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Li M, An H, Wang W, Wei D. Biomolecular Markers of Brain Aging. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1419:111-126. [PMID: 37418210 DOI: 10.1007/978-981-99-1627-6_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 07/08/2023]
Abstract
Characterized by the gradual loss of physiological integrity, impaired function, and increased susceptibility to death, aging is considered the primary risk factor for major human diseases, such as cancer, diabetes, cardiovascular disorders, and neurodegenerative diseases. The time-dependent accumulation of cellular damage is widely considered the general cause of aging. While the mechanism of normal aging is still unresolved, researchers have identified different markers of aging, including genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient-sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and altered intercellular communication. Theories of aging can be divided into two categories: (1) aging is a genetically programmed process, and (2) aging is a random process caused by gradual damage to the organism over time as a result of its vital activities. Aging affects the entire human body, and aging of the brain is undoubtedly different from all other organs, as neurons are highly differentiated postmitotic cells, and the lifespan of most neurons in the postnatal period is equal to the lifespan of the brain. In this chapter, we discuss the conserved mechanisms of aging that may underlie the changes observed in the aging brain, with a focus on mitochondrial function and oxidative stress, autophagy and protein turnover, insulin/IGF signaling, target of rapamycin (TOR) signaling, and sirtuin function.
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Affiliation(s)
- Min Li
- State Key Laboratory of Cognitive Neuroscience and Learning, Faculty of Psychology, Beijing Normal University, Beijing, China
- Beijing Aging Brain Rejuvenation Initiative (BABRI) Centre, Beijing Normal University, Beijing, China
| | - Haiting An
- Beijing Aging Brain Rejuvenation Initiative (BABRI) Centre, Beijing Normal University, Beijing, China
- Beijing Neurosurgical Institute, Beijing Tian Tan Hospital, Capital Medical University, Beijing, China
| | - Wenxiao Wang
- Beijing Aging Brain Rejuvenation Initiative (BABRI) Centre, Beijing Normal University, Beijing, China
- School of Systems Science, Beijing Normal University, Beijing, China
| | - Dongfeng Wei
- Beijing Aging Brain Rejuvenation Initiative (BABRI) Centre, Beijing Normal University, Beijing, China
- Institute of Basic Research in Clinical Medicine, China Academy of Chinese Medical Sciences, Beijing, China
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Apell HJ, Roudna M. Partial Reactions of the Na,K-ATPase: Determination of Activation Energies and an Approach to Mechanism. J Membr Biol 2020; 253:631-645. [PMID: 33184678 PMCID: PMC7688194 DOI: 10.1007/s00232-020-00153-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Accepted: 11/05/2020] [Indexed: 11/26/2022]
Abstract
Abstract Kinetic experiments were performed with preparations of kidney Na,K-ATPase in isolated membrane fragments or reconstituted in vesicles to obtain information of the activation energies under turnover conditions and for selected partial reactions of the Post-Albers pump cycle. The ion transport activities were detected with potential or conformation sensitive fluorescent dyes in steady-state or time-resolved experiments. The activation energies were derived from Arrhenius plots of measurements in the temperature range between 5 °C and 37 °C. The results were used to elaborate indications of the respective underlying rate-limiting reaction steps and allowed conclusions to be drawn about possible molecular reaction mechanisms. The observed consequent alteration between ligand-induced reaction and conformational relaxation steps when the Na,K-ATPase performs the pump cycle, together with constraints set by thermodynamic principles, provided restrictions which have to be met when mechanistic models are proposed. A model meeting such requirements is presented for discussion. Graphic Abstract ![]()
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Affiliation(s)
- Hans-Jürgen Apell
- Department of Biology, University of Konstanz, 78464, Konstanz, Germany.
| | - Milena Roudna
- Department of Biology, University of Konstanz, 78464, Konstanz, Germany
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Abstract
Reconstitution of P-type ATPases in unilamellar liposomes is a useful technique to study functional properties of these active ion transporters. Experiments with such liposomes provide an easy access to substrate-binding affinities of the ion pumps as well as to the lipid and temperature dependence of the pump current. Here, we describe two reconstitution methods by dialysis and the use of potential-sensitive fluorescence dyes to study transport properties of two P-type ATPases, the Na,K-ATPase from rabbit kidney and the K(+)-transporting KdpFABC complex from E. coli. Several techniques are introduced how the measured fluorescence signals may be analyzed to gain information on properties of the ion pumps.
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Affiliation(s)
- Hans-Jürgen Apell
- Department of Biology, University of Konstanz, 635, Universitätsstr. 10, Konstanz, 78464, Germany.
| | - Bojana Damnjanovic
- Department of Biology, University of Konstanz, 635, Universitätsstr. 10, Konstanz, 78464, Germany
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Structural lipid changes and Na + /K + -ATPase activity of gill cells' basolateral membranes during saltwater acclimation in sea lamprey ( Petromyzon marinus , L.) juveniles. Comp Biochem Physiol A Mol Integr Physiol 2015; 189:67-75. [DOI: 10.1016/j.cbpa.2015.07.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Revised: 07/29/2015] [Accepted: 07/29/2015] [Indexed: 02/02/2023]
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Mechanical Properties of Bilayer Lipid Membranes and Protein–Lipid Interactions. ACTA ACUST UNITED AC 2011. [DOI: 10.1016/b978-0-12-387721-5.00002-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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6
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Glutathione protects Lactobacillus sanfranciscensis against freeze-thawing, freeze-drying, and cold treatment. Appl Environ Microbiol 2010; 76:2989-96. [PMID: 20208023 DOI: 10.1128/aem.00026-09] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Lactobacillus sanfranciscensis DSM20451 cells containing glutathione (GSH) displayed significantly higher resistance against cold stress induced by freeze-drying, freeze-thawing, and 4 degrees C cold treatment than those without GSH. Cells containing GSH were capable of maintaining their membrane structure intact when exposed to freeze-thawing. In addition, cells containing GSH showed a higher proportion of unsaturated fatty acids in cell membranes upon long-term cold treatment. Subsequent studies revealed that the protective role of GSH against cryodamage of the cell membrane is partly due to preventing peroxidation of membrane fatty acids and protecting Na(+),K(+)-ATPase. Intracellular accumulation of GSH enhanced the survival and the biotechnological performance of L. sanfranciscensis, suggesting that the robustness of starters for sourdough fermentation can be improved by selecting GSH-accumulating strains. Moreover, the results of this study may represent a further example of mechanisms for stress responses in lactic acid bacteria.
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Bystriansky JS, Ballantyne JS. Gill Na+-K+-ATPase activity correlates with basolateral membrane lipid composition in seawater- but not freshwater-acclimated Arctic char (Salvelinus alpinus). Am J Physiol Regul Integr Comp Physiol 2006; 292:R1043-51. [PMID: 17038447 DOI: 10.1152/ajpregu.00189.2005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The successful migration of euryhaline teleost fish from freshwater to seawater requires the upregulation of gill Na+-K+-ATPase, an ion transport enzyme located in the basolateral membrane (BLM) of gill chloride cells. Following 39 days of seawater exposure, Arctic char had similar plasma sodium and chloride levels as individuals maintained in freshwater, indicating they had successfully acclimated to seawater. This acclimation was associated with an eightfold increase in gill Na+-K+-ATPase activity but only a threefold increase in gill Na+-K+-ATPase protein number, suggesting that other mechanisms may also modulate gill Na+-K+-ATPase activity. We therefore investigated the influence of membrane composition on Na+-K+-ATPase activity by examining the phospholipid, fatty acid, and cholesterol composition of the gill BLM from freshwater- and seawater-acclimated Arctic char. Mean gill BLM cholesterol content was significantly lower ( approximately 22%) in seawater-acclimated char. Gill Na+-K+-ATPase activity in individual seawater Arctic char was negatively correlated with BLM cholesterol content and positively correlated with %phosphatidylethanolamine and overall %18:2n6 (linoleic acid) content of the BLM, suggesting gill Na+-K+-ATPase activity of seawater-acclimated char may be modulated by the lipid composition of the BLM and may be especially sensitive to those parameters known to influence membrane fluidity. Na+-K+-ATPase activity of individual freshwater Arctic char was not correlated to any membrane lipid parameter measured, suggesting that different lipid-protein interactions may exist for char living in each environment.
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Affiliation(s)
- J S Bystriansky
- Department Integrative Biology, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
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8
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Else PL, Turner N, Hulbert AJ. The evolution of endothermy: role for membranes and molecular activity. Physiol Biochem Zool 2005; 77:950-8. [PMID: 15674769 DOI: 10.1086/422767] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/31/2003] [Indexed: 11/03/2022]
Abstract
On the basis of the comparative approach and three models of metabolism (endothermic and ectothermic vertebrates, body mass, and mammalian development), we suggest that a few common cellular processes, linked either directly or indirectly to membranes, consume the majority of energy used by most organisms; that membranes act as pacemakers of metabolism through changes in lipid composition, altering membrane characteristics and the working environment of membrane proteins--specifically, that changes in the membrane environment similarly affect the molecular activities (specific rates of activity) of membrane-bound proteins; and that polyunsaturation of membranes increases whereas monounsaturation decreases the activity of membrane proteins. Experiments designed to test this theory using the sodium pump support this supposition. Potential mechanisms considered include fluidity, electrical fields, and related surface area requirements of lipids. In considering the evolution of endothermy in mammals, for example, if the first mammals were small, possibly nocturnal and active organisms, all these factors would favour increased polyunsaturation of membranes. Such changes (from monounsaturated to polyunsaturated membranes) would allow membranes to set the pace of metabolism in the evolution of endothermy.
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Affiliation(s)
- Paul L Else
- Department of Biomedical Science, Metabolic Research Centre, University of Wollongong, New South Wales 2522, Australia.
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Cohen E, Goldshleger R, Shainskaya A, Tal DM, Ebel C, le Maire M, Karlish SJD. Purification of Na+,K+-ATPase Expressed in Pichia pastoris Reveals an Essential Role of Phospholipid-Protein Interactions. J Biol Chem 2005; 280:16610-8. [PMID: 15708860 DOI: 10.1074/jbc.m414290200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Na+,K+-ATPase (porcine alpha/his10-beta) has been expressed in Pichia Pastoris, solubilized in n-dodecyl-beta-maltoside and purified to 70-80% purity by nickel-nitrilotriacetic acid chromatography combined with size exclusion chromatography. The recombinant protein is inactive if the purification is done without added phospholipids. The neutral phospholipid, dioleoylphosphatidylcholine, preserves Na+,K+-ATPase activity of protein prepared in a Na+-containing medium, but activity is lost in a K+-containing medium. By contrast, the acid phospholipid, dioleoylphosphatidylserine, preserves activity in either Na+- or K+-containing media. In optimal conditions activity is preserved for about 2 weeks at 0 degrees C. Both recombinant Na+,K+-ATPase and native pig kidney Na+,K+-ATPase, dissolved in n-dodecyl-beta-maltoside, appear to be mainly stable monomers (alpha/beta) as judged by size exclusion chromatography and sedimentation velocity. Na+,K+-ATPase activities at 37 degrees C of the size exclusion chromatography-purified recombinant and renal Na+,K+-ATPase are comparable but are lower than that of membrane-bound renal Na+,K+-ATPase. The beta subunit is expressed in Pichia Pastoris as two lightly glycosylated polypeptides and is quantitatively deglycosylated by endoglycosidase-H at 0 degrees C, to a single polypeptide. Deglycosylation inactivates Na+,K+-ATPase prepared with dioleoylphosphatidylcholine, whereas dioleoylphosphatidylserine protects after deglycosylation, and Na+,K+-ATPase activity is preserved. This work demonstrates an essential role of phospholipid interactions with Na+,K+-ATPase, including a direct interaction of dioleoylphosphatidylserine, and possibly another interaction of either the neutral or acid phospholipid. Additional lipid effects are likely. A role for the beta subunit in stabilizing conformations of Na+,K+-ATPase (or H+,K+-ATPase) with occluded K+ ions can also be inferred. Purified recombinant Na+,K+-ATPase could become an important experimental tool for various purposes, including, hopefully, structural work.
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Affiliation(s)
- Eytan Cohen
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovoth, Israel
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10
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Starke-Peterkovic T, Turner N, Else PL, Clarke RJ. Electric field strength of membrane lipids from vertebrate species: membrane lipid composition and Na+-K+-ATPase molecular activity. Am J Physiol Regul Integr Comp Physiol 2004; 288:R663-70. [PMID: 15539609 DOI: 10.1152/ajpregu.00434.2004] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Intramembrane electric field strength is a very likely determinant of the activity of ion-transporting membrane proteins in living cells. In the absence of any transmembrane electrical potential or surface potential, its magnitude is determined by the dipole potential of the membrane's lipid components and their associated water of hydration. Here we have used a fluorometric method to quantify the dipole potential of vesicles formed from lipids extracted from kidney and brain of 11 different animal species from four different vertebrate classes. The dipole potential was compared with the fatty acid composition and with the Na(+)-K(+)-ATPase molecular activity of each preparation. The magnitude of the dipole potential was found to be relatively constant across all animal species, i.e., 236-334 mV for vesicles prepared from the total membrane lipids and 223-256 mV for phospholipids alone. The significantly lower value for phospholipids alone is potentially related to the removal of cholesterol and/or other common soluble lipid molecules from the membrane. Surprisingly, no significant dependence of the dipole potential on fatty acid composition was found. This may, however, be due to concomitant compensatory variations in lipid head group composition. The molecular activity of the Na(+)-K(+)-ATPase was found to increase with increasing dipole potential. The fact that the dipole potential is maintained at a relatively constant value over a wide range of animal species suggests that it may play a fundamental role in ensuring correct ion pump conformation and function within the membrane.
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11
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Abstract
The Na(+)-K(+)-ATPase, or sodium pump, is the membrane-bound enzyme that maintains the Na(+) and K(+) gradients across the plasma membrane of animal cells. Because of its importance in many basic and specialized cellular functions, this enzyme must be able to adapt to changing cellular and physiological stimuli. This review presents an overview of the many mechanisms in place to regulate sodium pump activity in a tissue-specific manner. These mechanisms include regulation by substrates, membrane-associated components such as cytoskeletal elements and the gamma-subunit, and circulating endogenous inhibitors as well as a variety of hormones, including corticosteroids, peptide hormones, and catecholamines. In addition, the review considers the effects of a range of specific intracellular signaling pathways involved in the regulation of pump activity and subcellular distribution, with particular consideration given to the effects of protein kinases and phosphatases.
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Affiliation(s)
- A G Therien
- Department of Biochemistry, McGill University, Montreal, Quebec, Canada H3G 1A4
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12
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Friedrich T, Bamberg E, Nagel G. Na+,K(+)-ATPase pump currents in giant excised patches activated by an ATP concentration jump. Biophys J 1996; 71:2486-500. [PMID: 8913588 PMCID: PMC1233737 DOI: 10.1016/s0006-3495(96)79442-0] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The giant-patch technique was used to study the Na+,K(+)-ATPase in excised patches from rat or guinea pig ventricular myocytes. Na+,K(+)-pump currents showed a saturable ATP dependence with aK(m) of approximately 150 microM at 24 degrees C. The pump current can be completely abolished by ortho-vanadate. Dissociation of vanadate from the enzyme in the absence of extracellular Na+ was slow, with a Koff of 3.10(-4) S-1 (K1 approximately 0.5 microM, at 24 degrees C). Stationary currents were markedly dependent on intracellular pH, with a maximum at pH 7.9. Temperature-dependence measurements of the stationary pump current yielded an activation energy of approximately 100 kJ mol-1. Partial reactions in the transport cycle were investigated by generating ATP concentration jumps through photolytic release of ATP from caged ATP at pH 7.4 and 6.3. Transient outward currents were obtained at pH 6.3 with a fast rising phase followed by a slower decay to a stationary current. It was concluded that the fast rate constant of approximately 200 s-1 at 24 degrees C (pH 6.3) reflects a step rate-limiting the electrogenic Na+ release. Simulating the data with a simple three-state model enabled us to estimate the turnover rate under saturating substrate concentrations, yielding rates (at pH 7.4) of approximately 60 s-1 and 200 s-1 at 24 degrees C and 36 degrees C, respectively.
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Affiliation(s)
- T Friedrich
- Max-Planck-Institut für Biophysik, Frankfurt am Main, Germany
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13
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Dwight JF, Hendry BM. Effects of membrane incorporation of short-chain phospholipids on sodium pump function in human erthrocytes. Clin Chim Acta 1995; 243:73-85. [PMID: 8747515 DOI: 10.1016/0009-8981(95)06156-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Erythrocyte membrane incorporation of exogenous short-chain diacyl phosphatidylcholines (PC) has been quantified by gas chromatography of fatty acid methyl esters of extracted membrane lipids after incubation of cells with sonicated aqueous suspensions of PC. The PCs studied included didecanoyl PC (C10-PC), dilauroyl PC (C12-PC), dimyristoyl PC (C14-PC) and dipalmitoyl PC (C16-PC). PC incorporation of 10-15 mol% was achieved by incubation at 37 degrees C for 0.5-24 h. Control cells incubated in saline alone showed a progressive reduction in endogenous polyunsaturated acyl chain content. Incubation with C10-PC and C16-PC was associated with reductions in membrane cholesterol. Experiments were performed with mixtures of PC and cholesterol in order to minimise this effect. Short-chain PC incorporation was associated with increases in intracellular Na+ and reduced intracellular K+ concentrations. Sodium pump activity was measured as the ouabain-sensitive rate of 86Rb+ influx and was significantly reduced by all PCs tested; mean reductions were 13-30%. These results confirm that the sodium pump in situ is sensitive to lipid acyl chain composition.
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Affiliation(s)
- J F Dwight
- Department of Medicine, King's College School of Medicine and Dentistry, London, UK
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14
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Bühler R, Apell HJ. Sequential potassium binding at the extracellular side of the Na,K-pump. J Membr Biol 1995; 145:165-73. [PMID: 7563018 DOI: 10.1007/bf00237374] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Ion binding at the extracellular face of the Na,K-ATPase is electrogenic and can be monitored by the styryl dye RH 421 in membrane fragments containing a high density of the Na,K-pumps. The fluorescent probe is noncovalently bound to the membrane and responds to changes of the local electric field generated by binding or release of cations inside the protein. Due to the fact that K+ binding from the extracellular side is an electrogenic reaction, it is possible to detect the amount of ions bound to the pump as function of the aqueous concentration. The results are in contradiction to a second order reaction, i.e., a simultaneous binding of two K+ ions. A mathematical model is presented to discuss the nature of the two step binding process. On the basis of this model the data allow a quantitative distinction between binding of the first and the second K+ ion. The temperature dependence of ion binding has been investigated. At low temperatures the apparent dissociation constants differ significantly. In the temperature range above 20 degrees C the resulting apparent dissociation constants for both K+ ions merge and have values between 0.2 and 0.3 mM, which is consistent with previous experiments. The activation energy for the half saturating concentration of K+ is 22 kJ/mol. Additional analysis of the titration curve of K+ binding to the state P-E2 by the Hill equation yields a Hill coefficient, nHill, of 1.33, which is in agreement with previously published data.
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Affiliation(s)
- R Bühler
- Department of Biology, University of Konstanz, Germany
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15
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Veld GI, Driessen AJ, Konings WN. Bacterial solute transport proteins in their lipid environment. FEMS Microbiol Rev 1993; 12:293-314. [PMID: 8268004 DOI: 10.1111/j.1574-6976.1993.tb00024.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The cytoplasmic membrane of bacteria is a selective barrier that restricts entry and exit of solutes. Transport of solutes across this membrane is catalyzed by specific membrane proteins. Integral membrane proteins usually require specific lipids for optimal activity and are inhibited by other lipid species. Their activities are also sensitive to the lipid bilayer dynamics and physico-chemical state. Bacteria can adapt to changes in the environments (respective temperature, hydrostatic pressure, and pH) by altering the lipid composition of the membrane. Homeoviscous adaptation results in the maintenance of the liquid-crystalline phase through alterations in the degree of acyl chain saturation and branching, acyl chain length and the sterol content of the membrane. Homeophasic adaptation prevents the formation of non-bilayer phases, which would disrupt membrane organization and increase permeability. A balance is maintained between the lamellar phase, preferring lipids, and those that adopt a non-bilayer organization. As a result, the membrane proteins are optimally active under physiological conditions. The molecular basis of lipid-protein interactions is still obscure. Annular lipids stabilize integral membrane proteins. Stabilization occurs through electrostatic and possibly other interactions between the lipid headgroups and the charged amino acid residues close to the phospholipid-water interface, and hydrophobic interactions between the fatty acyl chains and the membrane-spanning segments. Reconstitution techniques allow manipulation of the lipid composition of the membrane in a way that is difficult to achieve in vivo. The physical characteristics of membrane lipids that affect protein-mediated transport functions have been studied in liposomal systems that separate an inner and outer compartment. The activity of most transport proteins is modulated by the bulk physical characteristics of the lipid bilayer, while specific lipid requirements appear rare.
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Affiliation(s)
- G I Veld
- Department of Microbiology, University of Groningen, The Netherlands
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Riek R, Apell HJ. Investigation of reconstitution of the Na, K-ATPase in lipid vesicles. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1148:321-30. [PMID: 8389199 DOI: 10.1016/0005-2736(93)90146-q] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Vesicles containing Na,K-ATPase were prepared by a dialysis method in buffers with various concentrations of K+ and Na+ ions. Ion-exchange chromatography has been used to separate proteoliposomes into protein-depleted and protein-rich fractions. The pumping activity of reconstituted ion pumps has been determined in the different fractions of the vesicle preparation using voltage-dependent fluorescence dyes. This method allowed to characterise vesicle fractions by a quantity which is proportional to the average number of pumps per vesicle with an active (inside-out) orientation. It could be shown that both, the amount of enzymatic active protein and the orientation of Na,K-ATPase in the vesicle lipid bilayer, is partially controlled by the Na+ and K+ concentration in the buffer during vesicle formation. High Na+ concentrations preferentially maintain the E1 conformation of the enzyme, which is less stable against denaturation during the dialysis, but displays a higher percentage of inside-out orientation of the transport-active protein. High K+ concentrations maintain the E2 conformation of the enzyme, which is stable against denaturation during the dialysis, but leads to a random orientation of the pump during dialysis.
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Chapter 11 The (CA2+-Mg2+)-ATPase and other membrane proteins: what reconstitution tells us about the biological membrane. ACTA ACUST UNITED AC 1993. [DOI: 10.1016/s0167-7306(08)60240-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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18
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Clarke RJ, Schrimpf P, Schöneich M. Spectroscopic investigations of the potential-sensitive membrane probe RH421. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1112:142-52. [PMID: 1329964 DOI: 10.1016/0005-2736(92)90264-m] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The absorbance spectra, fluorescence emission and excitation spectra, and fluorescence anisotropy of the potential-sensitive styryl dye RH421 have been investigated in aqueous solution and bound to the lipid membrane. The potential-sensitive response of the dye has been studied using a preparation of membrane fragments containing a high density of Na+, K(+)-ATPase molecules. In aqueous solution the dye is sensitive both to changes in pH and ionic strength. Evidence has been found that the dye readily aggregates in aqueous solution. Aggregation is enhanced by an increase in ionic strength. The aggregates formed display a low fluorescence intensity. At high pH values (above approx. 8) changes in the dye's fluorescence spectra are observed, which may be due to a reaction of the dye with hydroxide ions. When bound to the membrane the dye also exhibits concentration-dependent fluorescence changes. The potential-sensitive response of the dye in Na(+),K(+)-ATPase membrane fragments after addition of MgATP in the presence of Na+ ions cannot be explained by a purely electrochromic mechanism. The results are consistent with either a potential-dependent equilibrium between membrane-bound dye monomers and membrane-bound dimers, similar to that previously proposed for the dye merocyanine 540, or with a field-induced structural change of the membrane.
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Affiliation(s)
- R J Clarke
- Fritz-Haber-Institut, Max-Planck-Gesellschaft, Berlin, Germany
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19
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Schuurmans Stekhoven FM, Tesser GI, Ramsteyn G, Swarts HG, De Pont JJ. Binding of ethylenediamine to phosphatidylserine is inhibitory to Na+/K(+)-ATPase. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1109:17-32. [PMID: 1324002 DOI: 10.1016/0005-2736(92)90182-l] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Covalent linkage of ethylenediamine with the Na+/K(+)-ATPase complex from rabbit kidney outer medulla by the use of the water-soluble carbodiimide, N-ethyl,N'-(3-dimethylaminopropyl)carbodiimide, resulted in a 73% reaction with phosphatidylserine and only 27% with carboxylic groups in the proteic component of the enzyme. Condensation products from the reaction between phosphatidylserine and ethylenediamine, N-(O-phosphatidylseryl)ethylenediamine, N,N'-bis(O-phosphatidylseryl)ethylenediamine and its intermediary product O-phosphatidyl-[N,N'-bis(seryl)]ethylenediamine, were synthesised. Symmetrically substituted ethylenediamine was the most likely condensation product of ethylenediamine with endogenous phosphatidylserine. The synthesised lipids were incorporated in proteoliposomes containing Na+/K(+)-ATPase and only the addition of the phospholipid phosphatidylcholine. The ratio of phospholipid to protein was 52 (w/w). These proteoliposomes were perforated by the addition of 0.5% cholate and both the Na(+)-dependent phosphorylation level and its dependence on Na+, Mg2+ and ATP were measured. Phosphatidylcholine alone increased the half-maximal activation concentration for Na+ ([Na+]0.5) from 0.2 to 1-2 mM, for Mg2+ from 0.1 to 0.8 microM and for ATP from 0.02 to 0.3 microM. The Ki for K+ (in the absence of Na+) was unaffected: 12.8 microM vs. 12.5 microM in the non-reconstituted system. Replacing 10 mol% of phosphatidylcholine by phosphatidylethanolamine: or phosphatidylserine had no significant effect on [Na+]0.5: 1.1 and 0.7 mM, respectively. Replacing 5 mol% phosphatidylcholine by the bis(phosphatidylseryl) substituent of ethylenediamine further increased [Na+]0.5 to 13.7 mM, while half-maximal activation concentrations for Mg2+ and ATP were unaltered. The mono-phosphatidylseryl derivatives of ethylenediamine, each 5 mol%, also increased [Na+]0.5, but to a lesser extent (3.2-3.8 mM). In addition to their competitive effects, the phosphatidylseryl-substituted ethylenediamine compounds exerted a slowly-increasing non-competitive inhibition, not only in phosphorylation, but also in overall ATPase activity, which was reduced, although not abolished, by exogenous protein (bovine serum albumin). A detergent-like action in the usual sense is unlikely since liposomes containing these lipids remained intact. These studies prove that phospholipids are not only required for optimal activity of this transport enzyme, but in excess or in compositions deviating from the normal, may also be inhibitory.
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In 't Veld G, Driessen AJ, Konings WN. Effect of the unsaturation of phospholipid acyl chains on leucine transport of Lactococcus lactis and membrane permeability. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1108:31-9. [PMID: 1643079 DOI: 10.1016/0005-2736(92)90111-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The effect of the degree of unsaturation of the phospholipid acyl chains on the branched-chain amino acid transport system of Lactococcus lactis was investigated by the use of a membrane fusion technique. Transport activity was analyzed in hybrid membranes composed of equimolar mixtures of synthetic unsaturated phosphatidylethanolamine (PE) and phosphatidylcholine (PC) in which the number of cis double bonds in the 18-carbon acyl chains was varied. The accumulation level and initial rate of both counterflow and protonmotive-force driven transport of leucine decreased with increasing number of double bonds. The reduction in transport activity with increasing number of double bonds correlated with an increase in the passive permeability of the membranes to leucine. The membrane fluidity was hardly affected by the double bond content. It is concluded that the degree of lipid acyl chain unsaturation is a minor determinant of the activity of the branched chain amino acid transport system, but effects strongly the passive permeability of the membrane.
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Affiliation(s)
- G In 't Veld
- Department of Microbiology, University of Groningen, Haren, Netherlands
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21
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Marín R, Rodríguez AJ, Proverbio T. Partial characterization of the inhibitory effect of lipid peroxidation on the ouabain-insensitive Na-ATPase of rat kidney cortex plasma membranes. J Bioenerg Biomembr 1992; 24:329-35. [PMID: 1400277 DOI: 10.1007/bf00768853] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The present work evaluates the effect of lipid peroxidation on the ouabain-insensitive Na-ATPase of basolateral plasma membranes from rat kidney proximal tubular cells as an indirect way to study the lipid dependence of this enzyme. An inverse relationship between lipid peroxidation and Na-ATPase activity was found. This effect was due neither to a change in the optimal Km of the system for Na+ nor for the substrate Mg:ATP, nor the optimal pH value of the medium. The optimal temperature value, however, was shifted toward a higher value. There was also an increase of the apparent energy of activation in the region of temperatures above the transition point (20 degrees C) with increase in lipid peroxidation. Peroxidized membranes incubated with phosphatidylcholine from soybean restored their Na-ATPase activity. On the other hand, the Na-ATPase activity was sensitive to oleoly lysophosphatidylcholine. These results suggest that lipid peroxidation might be affecting the Na-ATPase activity through either an increase of peroxidized phospholipids, which might change the membrane fluidity of the lipid microenvironment of the ATPase molecules, or through a direct effect of lysophospholipids released during the lipid peroxidation.
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Affiliation(s)
- R Marín
- Centro de Biofísica y Bioquímica (CBB), Instituto Venezolano de Investigaciones Científicas (IVIC), Caracas
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22
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Michelangeli F, Munkonge FM. Methods of reconstitution of the purified sarcoplasmic reticulum (Ca(2+)-Mg2+)-ATPase using bile salt detergents to form membranes of defined lipid to protein ratios or sealed vesicles. Anal Biochem 1991; 194:231-6. [PMID: 1830725 DOI: 10.1016/0003-2697(91)90223-g] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
A detailed methodology is presented of two reconstitution protocols for the (Ca(2+)-Mg2+)-ATPase from rabbit skeletal muscle, using the detergent potassium cholate. Method A was shown to produce fully fragmented membranes of definable lipid to protein ratios, which were unable to take up calcium upon hydrolysis of ATP. This protocol was shown to produce a homologous population of membranes with respect to their lipid and protein composition at lipid to protein ratios up to 900:1 (mol/mol). Method B produced vesicles only of high lipid to protein ratios (3000:1), which have the ability to accumulate calcium on addition of ATP. Calcium accumulation and ATP hydrolysis for the ATPase reconstituted into different fatty acyl chain length phospholipids were also studied.
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Affiliation(s)
- F Michelangeli
- Istituto di Patologia Generale, Università di Padova, Italy
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23
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Cornelius F. Functional reconstitution of the sodium pump. Kinetics of exchange reactions performed by reconstituted Na/K-ATPase. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1071:19-66. [PMID: 1848452 DOI: 10.1016/0304-4157(91)90011-k] [Citation(s) in RCA: 102] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- F Cornelius
- Institute of Biophysics, University of Aarhus, Denmark
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24
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Clarke RJ. Binding and diffusion kinetics of the interaction of a hydrophobic potential-sensitive dye with lipid vesicles. Biophys Chem 1991; 39:91-106. [PMID: 2012838 DOI: 10.1016/0301-4622(91)85010-n] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The interaction of the dye oxonol V with unilamellar dioleoylphosphatidylcholine vesicles has previously been investigated using a fluorescence stopped-flow technique. It has been found that the most suitable mathematical description of the equilibrium and kinetic data is obtained by assuming the presence of saturable dye binding sites in both monolayers of the vesicle membrane and a potential-dependent diffusion across the membrane interior between these two classes of sites. A kinetic model is presented which takes into account the degree of saturation of the binding sites, the degree of fluorescence quenching within the membrane, and the production of an electrical potential gradient across the membrane interior by the binding of the negatively charged dye. The model successfully predicts the time course of the fluorescence change due to binding and diffusion over the complete range of dye and vesicle concentrations as well as the fluorescence response of the dye to changing membrane potential.
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Affiliation(s)
- R J Clarke
- School of Chemical Sciences, University of East Anglia, Norwich, U.K
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25
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Apell HJ, Solioz M. Electrogenic transport by the Enterococcus hirae ATPase. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1017:221-8. [PMID: 2164846 DOI: 10.1016/0005-2728(90)90188-a] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A transport ATPase from Enterococcus hirae was reconstituted in lipid vesicles and its electrogenic action investigated with the fluorescent dye oxonol VI as membrane potential probe. Reconstitution in bacterial and in soybean phospholipid mixtures led to transport-active vesicle preparations. Inside-out oriented ATPase molecules were activated by the addition of ATP to the extravesicular medium, generating in all experiments an intravesicularly positive potential. The extravesicular pH strongly influenced the initial pumping rate and the duration of the pumping activity. At neutral pH, transient pumping activity was observed, lasting for 1-2 min, while at pH 5.6, pumping was continuous. The transport activity was not dependent on the ionic composition of the buffer on either side of the membrane. These findings can be interpreted as the action of a proton ATPase, regulated by the cytoplasmic proton concentration and electrogenically translocating protons from the cytoplasm to the extracellular space.
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Affiliation(s)
- H J Apell
- Department of Biology, University of Konstanz, F.R.G
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26
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Villalobo A. Reconstitution of ion-motive transport ATPases in artificial lipid membranes. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1017:1-48. [PMID: 1693288 DOI: 10.1016/0005-2728(90)90176-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- A Villalobo
- Instituto de Investigaciones Biomédicas, C.S.I.C., Madrid, Spain
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27
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28
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Tanaka Y, Ando S. Synaptic aging as revealed by changes in membrane potential and decreased activity of Na+,K(+)-ATPase. Brain Res 1990; 506:46-52. [PMID: 2154278 DOI: 10.1016/0006-8993(90)91197-o] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Age-related changes in the membrane potential of nerve terminals were investigated by monitoring the accumulation of tritium-labeled triphenylmethylphosphonium ion, [3H]TPMP+, in mouse cortical synaptosomes. The resting membrane potential became less negative with advancing age, that is, it changed from -64.5 +/- 0.8 to -58.1 +/- 2.3 mV between 6 and 27 months of age. The intrasynaptosomal potassium concentration was found to decrease concomitantly by 13% in aged mice (56.6 +/- 0.9 mM) as compared to young-adult mice (64.9 +/- 0.5 mM). The ouabain-sensitive Na+,K(+)-ATPase activity of synaptic plasma membranes decreased in late senescence to 82% of the adult level. To examine the correlation with the decreased Na+,K(+)-ATPase activity, the membrane lipid composition was analyzed. Among the membrane phospholipids, only the content of phosphatidylcholine decreased in the course of senescence. The changes in the Na+,K(+)-ATPase activity were found to be positively correlated with the changes in the phospholipid content, and more specifically with the changes in the phosphatidyl-choline content. These results suggest that age-related alterations in the microenvironment constructed by phospholipids may decrease the activity of Na+,K+-ATPase, resulting in neuronal ion imbalance and decreased membrane potential. This might be responsible in part for altered functions of nerve terminals in aging brain.
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Affiliation(s)
- Y Tanaka
- Department of Biochemistry, Tokyo Metropolitan Institute of Gerontology, Japan
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29
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Tozzi-Ciancarelli MG, Di Giulio A, Troiani-Sevi E, D'Alfonso A, Amicosante G, Oratore A. Human erythrocyte damage at the initial stages of oxidative stress. CELL BIOPHYSICS 1989; 15:225-34. [PMID: 2480182 DOI: 10.1007/bf02989685] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Specific fluorescent probes have been used to monitor changes in erythrocyte membranes in the first stages of the hemolytic process induced by irradiation with visible light in the presence of protoporphyrin IX. Although no change, or even a slight increase of fluorescence anisotropy, occurred with two probes having a preferential binding to membrane proteins, such as fluorescamine and 3-pyrene maleimide, the fluorescence anisotropy of two lipophilic probes, namely diphenyl-hexatriene and anilino-naphthalene sulfonate, underwent a substantial decrease upon irradiation. Concomitantly, a dramatic decrease of ATPase activity and an increase of thiobarbituric-reacting substances were observed in erythrocyte membranes. Instead, there was no effect on the activities of the intracellular enzymes glucose-6-phosphate dehydrogenase and pyruvate kinase. These findings are consistent with the hypothesis that protoporphyrin-sensitized irradiation induces, primarily in the erythrocyte membrane, the peroxidation of the lipid component, which results in an increase of the fluidity of the bilayer. Hemolysis eventually occurs because of an osmotic imbalance resulting from the combination of increased passive diffusion and decreased active ion transport.
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Affiliation(s)
- M G Tozzi-Ciancarelli
- Dipartimento di Scienze e Tecnologie Biomediche e Biometria, Facoltà di Medicina, Università dell'Aquila, Italy
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30
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Clarke RJ, Apell HJ. A stopped-flow kinetic study of the interaction of potential-sensitive oxonol dyes with lipid vesicles. Biophys Chem 1989; 34:225-37. [PMID: 2611347 DOI: 10.1016/0301-4622(89)80061-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The interaction of the dyes oxonol V and oxonol VI with unilamellar dioleoylphosphatidylcholine vesicles was investigated using a fluorescence stopped-flow technique. On mixing with the vesicles, both dyes exhibit an increase in their fluorescence, which occurs in two phases. According to the dependence of the reciprocal relaxation time on vesicle concentration, the rapid phase appears to be due to a second-order binding of the dye to the lipid membrane, which is very close to being diffusion-controlled. The slow phase is almost independent of vesicle concentration, and it is suggested that this may be due to a change in dye conformation or position within the membrane, possibly diffusion across the membrane to the internal monolayer. The response times of the dyes to a rapid jump in the membrane potential has also been investigated. Oxonol VI was found to respond to the potential change in less than 1 s, whereas oxonol required several minutes. This has been attributed to lower mobility of oxonol V within the lipid membrane.
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Affiliation(s)
- R J Clarke
- Department of Biology, University of Konstanz, F.R.G
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31
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Clarke RJ, Apell HJ, Läuger P. Pump current and Na+/K+ coupling ratio of Na+/K+-ATPase in reconstituted lipid vesicles. BIOCHIMICA ET BIOPHYSICA ACTA 1989; 981:326-36. [PMID: 2543461 DOI: 10.1016/0005-2736(89)90044-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A method is described for studying the coupling ratio of the Na+/K+ pump, i.e., the ratio of pump-mediated fluxes of Na+ and K+, in a reconstituted system. The method is based on the comparison of the pump-generated current with the rate of K+ transport. Na+/K+-ATPase from kidney is incorporated into the membrane of artificial lipid vesicles; ATPase molecules with outward-oriented ATP-binding site are activated by addition of ATP to the medium. Using oxonol VI as a potential-sensitive dye for measuring transmembrane voltage, the pump current is determined from the change of voltage with time t. In a second set of experiments, the membrane is made selectively K+-permeable by addition of valinomycin, so that the membrane voltage U is equal to the Nernst potential of K+. Under this condition, dU/dt reflects the change of intravesicular K+ concentration and thus the flux of K+. Values of the Na+/K+ coupling ratio determined in this way are close to 1.5 in the experimental range (10-75 mM) of extravesicular (cytoplasmic) Na+ concentrations.
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Affiliation(s)
- R J Clarke
- Department of Biology, University of Konstanz, F.R.G
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32
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Uratani Y, Wakayama N, Hoshino T. Effect of lipid acyl chain length on activity of sodium-dependent leucine transport system in Pseudomonas aeruginosa. J Biol Chem 1987. [DOI: 10.1016/s0021-9258(18)45470-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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33
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Apell HJ, Bersch B. Oxonol VI as an optical indicator for membrane potentials in lipid vesicles. BIOCHIMICA ET BIOPHYSICA ACTA 1987; 903:480-94. [PMID: 2444259 DOI: 10.1016/0005-2736(87)90055-1] [Citation(s) in RCA: 129] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Experiments with large unilamellar dioleoylphosphatidylcholine vesicles were carried out in order to study the effect of membrane potential on the fluorescence of Oxonol VI. A partition equilibrium of dye between membrane and water was found to exist with a partition coefficient gamma identical to c lipid/c water of about 19,000 (at zero voltage). In the presence of an inside-positive membrane potential, the negatively charged dye accumulates in the intravesicular aqueous space according to a Nernst equilibrium. This leads to an increased adsorption of dye to the inner lipid monolayer and to a concomitant increase of fluorescence. The fluorescence change can be calibrated as a function of transmembrane voltage by generating a potassium diffusion potential in the presence of valinomycin. The intrinsic fluorescence of the membrane-bound dye is not affected by voltage; the whole influence of voltage on the fluorescence results from voltage-dependent partitioning of the dye between water and membrane. The voltage dependence of the apparent partition coefficient can be quantitatively described by a three-capacitor model in which the dye is assumed to bind to adsorption planes located on the hydrocarbon side of the membrane/solution interface. Oxonol VI was found to be suitable for detecting changes of membrane potential associated with the activity of the (Na+ + K+)-ATPase in reconstituted vesicles. When ATP is added to the external medium, pump molecules with the ATP-binding side facing outward become activated; this results in a translocation of net positive charge towards the vesicle interior. Under this condition, fluorescence changes corresponding to (inside-positive) potentials of up to 150-200 mV are observed. After the build-up of the membrane potential, a quasi-stationary state is reached in which the pump current is compensated by a back-flow of charge through passive conductance pathways.
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Affiliation(s)
- H J Apell
- Department of Biology, University of Konstanz, F.R.G
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34
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Apell HJ, Marcus MM. (Na+ + K+)-ATPase in artificial lipid vesicles: influence of the concentration of mono- and divalent cations on the pumping rate. BIOCHIMICA ET BIOPHYSICA ACTA 1986; 862:254-64. [PMID: 3022809 DOI: 10.1016/0005-2736(86)90226-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
(Na+ + K+)-ATPase from kidney outer medulla was incorporated into artificial dioleoylphosphatidylcholine vesicles. Transport activity was induced by adding ATP to the external medium. A voltage-sensitive dye was used to detect the ATP-driven potassium extrusion in the presence of valinomycin. The observed substrate-protein interactions of the reconstituted (Na+ + K+)-ATPase largely agree with that from native tissues. An agreement between ATP hydrolysis and transport activity is given for concentration dependences of sodium, potassium, magnesium and calcium ions. The only significant deviations were observed in the influence of pH. Protons were found to have different influence on transport, enzymatic activity and phosphorylation of the enzyme. The transport studies showed a twofold interaction of protons with the protein: competition with sodium at the cytoplasmic ion binding sites, a non competitive inhibition of transport which is not correlated with protein phosphorylation.
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35
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Apell HJ, Nelson MT, Marcus MM, Läuger P. Effects of the ATP, ADP and inorganic phosphate on the transport rate of the Na+,K+-pump. BIOCHIMICA ET BIOPHYSICA ACTA 1986; 857:105-15. [PMID: 3008841 DOI: 10.1016/0005-2736(86)90103-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
(Na+ + K+)-ATPase from kidney outer medulla was incorporated into artificial dioleoylphosphatidylcholine vesicles. In the reconstituted system the pump can be activated by adding ATP to the external medium. ATP-driven potassium extrusion by the Na+,K+-pump was studied using a voltage-sensitive dye in the presence of valinomycin. ADP strongly reduced the turnover rate of the pump with a concentration for half-maximal inhibition of cD,1/2 = 0.1 mM. cD,1/2 was found to be virtually independent of ATP concentration, indicating that the inhibition is non-competitive with respect to ATP. The non-competitive inhibition by ADP can be explained on the basis of the Post-Albers reaction cycle of the Na+,K+-pump, assuming that the main action of ADP is the reversal of the phosphorylation step. A similar 'product inhibition' was observed with inorganic phosphate, but at much higher concentrations (cP,1/2 = 14 mM).
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36
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Apell HJ, Läuger P. Quantitative analysis of pump-mediated fluxes in reconstituted lipid vesicles. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 1986. [DOI: 10.1016/0005-2736(86)90432-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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