101
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Manipulation of intracellular magnesium levels in Saccharomyces cerevisiae with deletion of magnesium transporters. Appl Microbiol Biotechnol 2007; 77:411-25. [DOI: 10.1007/s00253-007-1177-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2007] [Revised: 08/22/2007] [Accepted: 08/23/2007] [Indexed: 10/22/2022]
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102
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Ma JF. Syndrome of aluminum toxicity and diversity of aluminum resistance in higher plants. INTERNATIONAL REVIEW OF CYTOLOGY 2007; 264:225-52. [PMID: 17964924 DOI: 10.1016/s0074-7696(07)64005-4] [Citation(s) in RCA: 194] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
Aluminum (Al) is the most abundant metal in the earth's crust, while its soluble ionic form (Al(3+)) shows phytotoxicity, which is characterized by a rapid inhibition of root elongation. Aluminum targets multiple cellular sites by binding, resulting in disrupted structure and/or functions of the cell wall, plasma membrane, signal transduction pathway, and Ca homeostasis. On the other hand, some plant species have evolved mechanisms to cope with Al toxicity both externally and internally. The well-documented mechanisms for external detoxification of Al include the release of organic acid anions from roots and alkalination of the rhizosphere. Genes encoding transporters for Al-induced secretion of organic acid anions have been identified and characterized. Recent studies show that ABC transporters are involved in Al resistance. The internal detoxification of Al in Al-accumulating plants is achieved by the formation of nontoxic Al complexes with organic acids or other chelators and sequestration of these complexes in the vacuoles. In some plant species, Al shows beneficial effects on plant growth under particular conditions, although the exact mechanisms for these effects are unknown.
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Affiliation(s)
- Jian Feng Ma
- Research Institute for Bioresources, Okayama University, Kurashiki 710-0046, Japan
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103
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Payandeh J, Pai EF. A structural basis for Mg2+ homeostasis and the CorA translocation cycle. EMBO J 2006; 25:3762-73. [PMID: 16902408 PMCID: PMC1553185 DOI: 10.1038/sj.emboj.7601269] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2006] [Accepted: 07/13/2006] [Indexed: 01/07/2023] Open
Abstract
We describe the CorA Mg(2+) transporter homologue from Thermotoga maritima in complex with 12 divalent cations at 3.7 A resolution. One metal is found near the universally conserved GMN motif, apparently stabilized within the transmembrane region. This portion of the selectivity filter might discriminate between the size and preferred coordination geometry of hydrated substrates. CorA may further achieve specificity by requiring the sequential dehydration of substrates along the length of its approximately 55 A long pore. Ten metal sites identified within the cytoplasmic funnel domain are linked to long extensions of the pore helices and regulate the transport status of CorA. We have characterized this region as an intrinsic divalent cation sensor and provide evidence that it functions as a Mg(2+)-specific homeostatic molecular switch. A proteolytic protection assay, biophysical data, and comparison to a soluble domain structure from Archaeoglobus fulgidus have revealed the potential reaction coordinate for this diverse family of transport proteins.
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Affiliation(s)
- Jian Payandeh
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
- Division of Cancer Genomics & Proteomics, Ontario Cancer Institute, MaRS Centre, Toronto Medical Discovery Tower, Toronto, Ontario, Canada
- Division of Cancer Genomics & Proteomics, Ontario Cancer Institute, MaRS Centre, Toronto Medical Discovery Tower, 101 College Street, Toronto, Ontario, Canada M5G 1L7. Tel.: 416 581 7545; Fax: 416 581 7545; E-mail: or
| | - Emil F Pai
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
- Division of Cancer Genomics & Proteomics, Ontario Cancer Institute, MaRS Centre, Toronto Medical Discovery Tower, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Ontario, Canada
- Department of Molecular & Medical Genetics, University of Toronto, Toronto, Ontario, Canada
- Division of Cancer Genomics & Proteomics, Ontario Cancer Institute, MaRS Centre, Toronto Medical Discovery Tower, 101 College Street, Toronto, Ontario, Canada M5G 1L7. Tel.: 416 581 7545; Fax: 416 581 7545; E-mail: or
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104
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Zhong R, Burk DH, Nairn CJ, Wood-Jones A, Morrison WH, Ye ZH. Mutation of SAC1, an Arabidopsis SAC domain phosphoinositide phosphatase, causes alterations in cell morphogenesis, cell wall synthesis, and actin organization. THE PLANT CELL 2005; 17:1449-66. [PMID: 15805481 PMCID: PMC1091767 DOI: 10.1105/tpc.105.031377] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2005] [Accepted: 02/23/2005] [Indexed: 05/17/2023]
Abstract
SAC (for suppressor of actin) domain proteins in yeast and animals have been shown to modulate the levels of phosphoinositides, thereby regulating several cellular activities such as signal transduction, actin cytoskeleton organization, and vesicle trafficking. Nine genes encoding SAC domain-containing proteins are present in the Arabidopsis thaliana genome, but their roles in plant cellular functions and plant growth and development have not been characterized. In this report, we demonstrate the essential roles of one of the Arabidopsis SAC domain proteins, AtSAC1, in plant cellular functions. Mutation of the AtSAC1 gene in the fragile fiber7 (fra7) mutant caused a dramatic decrease in the wall thickness of fiber cells and vessel elements, thus resulting in a weak stem phenotype. The fra7 mutation also led to reduced length and aberrant shapes in fiber cells, pith cells, and trichomes and to an alteration in overall plant architecture. The AtSAC1 gene was found to be expressed in all tissues in elongating organs; however, it showed predominant expression in vascular tissues and fibers in nonelongating parts of stems. In vitro activity assay demonstrated that AtSAC1 exhibited phosphatase activity toward phosphatidylinositol 3,5-biphosphate. Subcellular localization studies showed that AtSAC1 was colocalized with a Golgi marker. Truncation of the C terminus by the fra7 mutation resulted in its localization in the cytoplasm but had no effect on phosphatase activity. Furthermore, examination of the cytoskeleton organization revealed that the fra7 mutation caused the formation of aberrant actin cables in elongating cells but had no effect on the organization of cortical microtubules. Together, these results provide genetic evidence that AtSAC1, a SAC domain phosphoinositide phosphatase, is required for normal cell morphogenesis, cell wall synthesis, and actin organization.
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Affiliation(s)
- Ruiqin Zhong
- Department of Plant Biology, University of Georgia, Athens, Georgia 30602
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105
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Shabala S, Hariadi Y. Effects of magnesium availability on the activity of plasma membrane ion transporters and light-induced responses from broad bean leaf mesophyll. PLANTA 2005; 221:56-65. [PMID: 15645306 DOI: 10.1007/s00425-004-1425-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2004] [Accepted: 10/14/2004] [Indexed: 05/20/2023]
Abstract
Considering the physiological significance of Mg homeostasis in plants, surprisingly little is known about the molecular and ionic mechanisms mediating Mg transport across the plasma membrane and the impact of Mg availability on transport processes at the plasmalemma. In this study, a non-invasive ion-selective microelectrode technique (MIFE) was used to characterize the effects of Mg availability on the activity of plasma membrane H+, K+, Ca2+, and Mg2+ transporters in the mesophyll cells of broad bean (Vicia faba L.) plants. Based on the stoichiometry of ion-flux changes and results of pharmacological experiments, we suggest that at least two mechanisms are involved in Mg2+ uptake across the plasma membrane of bean mesophyll cells. One of them is a non-selective cation channel, also permeable to K+ and Ca2+. The other mechanism, operating at concentrations below 30 microM, was speculated to be an H+/Mg+ exchanger. Experiments performed on leaves grown at different levels of Mg availability (from deficient to excessive) showed that Mg availability has a significant impact on the activity of plasma-membrane transporters for Ca2+, K+, and H+. We discuss the physiological significance of Mg-induced changes in leaf electrophysiological responses to light and the ionic mechanisms underlying this process.
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Affiliation(s)
- Sergey Shabala
- School of Agricultural Science, University of Tasmania, Private Bag 254, Hobart, TAS 7001, Australia.
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106
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Hermans C, Johnson GN, Strasser RJ, Verbruggen N. Physiological characterisation of magnesium deficiency in sugar beet: acclimation to low magnesium differentially affects photosystems I and II. PLANTA 2004; 220:344-55. [PMID: 15378366 DOI: 10.1007/s00425-004-1340-4] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2004] [Accepted: 06/17/2004] [Indexed: 05/03/2023]
Abstract
Magnesium deficiency in plants is a widespread problem, affecting productivity and quality in agriculture, yet at a physiological level it has been poorly studied in crop plants. Here, a physiological characterization of Mg deficiency in Beta vulgaris L., an important crop model, is presented. The impact of Mg deficiency on plant growth, mineral profile and photosynthetic activity was studied. The aerial biomass of plants decreased after 24 days of hydroponic culture in Mg-free nutrient solution, whereas the root biomass was unaffected. Analysis of mineral profiles revealed that Mg decreased more rapidly in roots than in shoots and that shoot Mg content could fall to 3 mg g(-1) DW without chlorosis development and with no effect on photosynthetic parameters. Sucrose accumulated in most recently expanded leaves before any loss in photosynthetic activity. During the development of Mg deficiency, the two photosystems showed sharply contrasting responses. Data were consistent with a down-regulation of PSII through a loss of antenna, and of PSI primarily through a loss of reaction centres. In each case, the net result was a decrease in the overall rate of linear electron transport, preventing an excess of reductant being produced during conditions under which sucrose export away from mature leaf was restricted.
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Affiliation(s)
- Christian Hermans
- Laboratoire de Physiologie et de Génétique Moléculaire des Plantes, Université Libre de Bruxelles, 1050 Brussels, Belgium
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107
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Abstract
Classification of proteins into families is one of the main goals of functional analysis. Proteins are usually assigned to a family on the basis of the presence of family-specific patterns, domains, or structural elements. Whereas proteins belonging to the same family are generally similar to each other, the extent of similarity varies widely across families. Some families are characterized by short, well-defined motifs, whereas others contain longer, less-specific motifs. We present a simple method for visualizing such differences. We applied our method to the Arabidopsis thaliana families listed at The Arabidopsis Information Resource (TAIR) Web site and for 76% of the nontrivial families (families with more than one member), our method identifies simple similarity measures that are necessary and sufficient to cluster members of the family together. Our visualization method can be used as part of an annotation pipeline to identify potentially incorrectly defined families. We also describe how our method can be extended to identify novel families and to assign unclassified proteins into known families.
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Affiliation(s)
- Vamsi Veeramachaneni
- Department of Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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108
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Blaudez D, Kohler A, Martin F, Sanders D, Chalot M. Poplar metal tolerance protein 1 confers zinc tolerance and is an oligomeric vacuolar zinc transporter with an essential leucine zipper motif. THE PLANT CELL 2003; 15:2911-28. [PMID: 14630973 PMCID: PMC282827 DOI: 10.1105/tpc.017541] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2003] [Accepted: 09/18/2003] [Indexed: 05/18/2023]
Abstract
Cation diffusion facilitator (CDF) proteins are a recently discovered family of cation efflux transporters that might play an essential role in metal homeostasis and tolerance. Here, we describe the identification, characterization, and localization of PtdMTP1, a member of the CDF family from the hybrid poplar Populus trichocarpa x Populus deltoides. PtdMTP1 is expressed constitutively and ubiquitously, although at low levels. Heterologous expression in yeast showed that PtdMTP1 was able to complement the hypersensitivity of mutant strains to Zn but not to other metals, including Cd, Co, Mn, and Ni. PtdMTP1 fused to green fluorescent protein localized to the vacuolar membrane both in yeast and in plant cells, consistent with a function of PtdMTP1 in zinc sequestration. Overexpression of PtdMTP1 in Arabidopsis confers Zn tolerance. We show that PtdMTP1, when expressed in yeast and Arabidopsis, forms homooligomers, a novel feature of CDF members. Oligomer formation is disrupted by reducing agents, indicating possible disulfide bridge formation. PtdMTP1 also contains a conserved Leu zipper motif. Although not necessary for oligomer formation, Leu residues within this motif are required for PtdMTP1 functional activity.
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Affiliation(s)
- Damien Blaudez
- Biology Department, University of York, York YO10 5YW, United Kingdom
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109
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Kerkeb L, Krämer U. The role of free histidine in xylem loading of nickel in Alyssum lesbiacum and Brassica juncea. PLANT PHYSIOLOGY 2003; 131:716-24. [PMID: 12586895 PMCID: PMC166847 DOI: 10.1104/pp102.010686] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2002] [Revised: 08/04/2002] [Accepted: 10/27/2002] [Indexed: 05/18/2023]
Abstract
Exposure of the hyperaccumulator Alyssum lesbiacum to nickel (Ni) is known to result in a dose-dependent increase in xylem sap concentrations of Ni and the chelator free histidine (His). Addition of equimolar concentrations of exogenous L-His to an Ni-amended hydroponic rooting medium enhances Ni flux into the xylem in the nonaccumulator Alyssum montanum, and, as reported here, in Brassica juncea L. cv Vitasso. In B. juncea, reducing the entry of L-His into the root by supplying D-His instead of L-His, or L-His in the presence of a 10-fold excess of L-alanine, did not affect root Ni uptake, but reduced Ni release into the xylem. Compared with B. juncea, root His concentrations were constitutively about 4.4-fold higher in A. lesbiacum, and did not increase within 9 h of exposure to Ni. Cycloheximide did not affect root His or Ni concentrations, but strongly decreased the release of His and Ni from the root into the xylem of A. lesbiacum, whereas xylem sap concentrations of Ca and Mg remained unaffected. Near-quantitative chelation of Ni with nitrilotriacetate in the rooting medium did not enhance Ni flux into the xylem of A. lesbiacum and B. juncea, suggesting the absence of a significant apoplastic pathway for Ni entry into the xylem. The data suggest that in B. juncea roots, Ni(2+) uptake is independent of simultaneous uptake of His. In both species, enhanced release of Ni into the xylem is associated with concurrent release of His from an increased root free His pool.
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Affiliation(s)
- Loubna Kerkeb
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, D-14476 Golm, Germany
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110
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Hawkesford MJ. Transporter gene families in plants: the sulphate transporter gene family - redundancy or specialization? PHYSIOLOGIA PLANTARUM 2003; 117:155-163. [PMID: 0 DOI: 10.1034/j.1399-3054.2003.00034.x] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
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111
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Schwacke R, Schneider A, van der Graaff E, Fischer K, Catoni E, Desimone M, Frommer WB, Flügge UI, Kunze R. ARAMEMNON, a novel database for Arabidopsis integral membrane proteins. PLANT PHYSIOLOGY 2003; 131:16-26. [PMID: 12529511 PMCID: PMC166783 DOI: 10.1104/pp.011577] [Citation(s) in RCA: 525] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2002] [Revised: 08/28/2002] [Accepted: 10/14/2002] [Indexed: 05/17/2023]
Abstract
A specialized database (DB) for Arabidopsis membrane proteins, ARAMEMNON, was designed that facilitates the interpretation of gene and protein sequence data by integrating features that are presently only available from individual sources. Using several publicly available prediction programs, putative integral membrane proteins were identified among the approximately 25,500 proteins in the Arabidopsis genome DBs. By averaging the predictions from seven programs, approximately 6,500 proteins were classified as transmembrane (TM) candidate proteins. Some 1,800 of these contain at least four TM spans and are possibly linked to transport functions. The ARAMEMNON DB enables direct comparison of the predictions of seven different TM span computation programs and the predictions of subcellular localization by eight signal peptide recognition programs. A special function displays the proteins related to the query and dynamically generates a protein family structure. As a first set of proteins from other organisms, all of the approximately 700 putative membrane proteins were extracted from the genome of the cyanobacterium Synechocystis sp. and incorporated in the ARAMEMNON DB. The ARAMEMNON DB is accessible at the URL http://aramemnon.botanik.uni-koeln.de.
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Affiliation(s)
- Rainer Schwacke
- Universität zu Köln, Botanisches Institut, Gyrhofstrasse 15, 50931 Köln, Germany.
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112
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Schwacke R, Schneider A, van der Graaff E, Fischer K, Catoni E, Desimone M, Frommer WB, Flügge UI, Kunze R. ARAMEMNON, a novel database for Arabidopsis integral membrane proteins. PLANT PHYSIOLOGY 2003; 131:16-26. [PMID: 12529511 DOI: 10.1104/pp011577] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
A specialized database (DB) for Arabidopsis membrane proteins, ARAMEMNON, was designed that facilitates the interpretation of gene and protein sequence data by integrating features that are presently only available from individual sources. Using several publicly available prediction programs, putative integral membrane proteins were identified among the approximately 25,500 proteins in the Arabidopsis genome DBs. By averaging the predictions from seven programs, approximately 6,500 proteins were classified as transmembrane (TM) candidate proteins. Some 1,800 of these contain at least four TM spans and are possibly linked to transport functions. The ARAMEMNON DB enables direct comparison of the predictions of seven different TM span computation programs and the predictions of subcellular localization by eight signal peptide recognition programs. A special function displays the proteins related to the query and dynamically generates a protein family structure. As a first set of proteins from other organisms, all of the approximately 700 putative membrane proteins were extracted from the genome of the cyanobacterium Synechocystis sp. and incorporated in the ARAMEMNON DB. The ARAMEMNON DB is accessible at the URL http://aramemnon.botanik.uni-koeln.de.
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Affiliation(s)
- Rainer Schwacke
- Universität zu Köln, Botanisches Institut, Gyrhofstrasse 15, 50931 Köln, Germany.
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113
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Konrad M, Weber S. Recent advances in molecular genetics of hereditary magnesium-losing disorders. J Am Soc Nephrol 2003; 14:249-60. [PMID: 12506158 DOI: 10.1097/01.asn.0000049161.60740.ce] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Recent advances in molecular genetics in hereditary hypomagnesemia substantiated the role of a variety of genes and their encoded proteins in human magnesium transport mechanisms. This knowledge on underlying genetic defects helps to distinguish different clinical subtypes and gives first insight into molecular components involved in magnesium transport. By mutation analysis and functional protein studies, novel pathophysiologic aspects were elucidated. For some of these disorders, transgenic animal models were generated to study genotype-phenotype relations and disease pathology. This review will discuss genetic and clinical aspects of familial disorders associated with magnesium wasting and focuses on the recent progress that has been made in molecular genetics. Besides isolated renal forms of hereditary hypomagnesemia, the following disorders will also be presented: familial hypomagnesemia with hypercalciuria and nephrocalcinosis, hypomagnesemia with secondary hypocalcemia, Ca2+/Mg2+-sensing receptor-associated disorders, and disorders associated with renal salt-wasting and hypokalemic metabolic alkalosis, comprising the Gitelman syndrome and the Bartter-like syndromes.
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