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Jiao X, Huang W, Wang A, Wu B, Kang Q, Luo X, Bai L, Deng Z. Crystallographic Deciphering of Spontaneous Self-Assembly of Achiral Calciphores to Chiral Complexes. Chemistry 2023; 29:e202203127. [PMID: 36408990 DOI: 10.1002/chem.202203127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Revised: 11/17/2022] [Accepted: 11/21/2022] [Indexed: 11/23/2022]
Abstract
Thiapyricins (TPC-A/B, 1 and 2), which are new metallophore scaffolds exhibiting selective divalent cation binding property, were produced in response to metal-deprived conditions by Saccharothrix sp. TRM_47004 isolated from the Lop Nor Salt Lake. TPCs represent a thiazolyl-pyridine skeleton of a calcium-binding natural product, calciphore, owing to the selectivity to calcium ions among diverse metal ions. The thiapyricins exhibited notable co-crystalline characteristics of the apo- and holo-forms with racemic enantiomers comprising a pair of space isomers in a Δ/Λ-form. Therefore, we postulated a mechanism for the four-hierarchical self-assembly of achiral natural products into chiral complexes. Furthermore, their metal-chelating trait aided the adaptation of the host during metal starvation by increasing the production of TPCs. This study presents a structural paradigm of a new calciphore, provides insight into the mechanism of natural product assembly, and highlights the causality between the production of the metallophore and metallic habitats.
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Affiliation(s)
- Xingzhi Jiao
- State Key Laboratory of, Microbial Metabolism, Shanghai-Islamabad-Belgrade Joint Innovation Center on Antibacterial Resistances, Joint International Research, Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, P. R. China
| | - Wei Huang
- College of Life Science, Tarim University, 843300, Alar, Xinjiang, P. R. China
| | - Anqi Wang
- State Key Laboratory of, Microbial Metabolism, Shanghai-Islamabad-Belgrade Joint Innovation Center on Antibacterial Resistances, Joint International Research, Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, P. R. China
| | - Banghao Wu
- State Key Laboratory of, Microbial Metabolism, Shanghai-Islamabad-Belgrade Joint Innovation Center on Antibacterial Resistances, Joint International Research, Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, P. R. China
| | - Qianjin Kang
- State Key Laboratory of, Microbial Metabolism, Shanghai-Islamabad-Belgrade Joint Innovation Center on Antibacterial Resistances, Joint International Research, Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, P. R. China
| | - Xiaoxia Luo
- College of Life Science, Tarim University, 843300, Alar, Xinjiang, P. R. China
| | - Linquan Bai
- State Key Laboratory of, Microbial Metabolism, Shanghai-Islamabad-Belgrade Joint Innovation Center on Antibacterial Resistances, Joint International Research, Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, P. R. China.,College of Life Science, Tarim University, 843300, Alar, Xinjiang, P. R. China
| | - Zixin Deng
- State Key Laboratory of, Microbial Metabolism, Shanghai-Islamabad-Belgrade Joint Innovation Center on Antibacterial Resistances, Joint International Research, Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 200240, Shanghai, P. R. China
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Chelombitko MA, Firsov AM, Kotova EA, Rokitskaya TI, Khailova LS, Popova LB, Chernyak BV, Antonenko YN. Usnic acid as calcium ionophore and mast cells stimulator. Biochimica et Biophysica Acta (BBA) - Biomembranes 2020; 1862:183303. [DOI: 10.1016/j.bbamem.2020.183303] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 03/14/2020] [Accepted: 03/31/2020] [Indexed: 01/09/2023]
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Yang DM, Manurung RV, Lin YS, Chiu TY, Lai WQ, Chang YF, Fu TF. Monitoring the Heavy Metal Lead Inside Living Drosophila with a FRET-Based Biosensor. Sensors (Basel) 2020; 20:E1712. [PMID: 32204388 PMCID: PMC7146181 DOI: 10.3390/s20061712] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 03/16/2020] [Accepted: 03/18/2020] [Indexed: 01/06/2023]
Abstract
The harmful impact of the heavy metal lead on human health has been known for years. However, materials that contain lead remain in the environment. Measuring the blood lead level (BLL) is the only way to officially evaluate the degree of exposure to lead. The so-called "safe value" of the BLL seems to unreliably represent the secure threshold for children. In general, lead's underlying toxicological mechanism remains unclear and needs to be elucidated. Therefore, we developed a novel genetically encoded fluorescence resonance energy transfer (FRET)-based lead biosensor, Met-lead, and applied it to transgenic Drosophila to perform further investigations. We combined Met-lead with the UAS-GAL4 system to the sensor protein specifically expressed within certain regions of fly brains. Using a suitable imaging platform, including a fast epifluorescent or confocal laser-scanning/two-photon microscope with high resolution, we recorded the changes in lead content inside fly brains ex vivo and in vivo and at different life stages. The blood-brain barrier was found to play an important role in the protection of neurons in the brain against damage due to the heavy metal lead, either through food or microinjection into the abdomen. Met-lead has the potential to be a powerful tool for the sensing of lead within living organisms by employing either a fast epi-FRET microscope or high-resolution brain imaging.
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Affiliation(s)
- De-Ming Yang
- Microscopy Service Laboratory, Basic Research Division, Department of Medical Research, Taipei Veterans General Hospital, Taipei 11217, Taiwan;
- Institute of Biophotonics, School of Medical Technology & Engineering, National Yang-Ming University, Taipei 11221, Taiwan; (Y.-S.L.); (T.-Y.C.)
- Biophotonics and Molecular Imaging Research Center (BMIRC), National Yang-Ming University, Taipei 112, Taiwan
| | - Robeth Viktoria Manurung
- Research Center for Electronics and Telecommunication, Indonesian Institute of Sciences (LIPI), Bandung 40135, Indonesia;
| | - Yu-Syuan Lin
- Institute of Biophotonics, School of Medical Technology & Engineering, National Yang-Ming University, Taipei 11221, Taiwan; (Y.-S.L.); (T.-Y.C.)
| | - Tai-Yu Chiu
- Institute of Biophotonics, School of Medical Technology & Engineering, National Yang-Ming University, Taipei 11221, Taiwan; (Y.-S.L.); (T.-Y.C.)
| | - Wei-Qun Lai
- Microscopy Service Laboratory, Basic Research Division, Department of Medical Research, Taipei Veterans General Hospital, Taipei 11217, Taiwan;
- Institute of Biophotonics, School of Medical Technology & Engineering, National Yang-Ming University, Taipei 11221, Taiwan; (Y.-S.L.); (T.-Y.C.)
| | - Yu-Fen Chang
- LumiSTAR Biotechnology, Inc., Taipei City 115, Taiwan;
| | - Tsai-Feng Fu
- Department of Applied Chemistry, National Chi-Nan University, Nantou 54561, Taiwan;
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Garni M, Thamboo S, Schoenenberger CA, Palivan CG. Biopores/membrane proteins in synthetic polymer membranes. Biochim Biophys Acta Biomembr 2016; 1859:619-638. [PMID: 27984019 DOI: 10.1016/j.bbamem.2016.10.015] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Revised: 10/20/2016] [Accepted: 10/25/2016] [Indexed: 12/14/2022]
Abstract
BACKGROUND Mimicking cell membranes by simple models based on the reconstitution of membrane proteins in lipid bilayers represents a straightforward approach to understand biological function of these proteins. This biomimetic strategy has been extended to synthetic membranes that have advantages in terms of chemical and mechanical stability, thus providing more robust hybrid membranes. SCOPE OF THE REVIEW We present here how membrane proteins and biopores have been inserted both in the membrane of nanosized and microsized compartments, and in planar membranes under various conditions. Such bio-hybrid membranes have new properties (as for example, permeability to ions/molecules), and functionality depending on the specificity of the inserted biomolecules. Interestingly, membrane proteins can be functionally inserted in synthetic membranes provided these have appropriate properties to overcome the high hydrophobic mismatch between the size of the biomolecule and the membrane thickness. MAJOR CONCLUSION Functional insertion of membrane proteins and biopores in synthetic membranes of compartments or in planar membranes is possible by an appropriate selection of the amphiphilic copolymers, and conditions of the self-assembly process. These hybrid membranes have new properties and functionality based on the specificity of the biomolecules and the nature of the synthetic membranes. GENERAL SIGNIFICANCE Bio-hybrid membranes represent new solutions for the development of nanoreactors, artificial organelles or active surfaces/membranes that, by further gaining in complexity and functionality, will promote translational applications. This article is part of a Special Issue entitled: Lipid order/lipid defects and lipid-control of protein activity edited by Dirk Schneider.
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Affiliation(s)
- Martina Garni
- Chemistry Department, University of Basel, Klingelbergstrasse 80, Switzerland
| | - Sagana Thamboo
- Chemistry Department, University of Basel, Klingelbergstrasse 80, Switzerland
| | | | - Cornelia G Palivan
- Chemistry Department, University of Basel, Klingelbergstrasse 80, Switzerland.
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Raatschen N, Wenzel M, Ole Leichert LI, Düchting P, Krämer U, Bandow JE. Extracting iron and manganese from bacteria with ionophores - a mechanism against competitors characterized by increased potency in environments low in micronutrients. Proteomics 2013; 13:1358-70. [PMID: 23412951 DOI: 10.1002/pmic.201200556] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Revised: 01/24/2013] [Accepted: 01/31/2013] [Indexed: 11/10/2022]
Abstract
To maintain their metal ion homeostasis, bacteria critically depend on membrane integrity and controlled ion translocation. Terrestrial Streptomyces species undermine the function of the cytoplasmic membrane as diffusion barrier for metal cations in competitors using ionophores. Although the properties of the divalent cation ionophores calcimycin and ionomycin have been characterized to some extent in vitro, their effects on bacterial ion homeostasis, the factors leading to bacterial cell death, and their ecological role are poorly understood. To gain insight into their antibacterial mechanism, we determined the metal ion composition of the soil bacterium Bacillus subtilis after treatment with calcimycin and ionomycin. Within 15 min the cells lost approximately half of their cellular iron and manganese content whereas calcium levels increased. The proteomic response of B. subtilis provided evidence that disturbance of metal cation homeostasis is accompanied by intracellular oxidative stress, which was confirmed with a ROS-specific fluorescent probe. B. subtilis showed enhanced sensitivity to the ionophores in medium lacking iron or manganese. Furthermore, in the presence of ionophores bacteria were sensitive to high calcium levels. These findings suggest that divalent cation ionophores are particularly effective against competing microorganisms in soils rich in available calcium and low in available iron and manganese.
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Affiliation(s)
- Nadja Raatschen
- Biology of Microorganisms, Ruhr University Bochum, Bochum, Germany
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Ivanova J, Pantcheva IN, Mitewa M, Simova S, Tanabe M, Osakada K. Cd(II) and Pb(II) complexes of the polyether ionophorous antibiotic salinomycin. Chem Cent J 2011; 5:52. [PMID: 21906282 PMCID: PMC3184049 DOI: 10.1186/1752-153x-5-52] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Accepted: 09/09/2011] [Indexed: 12/13/2022] Open
Abstract
Background The natural polyether ionophorous antibiotics are used for the treatment of coccidiosis in poultry and ruminants. They are effective agents against infections caused by Gram-positive microorganisms. On the other hand, it was found that some of these compounds selectively bind lead(II) ions in in vivo experiments, despite so far no Pb(II)-containing compounds of defined composition have been isolated and characterized. To assess the potential of polyether ionophores as possible antidotes in the agriculture, a detailed study on their in vitro complexation with toxic metal ions is required. In the present paper we report for the first time the preparation and the structure elucidation of salinomycin complexes with ions of cadmium(II) and lead(II). Results New metal(II) complexes of the polyether ionophorous antibiotic salinomycin with Cd(II) and Pb(II) ions were prepared and structurally characterized by IR, FAB-MS and NMR techniques. The spectroscopic information and elemental analysis data reveal that sodium salinomycin (SalNa) undergoes a reaction with heavy metal(II) ions to form [Cd(Sal)2(H2O)2] (1) and [Pb(Sal)(NO3)] (2), respectively. Abstraction of sodium ions from the cavity of the antibiotic is occurring during the complexation reaction. Salinomycin coordinates with cadmium(II) ions as a bidentate monoanionic ligand through the deprotonated carboxylic moiety and one of the hydroxyl groups to yield 1. Two salinomycin anions occupy the equatorial plane of the Cd(II) center, while two water molecules take the axial positions of the inner coordination sphere of the metal(II) cation. Complex 2 consists of monoanionic salinomycin acting in polydentate coordination mode in a molar ratio of 1: 1 to the metal ion with one nitrate ion for charge compensation. Conclusion The formation of the salinomycin heavy metal(II) complexes indicates a possible antidote activity of the ligand in case of chronic/acute intoxications likely to occur in the stock farming.
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Affiliation(s)
- Juliana Ivanova
- Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Acad, G, Bontchev Str,, build, 9, 1113 Sofia, Bulgaria.
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Pantcheva IN, Ivanova J, Zhorova R, Mitewa M, Simova S, Mayer-Figge H, Sheldrick WS. Nickel(II) and zinc(II) dimonensinates: Single crystal X-ray structure, spectral properties and bactericidal activity. Inorganica Chim Acta 2010. [DOI: 10.1016/j.ica.2010.02.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Sakanashi Y, Oyama TM, Matsuo Y, Oyama TB, Nishimura Y, Ishida S, Imai S, Okano Y, Oyama Y. Zn2+, derived from cell preparation, partly attenuates Ca2+-dependent cell death induced by A23187, calcium ionophore, in rat thymocytes. Toxicol In Vitro 2009; 23:338-45. [DOI: 10.1016/j.tiv.2008.12.006] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2008] [Revised: 11/05/2008] [Accepted: 12/05/2008] [Indexed: 11/22/2022]
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Dorkov P, Pantcheva IN, Sheldrick WS, Mayer-Figge H, Petrova R, Mitewa M. Synthesis, structure and antimicrobial activity of manganese(II) and cobalt(II) complexes of the polyether ionophore antibiotic Sodium Monensin A. J Inorg Biochem 2008; 102:26-32. [PMID: 17692921 DOI: 10.1016/j.jinorgbio.2007.06.033] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2007] [Revised: 06/20/2007] [Accepted: 06/25/2007] [Indexed: 11/16/2022]
Abstract
Mononuclear neutral manganese(II) and cobalt(II) complexes with the antibiotic Sodium Monensin A (Mon-Na, 1b) were synthesized and characterized. The crystal structures of M(Mon-Na)2Cl2.H2O (M=Mn, 2; M=Co, 3) were determined by X-ray crystallography. The complexes crystallize in monoclinic space group C2 with a tetrahedrally coordinated transition metal attached to oxygen atoms of deprotonated carboxyl groups of two Sodium Monensin molecules and two chloride ions. The sodium ion remains in the cavity of the ligand and cannot be replaced by Mn(II) or Co(II). The complexes were additionally characterized by different spectroscopic techniques (UV-Visible, EPR, FAB-MS). A preferable octahedral environment around the transition metal centers is observed in polar solvents while the complexes retain their tetrahedral structure in non-polar media. The antimicrobial activity of 1b, 2 and 3 was tested against Gram(+) and Gram(-) bacteria.
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Affiliation(s)
- Petar Dorkov
- Department of Analytical Chemistry, Faculty of Chemistry, Sofia University, 1, J. Bourchier Blvd., 1164 Sofia, Bulgaria
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Steinbaugh GE, Taylor RW, Pfeiffer DR. Oral Administration versus Intra-peritoneal Injection of Pb Affects Its Concentration in Selected Rat Tissues. INORG CHEM COMMUN 2007; 10:1371-1374. [PMID: 18438450 PMCID: PMC2344131 DOI: 10.1016/j.inoche.2007.08.024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
- Gregory E. Steinbaugh
- Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, Ohio 43210
| | - Richard W. Taylor
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019
| | - Douglas R. Pfeiffer
- Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, Ohio 43210
- Department of Internal Medicine, The Ohio State University, Columbus, Ohio 43210
- Institute for Mitochondrial Biology, The Ohio State University, Columbus, Ohio 43210
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Affiliation(s)
- R Aeryn Mayer
- Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
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Hamidinia SA, Erdahl WL, Chapman CJ, Steinbaugh GE, Taylor RW, Pfeiffer DR. Monensin improves the effectiveness of meso-dimercaptosuccinate when used to treat lead intoxication in rats. Environ Health Perspect 2006; 114:484-93. [PMID: 16581534 PMCID: PMC1440769 DOI: 10.1289/ehp.8279] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Among divalent cations, the ionophore monensin shows high activity and selectivity for the transport of lead ions (Pb2+) across phospholipid membranes. When coadministered to rats that were receiving meso-dimercaptosuccinate for treatment of Pb intoxication, monensin significantly increased the amount of Pb removed from femur, brain, and heart. It showed a tendency to increase Pb removal from liver and kidney but had no effect of this type in skeletal muscle. Tissue levels of several physiologic (calcium, cobalt, copper, iron, magnesium, manganese, molybdenum, zinc) and nonphysiologic (arsenic, cadmium, chromium, nickel, strontium) elements were also determined after the application of these compounds. Among the physiologic elements, a number of significant changes were seen, including both rising and falling values. The size of these changes was typically around 20% compared with control values, with the largest examples seen in femur. These changes often tended to reverse those of similar size that had occurred during Pb administration. Among the nonphysiologic elements, which were present in trace amounts, the changes were smaller in number but larger in size. None of these changes appears likely to be significant in terms of toxicity, and there were no signs of overt toxicity under any of the conditions employed. Monensin may act by cotransporting Pb2+ and OH- ions out of cells, in exchange for external sodium ions. The net effect would be to shuttle intracellular Pb2+ to extracellular dimercaptosuccinic acid thereby enhancing its effectiveness. Thus, monensin may be useful for the treatment of Pb intoxication when applied in combination with hydrophilic Pb2+ chelators.
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Affiliation(s)
- Shawn A Hamidinia
- Departments of Molecular and Cellular Biochemistry, Ohio State University, Columbus, Ohio, USA
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Hamidinia SA, Tan B, Erdahl WL, Chapman CJ, Taylor RW, Pfeiffer DR. The Ionophore Nigericin Transports Pb2+ with High Activity and Selectivity: A Comparison to Monensin and Ionomycin. Biochemistry 2004; 43:15956-65. [PMID: 15595852 DOI: 10.1021/bi048175z] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The K(+) ionophore nigericin is shown to be highly effective as an ionophore for Pb(2+) but not other divalent cations, including Cu(2+), Zn(2+), Cd(2+), Mn(2+), Co(2+), Ca(2+), Ni(2+), and Sr(2+). Among this group a minor activity for Cu(2+) transport is seen, while for the others activity is near or below the limit of detection. The selectivity of nigericin for Pb(2+) exceeds that of ionomycin or monensin and arises, at least in part, from a high stability of nigericin-Pb(2+) complexes. Plots of log rate vs log Pb(2+) or log ionophore concentration, together with the pH dependency, indicate that nigericin transports Pb(2+) via the species NigPbOH and by a mechanism that is predominately electroneutral. As with monensin and ionomycin, a minor fraction of activity may be electrogenic, based upon a stimulation of rate that is produced by agents which prevent the formation of transmembrane electrical potentials. Nigericin-catalyzed Pb(2+) transport is not inhibited by physiological concentrations of Ca(2+) or Mg(2+) and is only modestly affected by K(+) and Na(+) concentrations in the range of 0-100 mM. These characteristics, together with higher selectivity and efficiency, suggest that nigericin may be more useful than monensin in the treatment of Pb intoxication.
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Affiliation(s)
- Shawn A Hamidinia
- Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA
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Vest RS, Gonzales LJ, Permann SA, Spencer E, Hansen LD, Judd AM, Bell JD. Divalent cations increase lipid order in erythrocytes and susceptibility to secretory phospholipase A2. Biophys J 2004; 86:2251-60. [PMID: 15041664 PMCID: PMC1304075 DOI: 10.1016/s0006-3495(04)74283-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Elevated concentrations of intracellular calcium in erythrocytes increase membrane order and susceptibility to secretory phospholipase A2. We hypothesize that calcium aids the formation of domains of ordered lipids within erythrocyte membranes by interacting directly with the inner leaflet of the cell membrane. The interface of these domains with regions of more fluid lipids may create an environment with weakened neighbor-neighbor interactions that would facilitate phospholipid migration into the active site of bound secretory phospholipase A2. This hypothesis was investigated by determining the effects of seven other divalent ions on erythrocyte membrane properties. Changes in membrane order were assessed with steady-state fluorescence spectroscopy and two-photon microscopy with an environment-sensitive probe, laurdan. Each ion increased apparent membrane order in model membranes and in erythrocytes when introduced with an ionophore, suggesting that direct binding to the inner face of the membrane accounts for the effects of calcium on membrane fluidity. Furthermore, the degree to which ions affected membrane properties correlated with the ionic radius and electronegativity of the ions. Lastly, erythrocytes became more susceptible to enzyme hydrolysis in the presence of elevated intracellular levels of nickel and manganese, but not magnesium. These differences appeared related to the ability of the ions to induce a transition in erythrocyte shape.
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Affiliation(s)
- Rebekah S Vest
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, Utah 84620, USA
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Hamidinia SA, Shimelis OI, Tan B, Erdahl WL, Chapman CJ, Renkes GD, Taylor RW, Pfeiffer DR. Monensin mediates a rapid and selective transport of Pb(2+). Possible application of monensin for the treatment of Pb(2+) intoxication. J Biol Chem 2002; 277:38111-20. [PMID: 12080080 DOI: 10.1074/jbc.m205590200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The carboxylic acid ionophore monensin, known as an electroneutral Na(+) ionophore, an anticoccidial agent, and a growth-promoting feed additive in agriculture, is shown to be highly efficient as an ionophore for Pb(2+) and to be highly selective for Pb(2+) compared with other divalent cations. Monensin transports Pb(2+) by an electroneutral mechanism in which the complex PbMonOH is the transporting species. Electrogenic transport via the species PbMon(+) may also be possible. Monensin catalyzed Pb(2+) transport is little affected by Ca(2+), Mg(2+), or K(+) concentrations that are encountered in living systems. Na(+) is inhibitory, but its effectiveness at 100 mm does not exceed approximately 50%. The poor activity of monensin as an ionophore for divalent cations other than Pb(2+) is consistent with the pattern of complex formation constants observed in the mixed solvent 80% methanol/water. This pattern also explains why Ca(2+), Mg(2+), and K(+) are ineffective as inhibitors of Pb(2+) transport, but it does not fully explain the actions of Na(+), where kinetic features of the transport mechanism may also be important. When given to rats at 100 ppm in feed together with Pb(2+) at 100 ppm in drinking water, monensin reduces Pb accumulation in several organs and tissues. It also accelerates the excretion of Pb that was accumulated previously and produces this effect without depleting the organs of zinc or copper. Monensin, used alone or in combination with other agents, may be useful for the treatment of Pb intoxication.
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Affiliation(s)
- Shawn A Hamidinia
- Department of Molecular and Cellular Biochemistry, Ohio State University, Columbus, Ohio 43210, USA
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Abstract
The element compartmentation in cultured rat hepatocytes was studied by electron probe X-ray microanalysis of freeze-dried cryosections after exposure of the cells to the ionophores valinomycin, ionomycin or gramicidin A. The most striking effect of these ionophores is the decrease of the intracellular potassium/sodium ratio from values of approximately 10 under control conditions to values below 1 after application of the ionophores. Changes of sodium, potassium and chloride are similar in cytoplasm and nucleus. However, elemental changes are delayed or impeded in mitochondria with respect to the surrounding cytoplasm. The water portion of cytoplasm and mitochondria slightly increases. Besides that, each ionophore has specific effects on the intracellular ion distribution. As compared to gramicidin A and ionomycin, valinomycin does not change the intracellular chloride content. Ionomycin induces calcium accumulation in mitochondria. The cytotoxic effects of the studied ionophores on the intracellular element distribution are more complex than supposed from their ion selective properties in membranes.
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Affiliation(s)
- S Bolkent
- University of Istanbul, Department of Biology, Istanbul, Turkey
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Abstract
The transport mechanism and specificities of ionophore ETH-29 have been investigated in a highly defined phospholipid vesicle system, with the goal of facilitating the application of this compound to biological problems. ETH-129 transports Ca(2+) via an electrogenic mechanism, in contrast to A23187 and ionomycin, which function in a charge neutral manner. The rate of transport is a function of membrane potential, increasing by 3.9-fold per 59 mV over a broad range of that parameter. Rate is independent of the transmembrane pH gradient and strongly stimulated by the uncoupler carbonyl cyanide m-chlorophenylhydrazone when no external potential has been applied. The effect of uncoupler reflects the collapse of an opposing potential arising during Ca(2+) transport, but also reflects the formation of a mixed complex between the uncoupler, ETH-129, and Ca(2+) that readily permeates the vesicle membrane. Oleate does not substitute for the uncoupler in either regard. ETH-129 transports polyvalent cations according to the selectivity sequence La(3+) > Ca(2+) > Zn(2+) approximately equal to Sr(2+) > Co(2+) approximately equal to Ni(2+) approximately equal to Mn(2+), with the magnitude of the selectivity coefficients reflecting the cation concentration range considered. There is little or no activity for the transport of Na(+), K(+), and Mg(2+). These properties suggest that ETH-129 will be useful for investigating the consequences of a mitochondrial Ca(2+) overload in mammalian cells, which is difficult to pursue through the application of electroneutral ionophores.
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Affiliation(s)
- E Wang
- Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA
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Abstract
Recent biophysical studies on the interactions between lead and recombinant proteins and peptides that naturally bind zinc or calcium have provided unparalleled insights into the biological chemistry and molecular toxicology of lead. These studies lay the foundation for the rational design of improved methods for detecting and treating lead poisoning.
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Affiliation(s)
- H A Godwin
- Department of Chemistry, Northwestern University, Evanston, IL 60208-3113, USA.
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