department of Biomedical Sciences, University of Padova, Via G. Colombo 3, 35131 Padova, Italy
| | - Pamela Martinis
- Department of Biomedical Sciences, University of Padova, Via G. Colombo 3, 35131 Padova, Italy
| | - Annarita Stringaro
- Department of Technology and Health, Italian Institute of Health, 00161 Roma, Italy
| | - Marisa Colone
- Department of Technology and Health, Italian Institute of Health, 00161 Roma, Italy
| | - Enzo Agostinelli
- Istituto Pasteur-Fondazione Cenci Bolognetti, Department of Biochemical Sciences "A. Rossi Fanelli," Sapienza University of Rome and Institute of Biology and Molecular Pathology, Italian Research Council, P.le Aldo Moro 5, 00185 Roma, Italy
| | - Alberto Macone
- Istituto Pasteur-Fondazione Cenci Bolognetti, Department of Biochemical Sciences "A. Rossi Fanelli," Sapienza University of Rome and Institute of Biology and Molecular Pathology, Italian Research Council, P.le Aldo Moro 5, 00185 Roma, Italy
| | - Roberto Stevanato
- Department of Molecular Science and Nanosystems, Università Ca' Foscari, Dorsoduro 2137, 30123 Venezia, Italy
| | - Fabio Vianello
- Department of Comparative Biomedicine and Food Science, Polo Agripolis, Viale dell'Università 16, University of Padova, 35020 Legnaro, Italy; Regional Centre for Advanced Technologies and Materials, Department of Physical Chemistry, Palacky University in Olomouc, 17 Listopadu 1192/12, 771 46 Olomouc, Czech Republic
| | - Antonio Toninello
- Department of Biomedical Sciences, University of Padova, Via G. Colombo 3, 35131 Padova, Italy.
| | - Maria Luisa Di Paolo
- Department of Molecular Medicine, University of Padova, Via G. Colombo 3, 35131 Padova, Italy; Consorzio Interuniversitario "Istituto Nazionale Biostrutture e Biosistemi," Viale delle medaglie d'Oro 305, 00136 Roma, Italy.
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20
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GENET S, COSTALAT R. THE ROLE OF MEMBRANE ELECTROSTATICS IN THE REGULATION OF CELL VOLUME AND ION CONCENTRATIONS. J BIOL SYST 2011. [DOI: 10.1142/s0218339099000188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
We present a model to study how membrane surface negative charges can affect the electro-osmotic regulation properties of a cell. This model is based on the cellular analog proposed by Jakobsson, which includes passive and active ion transports; we further introduce the effect of membrane surface charges, using a generalized formulation of the Gouy–Chapman theory. We derive a system of nonlinear differential-algebraic equations (DAEs) which describes the dynamics of the cellular analog. The system admits a unique asymptotically stable stationary state, in which the Na-pump rate, which is crucial for electro-osmotic regulation, is inversely related to the Ca2+level in the extracellular milieu; numerical integration shows that this apparent inhibition of the Na-pump by external Ca2+results from a decrease in the electrostatic field produced by surface charges at the external side of the membrane. Furthermore, the degree of stability of the stationary state dramatically depends on the amount of negative charges on the membrane; a maximal stability is obtained for densities around - e /500 Å2, where the Na-pump is maximally activated by an increase in the Na content of the cytoplasm.
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Affiliation(s)
- S. GENET
- Service d'Imagerie Cellulaire, UPRESA 8080, Développement et Evolution, Bâtiment 440, Université Paris-Sud, 91405 Orsay Cedex, France
| | - R. COSTALAT
- CREARE, INSERM U. 483, Université Pierre et Marie Curie, Boîte 23, 9 quai Saint-Bernard, 75252 Paris Cedex 05, France
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21
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Kinetic and spectroscopic characterization of the putative monooxygenase domain of human MICAL-1. Arch Biochem Biophys 2011; 515:1-13. [PMID: 21864500 DOI: 10.1016/j.abb.2011.08.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2011] [Revised: 08/08/2011] [Accepted: 08/09/2011] [Indexed: 12/30/2022]
Abstract
MICALs form a conserved multidomain protein family essential for cytoskeletal rearrangements. To complement structural information available, we produced the FAD-containing monooxygenase-like domain of human MICAL-1 (MICAL-MO) in forms differing for the presence and location of a His-tag, which only influences the protein yields. The K(m) for NADPH of the NADPH oxidase reaction is sensitive to ionic strength and type of ions. The apparent k(cat) (pH 7) is limited by enzyme reduction by NADPH, which occurs without detectable intermediates, as established by anaerobic rapid reaction experiments. The sensitivity to ionic strength and type of ions and the pH dependence of the steady-state kinetic parameters extend MICAL-MO similarity with enzymes of the p-hydroxybenzoate hydroxylase class at the functional level. The reaction is also sensitive to solvent viscosity, providing a tool to monitor the conformational changes predicted to occur during turnover. Finally, it was confirmed that MICAL-MO promotes actin depolymerization, and it was shown that F-actin, but not G-actin, stimulates NADPH oxidation by increasing k(cat) and k(cat)/K(NADPH) (≈5 and ≈200-fold, respectively) with an apparent K(m) for actin of 4.7μM, under conditions that stabilize F-actin. The time-course of NADPH oxidation shows substrate recycling, indicating the possible reversibility of MICAL effect.
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22
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Di Paolo ML, Lunelli M, Fuxreiter M, Rigo A, Simon I, Scarpa M. Active site residue involvement in monoamine or diamine oxidation catalysed by pea seedling amine oxidase. FEBS J 2011; 278:1232-43. [PMID: 21294844 DOI: 10.1111/j.1742-4658.2011.08044.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The structures of copper amine oxidases from various sources show good similarity, suggesting similar catalytic mechanisms for all members of this enzyme family. However, the optimal substrates for each member differ, depending on the source of the enzyme and its location. The structural factors underlying substrate selectivity still remain to be discovered. With this in view, we examined the kinetic behaviour of pea seedling amine oxidase with cadaverine and hexylamine, the first bearing two, and the second only one, positively charged amino group. The dependence of K(m) and catalytic constant (k(c)) values on pH, ionic strength and temperature indicates that binding of the monoamine is driven by hydrophobic interactions. Instead, binding of the diamine is strongly facilitated by electrostatic factors, controlled by polar side-chains and two titratable residues present in the active site. The position of the docked substrate is also essential for the participation of titratable amino acid residues in the following catalytic steps. A new mechanistic model explaining the substrate-dependent kinetics of the reaction is discussed.
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23
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Bonaiuto E, Lunelli M, Scarpa M, Vettor R, Milan G, Di Paolo ML. A structure-activity study to identify novel and efficient substrates of the human semicarbazide-sensitive amine oxidase/VAP-1 enzyme. Biochimie 2010; 92:858-68. [PMID: 20298739 DOI: 10.1016/j.biochi.2010.03.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2010] [Accepted: 03/10/2010] [Indexed: 01/09/2023]
Abstract
Kinetic studies were performed with various alkanamines as "substrate probes" of the properties of the active site of the human semicarbazide-sensitive amine oxidase/vascular adhesion protein-1 (SSAO/VAP-1). We found that the enzyme-substrate recognition step is mainly controlled by apolar interactions and that a "good" substrate has a molecular structure containing a long aliphatic chain and a second positive charge at a distance greater than 12 A from the reactive amino group. In this context, we identified a novel substrate for the human SSAO/VAP-1, 1,12-diaminododecane (DIADO), which is characterised by the highest catalytic efficiency reported to date in comparison to the prototypic substrate benzylamine. Computational docking studies revealed the structural basis of this behaviour, highlighting the key role played by Lys393 in hindering substrate docking. Maximum SSAO/VAP-1 activity is reached at relatively low concentrations of DIADO (10-30 microM), and, in these conditions, it has good selectivity: it is a good substrate of SSAO/VAP-1 but not of human adipocyte monoamine oxidases or pig kidney diamine oxidase. From these findings, it appears that DIADO can be used as a new substrate for human SSAO/VAP-1 to elicit glucose transport into adipocytes, and may consequently have potential pharmacological applications in the design of anti-diabetic agents.
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Affiliation(s)
- Emanuela Bonaiuto
- Department of Biological Chemistry, University of Padova, Via G. Colombo, 3, 35131 Padova, Italy
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24
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Fedosova NU, Esmann M. Nucleotide binding to Na,K-ATPase: pK values of the groups affecting the high affinity site. Biochemistry 2007; 46:9116-22. [PMID: 17630772 DOI: 10.1021/bi602429a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Investigation of the ionic strength effect on the interactions between nucleotides (ATP and ADP) and Na,K-ATPase in a broad pH range was aimed at revealing pK values of the charged groups of the interacting species. Ionic strength experiments suggested that an amino acid residue with a pK > 8.0 is part of the protein binding site. A combination of equilibrium and transient experiments at various pH values allowed for the characterization of the groups electrostatically involved in either the association process (kon) or the stability of the preformed complexes (koff). Two groups (pK1 = 6.7 and pK2 = 8.4) appear to be important for the proper organization of the binding site and, therefore, the association reaction. Moreover, deprotonation of the basic group completely precludes association. pH dependencies of the dissociation rate constants for ATP and ADP are very different. An increase in pH from 5 to 9.5 induces a 9-fold increase in koff for ATP, whereas koff for ADP decreases 4-fold between pH 5 and 8, and decreases further in the alkaline region. A comparison of the pH dependencies for koff for ATP and ADP suggests two effects: (1) at acidic pH, the value of the total negative charge of the nucleotide determines the tightness of binding; and (2) short-range interactions involving the terminal phosphate group are important for nucleotide dissociation from the site. The difference in the pH dependencies of koff for the nucleotides suggests the existence of positive charges in close proximity to Asp369, relieving the repulsion between the gamma-phosphate of ATP and Asp369.
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Affiliation(s)
- Natalya U Fedosova
- Department of Biophysics, Institute of Physiology and Biophysics, University of Aarhus, Ole Worms Allé 1185, DK-8000 Aarhus C, Denmark.
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25
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Montes MR, González-Lebrero RM, Garrahan PJ, Rossi RC. Eosin Fluorescence Changes during Rb+Occlusion in the Na+/K+-ATPase†. Biochemistry 2006; 45:13093-100. [PMID: 17059226 DOI: 10.1021/bi060778i] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We used suspensions of partially purified Na(+)/K(+)-ATPase from pig kidney to compare the effects of Rb(+), as a K(+) congener, on the time course and on the equilibrium values of eosin fluorescence and of Rb(+) occlusion. Both sets of data were collected under identical conditions in the same enzyme preparations. The incubation media lacked ATP so that all changes led to an equilibrium distribution between enzyme conformers with and without bound eosin and with and without bound or occluded Rb(+). Results showed that as Rb(+) concentration was increased, the equilibrium value of fluorescence decreased and occlusion increased along rectangular hyperbolas with similar half-maximal values. The time courses of attainment of equilibrium showed an initial phase which was so quick as to fall below the time resolution of our rapid-mixing apparatus. This phase was followed by the sum of at least two exponential functions of time. In the case of fluorescence the fast exponential term accounted for a larger fraction of the time course than in the case of occlusion. Comparison between experimental and simulated results suggests that fluorescence changes express a process that is coupled to Rb(+) occlusion but that is completed before occlusion reaches equilibrium.
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Affiliation(s)
- Mónica R Montes
- Instituto de Química y Fisicoquímica Biológicas, Departamento de Química Biológica, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, C1113AAD Buenos Aires, Argentina
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26
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Ayuyan AG, Sokolov VS, Lenz AA, Apell HJ. Effect of chaotropic anions on the sodium transport by the Na,K-ATPase. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2005; 35:247-54. [PMID: 16292645 DOI: 10.1007/s00249-005-0031-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2005] [Revised: 10/14/2005] [Accepted: 10/18/2005] [Indexed: 11/28/2022]
Abstract
The effect of choline iodide, bromide and chloride on the kinetics of the electrogenic sodium transport by the Na,K-ATPase was investigated in a model system of ATPase-containing membrane fragments adsorbed on the lipid bilayer membrane. The kinetic parameters of Na(+) transport were determined from short circuit currents after fast release of ATP from its caged precursor. The falling phase of the current transients could be fitted by a single exponential with the time constant, tau (2). Its temperature dependence allowed an estimation of the activation energy of the rate-limiting reaction step, the conformation transition E(1)/E(2). Choline iodide and bromide caused a decrease of the activation energy as well as the overall rate of the process expressed as the pre-exponential factor A of the Arrhenius equation. If choline iodide or bromide were present on the cytoplasmic and extracellular sides of the protein, the temperature dependent changes were more pronounced than when present on the cytoplasmic side only. These results can be explained by an effect of the anions on water structure on the extracellular surface of the protein, where a deep access channel connects the ion-binding sites with the solution. Chloride ions also caused a deceleration of the electrogenic transport, however, in contrast to iodide or bromide, they did not affect the activation energy, and were more effective when added on the cytoplasmic side. This effect can be explained by asymmetric screening of the negative surface charges which leads to a transmembrane electric potential that modifies the ion transfer.
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Affiliation(s)
- Artem G Ayuyan
- A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 31 Leninski Prospect, 119071 Moscow, Russia
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27
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Di Stasio E. Anionic regulation of biological systems: the special role of chloride in the coagulation cascade. Biophys Chem 2005; 112:245-52. [PMID: 15572255 DOI: 10.1016/j.bpc.2004.07.026] [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] [Received: 03/11/2004] [Accepted: 07/01/2004] [Indexed: 10/26/2022]
Abstract
The discovery that previously unidentified allosteric properties of several proteins, such as fibrinogen and myoglobin, can be triggered by anions binding, has suggested the possibility to design a new "active" role of chloride in the modulation of a broad range of biological systems. The molecular bases of the anions binding to proteins depends by their charge density in turn regulating the ability to bind water molecules and interact with basic groups on proteins. This review reports the role of the physiologically relevant chloride, and of other anions, in the regulation of several proteins, with special attention to the coagulation cascade. Moreover, possible mechanisms of modification of plasma, intra- or extracellular chloride concentration are listed.
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Affiliation(s)
- Enrico Di Stasio
- Istituto di Biochimica e Biochimica Clinica, Università Cattolica del Sacro Cuore, Largo F. Vito no. 1, 00168 Rome, Italy.
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28
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Esmann M, Fedosova NU. Anion interactions with Na,K-ATPase: simultaneous binding of nitrate and eosin. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2004; 33:683-90. [PMID: 15565441 DOI: 10.1007/s00249-004-0411-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2003] [Revised: 04/02/2004] [Accepted: 04/05/2004] [Indexed: 11/27/2022]
Abstract
Nucleotide binding affinity to Na,K-ATPase is reduced by a number of anions such as nitrate and perchlorate in comparison with affinity in the presence of chloride (all with sodium as the cation). The reduction correlates with the position of these anions in the Hofmeister series. Transient kinetic experiments using the fluorescent dye eosin-which binds to the nucleotide site of the Na,K-ATPase-show that simultaneous anion binding, exemplified with nitrate, and eosin binding is possible. The effect of nitrate on eosin binding is reflected in a decreased binding-rate constant and an increased dissociation rate constant, leading to a decreased equilibrium binding constant for eosin. Since eosin binding is analogous with nucleotide binding to Na,K-ATPase, the results suggest the simultaneous presence of nucleotide and anion binding sites.
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Affiliation(s)
- Mikael Esmann
- Department of Biophysics, University of Aarhus, Ole Worms Allé 185, 8000, Aarhus, Denmark.
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29
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Abstract
The role of ionized groups in biological systems is determined by their affinity for water [Biophys. J. 72 (1997) 65-76]. The tightly bound water associated with biologically important ions increases their apparent size. We define the apparent dynamic hydration number of an ion here as the number of tightly bound water molecules that must be assigned to the ion to explain its apparent molecular weight on a Sephadex G-10 size exclusion column, and report the first accurate determination of tightly bound water for 23 ions of biological significance, including H(+) and HO(-). We also calculate the radius of the equivalent hydrated sphere (r(h)) for each ion. We find that the ratio of the hydrated volumes of two ions approximates the ratio of the square of the charges of the same two ions. Since the 'ionic strength' of the solution also depends upon the square of the charges on the ions, our results suggest that ionic strength effects may largely arise from local effects related to the hydrated volume of the ion--that is, from space filling, osmotic, water activity, surface tension and hydration shell overlap effects rather than from long-range electric field effects.
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Affiliation(s)
- Michael Y Kiriukhin
- Department of Biochemistry and Molecular Biology, University of Maryland Medical School, Baltimore, MD 21201-1503, USA
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30
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Fedosova NU, Champeil P, Esmann M. Nucleotide Binding to Na,K-ATPase: The Role of Electrostatic Interactions. Biochemistry 2002; 41:1267-73. [PMID: 11802726 DOI: 10.1021/bi011887u] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The contribution of electrostatic forces to the interaction of Na,K-ATPase with adenine nucleotides was investigated by studying the effect of ionic strength on nucleotide binding. At pH 7.0 and 20 degrees C, there was a qualitative correlation between the equilibrium dissociation constant (K(d)) values for ATP, ADP, and MgADP and their total charges. All K(d) values increased with increasing ionic strength. According to the Debye-Hückel theory, this suggests that the nucleotide binding site and its ligands have "effective" charges of opposite signs. However, quantitative analysis of the dependence on ionic strength shows that the product of the effective electrostatic charges on the ligand and the binding site is the same for all nucleotides, and is therefore independent of the total charge of the nucleotide. The data suggest that association of nucleotides with Na,K-ATPase is governed by a partial charge rather than the total charge of the nucleotide. This charge, interacting with positive charges on the protein, is probably the one corresponding to the alpha-phosphate of the nucleotide. Dissociation rate constants measured in complementary transient kinetic experiments were 13 s(-1) for ATP and 27 s(-1) for ADP, independent of the ionic strength in the range 0.1-0.5 M. This implies similar association rate constants for the two nucleotides (about 40 x 10(6) M(-1) s(-1) at I = 0.1 M). The results suggest that long-range Coulombic forces, affecting association rates, are not the main contributors to the observed differences in affinities, and that local interactions, affecting dissociation rates, may play an even greater role.
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Affiliation(s)
- Natalya U Fedosova
- Department of Biophysics, University of Aarhus, Ole Worms Allé185, DK-8000 Aarhus C, Denmark.
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31
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Genet S, Costalat R, Burger J. The influence of plasma membrane electrostatic properties on the stability of cell ionic composition. Biophys J 2001; 81:2442-57. [PMID: 11606261 PMCID: PMC1301715 DOI: 10.1016/s0006-3495(01)75891-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
An electro-osmotic model is developed to examine the influence of plasma membrane superficial charges on the regulation of cell ionic composition. Assuming membrane osmotic equilibrium, the ion distribution predicted by Gouy-Chapman-Grahame (GCG) theory is introduced into ion transport equations, which include a kinetic model of the Na/K-ATPase based on the stimulation of this ion pump by internal Na(+) ions. The algebro-differential equation system describing dynamics of the cell model has a unique resting state, stable with respect to finite-sized perturbations of various types. Negative charges on the membrane are found to greatly enhance relaxation toward steady state following these perturbations. We show that this heightened stability stems from electrostatic interactions at the inner membrane side that shift resting state coordinates along the sigmoidal activation curve of the sodium pump, thereby increasing the pump sensitivity to internal Na(+) fluctuations. The accuracy of electrostatic potential description with GCG theory is proved using an alternate formalism, based on irreversible thermodynamics, which shows that pressure contribution to ion potential energy is negligible in electrostatic double layers formed at the surfaces of biological membranes. We discuss implications of the results regarding a reliable operation of ionic process coupled to the transmembrane electrochemical gradient of Na(+) ions.
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Affiliation(s)
- S Genet
- Institut National de la Santé et de la Recherche Médicale U. 483, Université Pierre et Marie Curie, 75252 Paris Cedex 05, France.
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32
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Cornelius F. Modulation of Na,K-ATPase and Na-ATPase activity by phospholipids and cholesterol. I. Steady-state kinetics. Biochemistry 2001; 40:8842-51. [PMID: 11467945 DOI: 10.1021/bi010541g] [Citation(s) in RCA: 142] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The effects of phospholipid acyl chain length (n(c)), degree of acyl chain saturation, and cholesterol on Na,K-ATPase reconstituted into liposomes of defined lipid composition are described. The optimal acyl chain length of monounsaturated phosphatidylcholine in the absence of cholesterol was found to be 22 but decreased to 18 in the presence of 40 mol % cholesterol. This indicates that the hydrophobic matching of the lipid bilayer and the transmembrane hydrophobic core of the membrane protein is a crucial parameter in supporting optimal Na,K-ATPase activity. In addition, the increased bilayer order induced by both cholesterol and saturated phospholipids could be important for the conformational mobility of the Na,K-ATPase changing the distribution of conformations. Lipid fluidity was important for several parameters of reconstitution, e.g., the amount of protein inserted and the orientation in the liposomes. The temperature dependence of the Na,K-ATPase as well of the Na-ATPase reactions depends both on phospholipid acyl chain length and on cholesterol. Cholesterol increased significantly both the enthalpy of activation and entropy of activation for Na,K-ATPase activity and Na-ATPase activity of Na,K-ATPase reconstituted with monounsaturated phospholipids. In the presence of cholesterol the free energy of activation was minimum at a lipid acyl chain length of 18, the same that supported maximum turnover. In the case of ATPase reconstituted without cholesterol, the minimum free energy of activation and the maximum turnover both shifted to longer acyl chain lengths of about 22.
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Affiliation(s)
- F Cornelius
- Department of Biophysics, University of Aarhus, DK-8000 Denmark.
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Du W, Liu WS, Payne DJ, Doyle ML. Synergistic inhibitor binding to Streptococcus pneumoniae 5-enolpyruvylshikimate-3-phosphate synthase with both monovalent cations and substrate. Biochemistry 2000; 39:10140-6. [PMID: 10956002 DOI: 10.1021/bi000890v] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The inhibitor binding synergy mechanism of the bi-substrate enzyme Streptococcus pneumoniae 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) has been investigated with a linkage thermodynamics strategy, involving direct binding experiments of one ligand conducted over a range of concentration of the other. The results demonstrate that binding of the inhibitor glyphosate (GLP) is highly synergistic with both a natural substrate shikimate-3-phosphate (S3P) and activating monovalent cations. The synergy between GLP and S3P binding was determined to be 1600-fold and is in qualitative agreement with previous work on Escherichia coli EPSPS. The binding molar ratios of S3P and GLP were measured as 1.0 and 0.7 per EPSPS, respectively. Monovalent cations that have been shown previously to stimulate S. pneumoniae EPSPS catalytic activity and its inhibition by GLP were found here to exhibit a similar rank-order with respect to their measured GLP binding synergies (ranging from 0 to > or =3000-fold increase in GLP affinity). The cation specificity and the sub-millimolar concentrations where these effects occur strongly suggest the presence of a specific cation binding site. Analytical ultracentrifugation data ruled out GLP-binding synergy mechanisms that derive from, or are influenced by, changes in oligomerization of S. pneumoniae EPSPS. Rather, the data are most consistent with an allosteric mechanism involving changes in tertiary structure. The results provide a quantitative framework for understanding the inhibitor binding synergies in S. pneumoniae EPSPS and implicate the presence of a specific cation binding regulatory site. The findings will help to guide rational design of novel antibiotics targeting bacterial EPSPS enzymes.
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Affiliation(s)
- W Du
- Department of Anti-Infectives Research, SmithKline Beecham Pharmaceuticals, Collegeville, Pennsylvania 19426, USA
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34
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Vilsen B. Mutant Phe788 --> Leu of the Na+,K+-ATPase is inhibited by micromolar concentrations of potassium and exhibits high Na+-ATPase activity at low sodium concentrations. Biochemistry 1999; 38:11389-400. [PMID: 10471289 DOI: 10.1021/bi990951t] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mutant Phe788 --> Leu of the rat kidney Na+,K(+)-ATPase was expressed in COS cells to active-site concentrations between 40 and 60 pmol/mg of membrane protein. Analysis of the functional properties showed that the discrimination between Na+ and K+ on the two sides of the system is severely impaired in the mutant. Micromolar concentrations of K+ inhibited ATP hydrolysis (K(0.5) for inhibition 107 microM for the mutant versus 76 mM for the wild-type at 20 mM Na+), and at 20 mM K+, the molecular turnover number for Na+,K(+)-ATPase activity was reduced to 11% that of the wild-type. This inhibition was counteracted by Na+ in high concentrations, and in the total absence of K+, the mutant catalyzed Na(+)-activated ATP hydrolysis ("Na(+)-ATPase activity") at an extraordinary high rate corresponding to 86% of the maximal Na+,K(+)-ATPase activity. The high Na(+)-ATPase activity was accounted for by an increased rate of K(+)-independent dephosphorylation. Already at 2 mM Na+, the dephosphorylation rate of the mutant was 8-fold higher than that of the wild-type, and the maximal rate of Na(+)-induced dephosphorylation amounted to 61% of the rate of K(+)-induced dephosphorylation. The cause of the inhibitory effect of K+ on ATP hydrolysis in the mutant was an unusual stability of the K(+)-occluded E2(K2) form. Hence, when E2(K2) was formed by K+ binding to unphosphorylated enzyme, the K(0.5) for K+ occlusion was close to 1 microM in the mutant versus 100 microM in the wild-type. In the presence of 100 mM Na+ to compete with K+ binding, the K(0.5) for K+ occlusion was still 100-fold lower in the mutant than in the wild-type. Moreover, relative to the wild-type, the mutant exhibited a 6-7-fold reduced rate of release of occluded K+, a 3-4-fold increased apparent K+ affinity in activation of the pNPPase reaction, a 10-11-fold lower apparent ATP affinity in the Na+,K(+)-ATPase assay with 250 microM K+ present (increased K(+)-ATP antagonism), and an 8-fold reduced apparent ouabain affinity (increased K(+)-ouabain antagonism).
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Affiliation(s)
- B Vilsen
- Department of Physiology, University of Aarhus, Denmark.
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Gropp T, Brustovetsky N, Klingenberg M, Müller V, Fendler K, Bamberg E. Kinetics of electrogenic transport by the ADP/ATP carrier. Biophys J 1999; 77:714-26. [PMID: 10423420 PMCID: PMC1300366 DOI: 10.1016/s0006-3495(99)76926-2] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
The electrogenic transport of ATP and ADP by the mitochondrial ADP/ATP carrier (AAC) was investigated by recording transient currents with two different techniques for performing concentration jump experiments: 1) the fast fluid injection method: AAC-containing proteoliposomes were adsorbed to a solid supported membrane (SSM), and the carrier was activated via ATP or ADP concentration jumps. 2) BLM (black lipid membrane) technique: proteoliposomes were adsorbed to a planar lipid bilayer, while the carrier was activated via the photolysis of caged ATP or caged ADP with a UV laser pulse. Two transport modes of the AAC were investigated, ATP(ex)-0(in) and ADP(ex)-0(in). Liposomes not loaded with nucleotides allowed half-cycles of the ADP/ATP exchange to be studied. Under these conditions the AAC transports ADP and ATP electrogenically. Mg(2+) inhibits the nucleotide transport, and the specific inhibitors carboxyatractylate (CAT) and bongkrekate (BKA) prevent the binding of the substrate. The evaluation of the transient currents yielded rate constants of 160 s(-1) for ATP and >/=400 s(-1) for ADP translocation. The function of the carrier is approximately symmetrical, i.e., the kinetic properties are similar in the inside-out and right-side-out orientations. The assumption from previous investigations, that the deprotonated nucleotides are exclusively transported by the AAC, is supported by further experimental evidence. In addition, caged ATP and caged ADP bind to the carrier with similar affinities as the free nucleotides. An inhibitory effect of anions (200-300 mM) was observed, which can be explained as a competitive effect at the binding site. The results are summarized in a transport model.
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Affiliation(s)
- T Gropp
- Max-Planck-Institut für Biophysik, 60596 Frankfurt, Germany
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Ganea C, Babes A, Lüpfert C, Grell E, Fendler K, Clarke RJ. Hofmeister effects of anions on the kinetics of partial reactions of the Na+,K+-ATPase. Biophys J 1999; 77:267-81. [PMID: 10388756 PMCID: PMC1300328 DOI: 10.1016/s0006-3495(99)76888-8] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The effects of lyotropic anions, particularly perchlorate, on the kinetics of partial reactions of the Na+,K+-ATPase from pig kidney were investigated by two different kinetic techniques: stopped flow in combination with the fluorescent label RH421 and a stationary electrical relaxation technique. It was found that 130 mM NaClO4 caused an increase in the Kd values of both the high- and low-affinity ATP-binding sites, from values of 7.0 (+/- 0.6) microM and 143 (+/- 17) microM in 130 mM NaCl solution to values of 42 (+/- 3) microM and 660 (+/- 100) microM in 130 mM NaClO4 (pH 7.4, 24 degrees C). The half-saturating concentration of the Na+-binding sites on the E1 conformation was found to decrease from 8-10 mM in NaCl to 2.5-3.5 mM in NaClO4 solution. The rate of equilibration of the reaction, E1P(Na+)3 left arrow over right arrow E2P + 3Na+, decreased from 393 (+/- 51) s-1 in NaCl solution to 114 (+/- 15) s-1 in NaClO4. This decrease is attributed predominantly to an inhibition of the E1P(Na+)3 --> E2P(Na+)3 transition. The effects can be explained in terms of electrostatic interactions due to perchlorate binding within the membrane and/or protein matrix of the Na+,K+-ATPase membrane fragments and alteration of the local electric field strength experienced by the protein. The kinetic results obtained support the conclusion that the conformational transition E1P(Na+)3 --> E2P(Na+)3 is a major charge translocating step of the pump cycle.
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Affiliation(s)
- C Ganea
- Department of Biophysics, C. Davila Medical University, 76241 Bucharest, Romania
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Clarke RJ, Lüpfert C. Influence of anions and cations on the dipole potential of phosphatidylcholine vesicles: a basis for the Hofmeister effect. Biophys J 1999; 76:2614-24. [PMID: 10233076 PMCID: PMC1300231 DOI: 10.1016/s0006-3495(99)77414-x] [Citation(s) in RCA: 178] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Anions and cations have long been recognized to be capable of modifying the functioning of various membrane-related physiological processes. Here, a fluorescent ratio method using the styrylpyridinium dyes, RH421 and di-8-ANEPPS, was applied to determine the effect of a range of anions and cations on the intramembrane dipole potential of dimyristoylphosphatidylcholine vesicles. It was found that certain anions cause a decrease in the dipole potential. This could be explained by binding within the membrane, in support of a hypothesis originally put forward by A. L. Hodgkin and P. Horowicz [1960, J. Physiol. (Lond.) 153:404-412.] The effectiveness of the anions in reducing the dipole potential was found to be ClO4- > SCN- > I- > NO3- > Br- > Cl- > F- > SO42-. This order could be modeled by a partitioning of ions between the membrane and the aqueous phase, which is controlled predominantly by the Gibbs free energy of hydration. Cations were also found to be capable of reducing the dipole potential, although much less efficiently than can anions. The effects of the cations was found to be trivalent > divalent > monovalent. The cation effects were attributed to binding to a specific polar site on the surface of the membrane. The results presented provide a molecular basis for the interpretation of the Hofmeister effect of lyotropic anions on ion transport proteins.
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Affiliation(s)
- R J Clarke
- Department of Biophysical Chemistry, Max-Planck-Institut für Biophysik, Kennedyallee 70, D-60596 Frankfurt am Main, Germany
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38
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Champeil P, Menguy T, Soulié S, Juul B, de Gracia AG, Rusconi F, Falson P, Denoroy L, Henao F, le Maire M, Moller JV. Characterization of a protease-resistant domain of the cytosolic portion of sarcoplasmic reticulum Ca2+-ATPase. Nucleotide- and metal-binding sites. J Biol Chem 1998; 273:6619-31. [PMID: 9506958 DOI: 10.1074/jbc.273.12.6619] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Treatment of rabbit sarcoplasmic reticulum Ca2+-ATPase with a variety of proteases, including elastase, proteinase K, and endoproteinases Asp-N and Glu-C, results in accumulation of soluble fragments starting close to the ATPase phosphorylation site Asp351 and ending in the Lys605-Arg615 region, well before the conserved sequences generally described as constituting the "hinge" region of this P-type ATPase (residues 670-760). These fragments, designated as p29/30, presumably originate from a relatively compact domain of the cytoplasmic head of the ATPase. They retain two structural characteristics of intact Ca2+-ATPase as follows: high sensitivity of peptidic bond Arg505-Ala506 to trypsin cleavage, and high reactivity of lysine residue Lys515 toward the fluorescent label fluorescein 5'-isothiocyanate. Regarding functional properties, these fragments retain the ability to bind nucleotides, although with reduced affinity compared with intact Ca2+-ATPase. The fragments also bind Nd3+ ions, leaving open the possibility that these fragments could contain the metal-binding site(s) responsible for the inhibitory effect of lanthanide ions on ATPase activity. The p29/30 soluble domain, like similar proteolytic fragments that can be obtained from other P-type ATPases, may be useful for obtaining three-dimensional structural information on the cytosolic portion of these ATPases, with or without bound nucleotides. From our findings we infer that a real hinge region with conformational flexibility is located at the C-terminal boundary of p29/30 (rather than in the conserved region of residues 670-760); we also propose that the ATP-binding cleft is mainly located within the p29/30 domain, with the phosphorylation site strategically located at the N-terminal border of this domain.
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Affiliation(s)
- P Champeil
- URA 2096 (CNRS) and Section de Biophysique des Protéines et des Membranes, Département de Biologie Cellulaire et Moléculaire, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
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39
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Affiliation(s)
- J G Nørby
- Department of Biophysics, University of Aarhus, Denmark.
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40
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Esmann M, Fedosova NU. Eosin as a probe for conformational transitions and nucleotide binding in Na,K-ATPase. Ann N Y Acad Sci 1997; 834:310-21. [PMID: 9405817 DOI: 10.1111/j.1749-6632.1997.tb52261.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- M Esmann
- Department of Biophysics, University of Aarhus, Denmark.
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41
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De Weer P. Keeping it simple: kinetic models for the sodium pump. J Gen Physiol 1997; 109:525-6. [PMID: 9154901 PMCID: PMC2217065 DOI: 10.1085/jgp.109.5.525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Affiliation(s)
- P De Weer
- Department of Physiology, University of Pennsylvania, Philadelphia 19104-6085, USA
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