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Dabravolski SA, Isayenkov SV. Recent updates on the physiology and evolution of plant TPK/KCO channels. FUNCTIONAL PLANT BIOLOGY : FPB 2023; 50:17-28. [PMID: 36220140 DOI: 10.1071/fp22117] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 09/21/2022] [Indexed: 06/16/2023]
Abstract
Plant vacuoles are the main cellular reservoirs to store K+ . The vacuolar K+ channels play a pivotal role in K+ exchange between cytosol and vacuolar sap. Among vacuolar K+ transporters, the Two Pore Potassium Channels (TPKs) are highly selective K+ channels present in most or all plant vacuoles and could be involved in various plant stress responses and developmental processes. Although the majority of TPK members have a vacuolar specialisation, some TPKs display different membrane localisation including the plasma membrane, tonoplast of protein storage vacuoles and probably chloroplast membranes. The functional properties as well as physiological roles of TPKs remains largely unexplored. In this review, we have collected recent data about the physiology, structure, functionality and evolution of TPK/KCO3 channels. We also critically evaluate the latest findings on the biological role, physiological functions, and regulation of TPK/KCO3 channels in relation to their structure and phylogenetic position. The possible role of TPK/KCO3 channels in plant tolerance to various abiotic stresses is summarised, and the future priority directions for TPK/KCO3 studies are addressed.
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Affiliation(s)
- Siarhei A Dabravolski
- Department of Biotechnology Engineering, ORT Braude College, Snunit 51, P.O. Box 78, Karmiel 2161002, Israel
| | - Stanislav V Isayenkov
- International Research Centre for Environmental Membrane Biology, Foshan University, Foshan, China; and Department of Plant Food Products and Biofortification, Institute of Food Biotechnology and Genomics NAS of Ukraine, Kyiv, Ukraine
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2
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Tanudjaja E, Hoshi N, Yamamoto K, Ihara K, Furuta T, Tsujii M, Ishimaru Y, Uozumi N. Two Trk/Ktr/HKT-type potassium transporters, TrkG and TrkH, perform distinct functions in Escherichia coli K-12. J Biol Chem 2022; 299:102846. [PMID: 36586436 PMCID: PMC9898762 DOI: 10.1016/j.jbc.2022.102846] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 12/19/2022] [Accepted: 12/23/2022] [Indexed: 12/29/2022] Open
Abstract
Escherichia coli K-12 possesses two versions of Trk/Ktr/HKT-type potassium ion (K+) transporters, TrkG and TrkH. The current paradigm is that TrkG and TrkH have largely identical characteristics, and little information is available regarding their functional differences. Here, we show using cation uptake experiments with K+ transporter knockout mutants that TrkG and TrkH have distinct ion transport activities and physiological roles. K+-transport by TrkG required Na+, whereas TrkH-mediated K+ uptake was not affected by Na+. An aspartic acid located five residues away from a critical glycine in the third pore-forming region might be involved in regulation of Na+-dependent activation of TrkG. In addition, we found that TrkG but not TrkH had Na+ uptake activity. Our analysis of K+ transport mutants revealed that TrkH supported cell growth more than TrkG; however, TrkG was able to complement loss of TrkH-mediated K+ uptake in E. coli. Furthermore, we determined that transcription of trkG in E. coli was downregulated but not completely silenced by the xenogeneic silencing factor H-NS (histone-like nucleoid structuring protein or heat-stable nucleoid-structuring protein). Taken together, the transport function of TrkG is clearly distinct from that of TrkH, and TrkG seems to have been accepted by E. coli during evolution as a K+ uptake system that coexists with TrkH.
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Affiliation(s)
- Ellen Tanudjaja
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, Japan
| | - Naomi Hoshi
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, Japan
| | | | - Kunio Ihara
- Center for Gene Research, Nagoya University, Nagoya, Japan
| | - Tadaomi Furuta
- School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
| | - Masaru Tsujii
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, Japan
| | - Yasuhiro Ishimaru
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, Japan
| | - Nobuyuki Uozumi
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, Japan.
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3
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Yamanashi T, Uchiyama T, Saito S, Higashi T, Ikeda H, Kikunaga H, Yamagami M, Ishimaru Y, Uozumi N. Potassium transporter KUP9 participates in K + distribution in roots and leaves under low K + stress. STRESS BIOLOGY 2022; 2:52. [PMID: 37676337 PMCID: PMC10441886 DOI: 10.1007/s44154-022-00074-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Accepted: 11/09/2022] [Indexed: 09/08/2023]
Abstract
Potassium (K) is a major essential element in plant cells, and KUP/HAK/KT-type K+ transporters participate in the absorption of K+ into roots and in the long-distance transport to above-ground parts. In Arabidopsis thaliana, KUP9 is involved in the transport of K+ and Cs+ in roots. In this study, we investigated KUP9 function in relation to the K+ status of the plant. The expression of KUP9 was upregulated in older leaves on K+-depleted medium, compared to the expression of the other 12 KUP genes in the KUP/HAK/KT family in Arabidopsis. When grown on low K+ medium, the kup9 mutant had reduced chlorophyll content in seedlings and chlorosis in older rosette leaves. Tissue-specific expression of KUP9 determined by KUP9 promoter:GUS assay depended on the K+ status of the plants: In K+ sufficient medium, KUP9 was expressed in the leaf blade towards the leaf tip, whereas in K+ depleted medium expression was mainly found in the petioles. In accordance with this, K+ accumulated in the roots of kup9 plants. The short-term 43K+ tracer measurement showed that 43K was transferred at a lower rate in roots and shoots of kup9, compared to the wild type. These data show that KUP9 participates in the distribution of K+ in leaves and K+ absorption in roots under low K+ conditions.
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Affiliation(s)
- Taro Yamanashi
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, 980-8579, Japan
| | - Takeshi Uchiyama
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, 980-8579, Japan
| | - Shunya Saito
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, 980-8579, Japan
| | - Taiki Higashi
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, 980-8579, Japan
| | - Hayato Ikeda
- Research Center for Electron Photon Science, Tohoku University, Sendai, 980-0826, Japan
- Cyclotron and Radioisotope Center, Tohoku University, Sendai, 980-8578, Japan
| | - Hidetoshi Kikunaga
- Research Center for Electron Photon Science, Tohoku University, Sendai, 980-0826, Japan
| | - Mutsumi Yamagami
- Institute for Environmental Sciences, Rokkasho, Kamikita, Aomori, 039-3212, Japan
| | - Yasuhiro Ishimaru
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, 980-8579, Japan
| | - Nobuyuki Uozumi
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, 980-8579, Japan.
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4
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Ankit A, Kamali S, Singh A. Genomic & structural diversity and functional role of potassium (K +) transport proteins in plants. Int J Biol Macromol 2022; 208:844-857. [PMID: 35367275 DOI: 10.1016/j.ijbiomac.2022.03.179] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Revised: 03/11/2022] [Accepted: 03/25/2022] [Indexed: 01/03/2023]
Abstract
Potassium (K+) is an essential macronutrient for plant growth and productivity. It is the most abundant cation in plants and is involved in various cellular processes. Variable K+ availability is sensed by plant roots, consequently K+ transport proteins are activated to optimize K+ uptake. In addition to K+ uptake and translocation these proteins are involved in other important physiological processes like transmembrane voltage regulation, polar auxin transport, maintenance of Na+/K+ ratio and stomata movement during abiotic stress responses. K+ transport proteins display tremendous genomic and structural diversity in plants. Their key structural features, such as transmembrane domains, N-terminal domains, C-terminal domains and loops determine their ability of K+ uptake and transport and thus, provide functional diversity. Most K+ transporters are regulated at transcriptional and post-translational levels. Genetic manipulation of key K+ transporters/channels could be a prominent strategy for improving K+ utilization efficiency (KUE) in plants. This review discusses the genomic and structural diversity of various K+ transport proteins in plants. Also, an update on the function of K+ transport proteins and their regulatory mechanism in response to variable K+ availability, in improving KUE, biotic and abiotic stresses is provided.
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Affiliation(s)
- Ankit Ankit
- National Institute of Plant Genome Research, New Delhi 110067, India
| | | | - Amarjeet Singh
- National Institute of Plant Genome Research, New Delhi 110067, India.
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5
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Dabravolski SA, Isayenkov SV. New Insights into Plant TPK Ion Channel Evolution. PLANTS (BASEL, SWITZERLAND) 2021; 10:plants10112328. [PMID: 34834689 PMCID: PMC8619664 DOI: 10.3390/plants10112328] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 10/27/2021] [Accepted: 10/27/2021] [Indexed: 05/14/2023]
Abstract
Potassium (K) is a crucial element of plant nutrition, involved in many physiological and molecular processes. K+ membrane transporters are playing a pivotal role in K+ transport and tissue distribution as well as in various plant stress responses and developmental processes. Two-pore K+-channels (TPKs) are essential to maintain plant K+ homeostasis and are mainly involved in potassium transport from the vacuoles to the cytosol. Besides vacuolar specialization, some TPK members display different membrane localization including plasma membrane, protein storage vacuole membrane, and probably the organelles. In this manuscript, we elucidate the evolution of the voltage-independent TPK (two-pore K+-channels) family, which could be represented in some species by one pore, K+-inward rectifier (Kir)-like channels. A comprehensive investigation of existing databases and application of modern bioinformatic tools allowed us to make a detailed phylogenetic inventory of TPK/KCO3 (KCO: potassium channel, outward rectifying) channels through many taxa and gain insight into the evolutionary origin of TPK family proteins. Our results reveal the fundamental evolutional difference between the first and second pores, traced throughout multiple taxa variations in the ion selection filter motif, presence of thansposon, and methylation site in the proximity of some KCO members and suggest virus-mediated horizontal transfer of a KCO3-like ancestor by viruses. Additionally, we suggest several interconnected hypotheses to explain the obtained results and provide a theoretical background for future experimental validation.
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Affiliation(s)
- Siarhei A. Dabravolski
- Department of Clinical Diagnostics, Vitebsk State Academy of Veterinary Medicine [UO VGAVM], 21002 Vitebsk, Belarus;
| | - Stanislav V. Isayenkov
- International Research Center for Environmental Membrane Biology, Foshan University, Foshan 528000, China
- Department of Plant Food Products and Biofortification, Institute of Food Biotechnology and Genomics NAS of Ukraine, 04123 Kyiv, Ukraine
- Correspondence:
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6
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Ródenas R, Ragel P, Nieves-Cordones M, Martínez-Martínez A, Amo J, Lara A, Martínez V, Quintero FJ, Pardo JM, Rubio F. Insights into the mechanisms of transport and regulation of the arabidopsis high-affinity K+ transporter HAK51. PLANT PHYSIOLOGY 2021; 185:1860-1874. [PMID: 33595056 PMCID: PMC8133630 DOI: 10.1093/plphys/kiab028] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 01/11/2021] [Indexed: 05/02/2023]
Abstract
The high-affinity K+ transporter HAK5 from Arabidopsis (Arabidopsis thaliana) is essential for K+ acquisition and plant growth at low micromolar K+ concentrations. Despite its functional relevance in plant nutrition, information about functional domains of HAK5 is scarce. Its activity is enhanced by phosphorylation via the AtCIPK23/AtCBL1-9 complex. Based on the recently published three-dimensionalstructure of the bacterial ortholog KimA from Bacillus subtilis, we have modeled AtHAK5 and, by a mutational approach, identified residues G67, Y70, G71, D72, D201, and E312 as essential for transporter function. According to the structural model, residues D72, D201, and E312 may bind K+, whereas residues G67, Y70, and G71 may shape the selective filter for K+, which resembles that of K+shaker-like channels. In addition, we show that phosphorylation of residue S35 by AtCIPK23 is required for reaching maximal transport activity. Serial deletions of the AtHAK5 C-terminus disclosed the presence of an autoinhibitory domain located between residues 571 and 633 together with an AtCIPK23-dependent activation domain downstream of position 633. Presumably, autoinhibition of AtHAK5 is counteracted by phosphorylation of S35 by AtCIPK23. Our results provide a molecular model for K+ transport and describe CIPK-CBL-mediated regulation of plant HAK transporters.
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Affiliation(s)
- Reyes Ródenas
- Departamento de Nutrición Vegetal, Centro de Edafología y Biología Aplicada del Segura, Consejo Superior de Investigaciones Científicas, Campus de Espinardo, 30100 Murcia, Spain
- Present address: Plant Science Research Laboratory (LRSV), UMR5546 CNRS/Université Toulouse 3, 24 chemin de Borde Rouge, 31320 Auzeville-Tolosane, France
| | - Paula Ragel
- Instituto de Bioquímica Vegetal y Fotosíntesis, cic-Cartuja, Consejo Superior de Investigaciones Científicas-Universidad de Sevilla, 41092 Sevilla, Spain
- Present address: Centre for Organismal Studies (COS), Department of Cell Biology, Heidelberg University, Heidelberg, Germany
| | - Manuel Nieves-Cordones
- Departamento de Nutrición Vegetal, Centro de Edafología y Biología Aplicada del Segura, Consejo Superior de Investigaciones Científicas, Campus de Espinardo, 30100 Murcia, Spain
| | - Almudena Martínez-Martínez
- Departamento de Nutrición Vegetal, Centro de Edafología y Biología Aplicada del Segura, Consejo Superior de Investigaciones Científicas, Campus de Espinardo, 30100 Murcia, Spain
| | - Jesús Amo
- Departamento de Nutrición Vegetal, Centro de Edafología y Biología Aplicada del Segura, Consejo Superior de Investigaciones Científicas, Campus de Espinardo, 30100 Murcia, Spain
| | - Alberto Lara
- Departamento de Nutrición Vegetal, Centro de Edafología y Biología Aplicada del Segura, Consejo Superior de Investigaciones Científicas, Campus de Espinardo, 30100 Murcia, Spain
| | - Vicente Martínez
- Departamento de Nutrición Vegetal, Centro de Edafología y Biología Aplicada del Segura, Consejo Superior de Investigaciones Científicas, Campus de Espinardo, 30100 Murcia, Spain
| | - Francisco J Quintero
- Instituto de Bioquímica Vegetal y Fotosíntesis, cic-Cartuja, Consejo Superior de Investigaciones Científicas-Universidad de Sevilla, 41092 Sevilla, Spain
| | - Jose M Pardo
- Instituto de Bioquímica Vegetal y Fotosíntesis, cic-Cartuja, Consejo Superior de Investigaciones Científicas-Universidad de Sevilla, 41092 Sevilla, Spain
| | - Francisco Rubio
- Departamento de Nutrición Vegetal, Centro de Edafología y Biología Aplicada del Segura, Consejo Superior de Investigaciones Científicas, Campus de Espinardo, 30100 Murcia, Spain
- Author for communication:
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7
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Cation Transporters of Candida albicans-New Targets to Fight Candidiasis? Biomolecules 2021; 11:biom11040584. [PMID: 33923411 PMCID: PMC8073359 DOI: 10.3390/biom11040584] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Accepted: 04/14/2021] [Indexed: 02/07/2023] Open
Abstract
Candidiasis is the wide-spread fungal infection caused by numerous strains of yeast, with the prevalence of Candida albicans. The current treatment of candidiasis is becoming rather ineffective and costly owing to the emergence of resistant strains; hence, the exploration of new possible drug targets is necessary. The most promising route is the development of novel antibiotics targeting this pathogen. In this review, we summarize such candidates found in C. albicans and those involved in the transport of (metal) cations, as the latter are essential for numerous processes within the cell; hence, disruption of their fluxes can be fatal for C. albicans.
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8
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Stautz J, Hellmich Y, Fuss MF, Silberberg JM, Devlin JR, Stockbridge RB, Hänelt I. Molecular Mechanisms for Bacterial Potassium Homeostasis. J Mol Biol 2021; 433:166968. [PMID: 33798529 DOI: 10.1016/j.jmb.2021.166968] [Citation(s) in RCA: 51] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 03/11/2021] [Accepted: 03/22/2021] [Indexed: 10/21/2022]
Abstract
Potassium ion homeostasis is essential for bacterial survival, playing roles in osmoregulation, pH homeostasis, regulation of protein synthesis, enzyme activation, membrane potential adjustment and electrical signaling. To accomplish such diverse physiological tasks, it is not surprising that a single bacterium typically encodes several potassium uptake and release systems. To understand the role each individual protein fulfills and how these proteins work in concert, it is important to identify the molecular details of their function. One needs to understand whether the systems transport ions actively or passively, and what mechanisms or ligands lead to the activation or inactivation of individual systems. Combining mechanistic information with knowledge about the physiology under different stress situations, such as osmostress, pH stress or nutrient limitation, one can identify the task of each system and deduce how they are coordinated with each other. By reviewing the general principles of bacterial membrane physiology and describing the molecular architecture and function of several bacterial K+-transporting systems, we aim to provide a framework for microbiologists studying bacterial potassium homeostasis and the many K+-translocating systems that are still poorly understood.
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Affiliation(s)
- Janina Stautz
- Institute of Biochemistry, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Yvonne Hellmich
- Institute of Biochemistry, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Michael F Fuss
- Institute of Biochemistry, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Jakob M Silberberg
- Institute of Biochemistry, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Jason R Devlin
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, United States
| | - Randy B Stockbridge
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, United States.
| | - Inga Hänelt
- Institute of Biochemistry, Goethe University Frankfurt, Frankfurt am Main, Germany.
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9
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Uehara C, Takeda K, Ibuki T, Furuta T, Hoshi N, Tanudjaja E, Uozumi N. Analysis of Arabidopsis TPK2 and KCO3 reveals structural properties required for K + channel function. Channels (Austin) 2020; 14:336-346. [PMID: 33016199 PMCID: PMC7757853 DOI: 10.1080/19336950.2020.1825894] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Arabidopsis thaliana contains five tandem-pore domain potassium channels, TPK1-TPK5 and the related one-pore domain potassium channel, KCO3. Although KCO3 is unlikely to be an active channel, it still has a physiological role in plant cells. TPK2 is most similar to KCO3 and both are localized to the tonoplast. However, their function remains poorly understood. Here, taking advantage of the similarities between TPK2 and KCO3, we evaluated Ca2+ binding to the EF hands in TPK2, and the elements of KCO3 required for K+ channel activity. Presence of both EF-hand motifs in TPK2 resulted in Ca2+ binding, but EF1 or EF2 alone failed to interact with Ca2+. The EF hands were not required for K+ transport activity. EF1 contains two cysteines separated by two amino acids. Replacement of both cysteines with serines in TPK2 increased Ca2+ binding. We generated a two-pore domain chimeric K+ channel by replacing the missing pore region in KCO3 with a pore domain of TPK2. Alternatively, we generated two versions of simple one-pore domain K+ channels by removal of an extra region from KCO3. The chimera and one of the simple one-pore variants were functional channels. This strongly suggests that KCO3 is not a pseudogene and KCO3 retains components required for the formation of a functional K+ channel and oligomerization. Our results contribute to our understanding of the structural properties required for K+ channel activity.
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Affiliation(s)
- Chihiro Uehara
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University , Sendai, Japan
| | - Kota Takeda
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University , Sendai, Japan.,Bioscience and Biotechnology Center, Nagoya University , Nagoya, Japan
| | - Tatsuki Ibuki
- Bioscience and Biotechnology Center, Nagoya University , Nagoya, Japan
| | - Tadaomi Furuta
- School of Life Science and Technology, Tokyo Institute of Technology , Yokohama, Japan
| | - Naomi Hoshi
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University , Sendai, Japan
| | - Ellen Tanudjaja
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University , Sendai, Japan
| | - Nobuyuki Uozumi
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University , Sendai, Japan
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10
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Ding B, Zhang X, Xu Y, An L, Liu X, Su Q. The bacterial potassium transporter gene MbtrkH improves K+ uptake in yeast and tobacco. PLoS One 2020; 15:e0236246. [PMID: 32804956 PMCID: PMC7430745 DOI: 10.1371/journal.pone.0236246] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2019] [Accepted: 07/01/2020] [Indexed: 11/19/2022] Open
Abstract
K+ is an essential nutrient for plant growth and is responsible for many important physiological processes. K+ deficiency leads to crop yield losses, and overexpression of K+ transporter genes has been proven to be an effective way to resolve this problem. However, current research on the overexpression of K+ transporter genes is limited to plant sources. TrkH is a bacterial K+ transporter whose function generally depends on the regulation of TrkA. To date, whether TrkH can improve K+ uptake in eukaryotic organisms is still unknown. In this study, a novel MbtrkH gene was cloned from marine microbial metagenomic DNA. Functional complementation and K+-depletion analyses revealed that MbTrkH functions in K+ uptake in the K+-deficient yeast strain CY162. Moreover, K+-depletion assays revealed that MbtrkH overexpression improves plant K+ uptake. K+ hydroponic culture experiments showed that, compared with WT tobacco lines, MbtrkH transgenic tobacco lines had significantly greater fresh weights, dry weights and K+ contents. These results indicate that MbTrkH promotes K+ uptake independently of TrkA in eukaryotes and provide a new strategy for improving K+-use efficiency in plants.
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Affiliation(s)
- Baojuan Ding
- School of Bioengineering, Dalian University of Technology, Dalian, P. R. China
| | - Xiaoyan Zhang
- School of Bioengineering, Dalian University of Technology, Dalian, P. R. China
| | - Yongsheng Xu
- School of Bioengineering, Dalian University of Technology, Dalian, P. R. China
| | - Lijia An
- School of Bioengineering, Dalian University of Technology, Dalian, P. R. China
| | - Xiangguo Liu
- Institute of Agricultural Biotechnology, Jilin Academy of Agricultural Sciences, Changchun, P. R. China
| | - Qiao Su
- School of Bioengineering, Dalian University of Technology, Dalian, P. R. China
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11
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Tascón I, Sousa JS, Corey RA, Mills DJ, Griwatz D, Aumüller N, Mikusevic V, Stansfeld PJ, Vonck J, Hänelt I. Structural basis of proton-coupled potassium transport in the KUP family. Nat Commun 2020; 11:626. [PMID: 32005818 PMCID: PMC6994465 DOI: 10.1038/s41467-020-14441-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Accepted: 01/10/2020] [Indexed: 12/05/2022] Open
Abstract
Potassium homeostasis is vital for all organisms, but is challenging in single-celled organisms like bacteria and yeast and immobile organisms like plants that constantly need to adapt to changing external conditions. KUP transporters facilitate potassium uptake by the co-transport of protons. Here, we uncover the molecular basis for transport in this widely distributed family. We identify the potassium importer KimA from Bacillus subtilis as a member of the KUP family, demonstrate that it functions as a K+/H+ symporter and report a 3.7 Å cryo-EM structure of the KimA homodimer in an inward-occluded, trans-inhibited conformation. By introducing point mutations, we identify key residues for potassium and proton binding, which are conserved among other KUP proteins. KUP transporters facilitate potassium uptake by the co-transport of protons and are key players in potassium homeostasis. Here authors identify the potassium importer KimA from Bacillus subtilis as a new member of the KUP transporter family and show the cryo-EM structure of KimA in an inward-occluded, trans-inhibited conformation.
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Affiliation(s)
- Igor Tascón
- Institute of Biochemistry, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Joana S Sousa
- Department of Structural Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Robin A Corey
- Department of Biochemistry, University of Oxford, Oxford, UK
| | - Deryck J Mills
- Department of Structural Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - David Griwatz
- Institute of Biochemistry, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Nadine Aumüller
- Institute of Biochemistry, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Vedrana Mikusevic
- Institute of Biochemistry, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Phillip J Stansfeld
- Department of Biochemistry, University of Oxford, Oxford, UK.,School of Life Sciences & Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK
| | - Janet Vonck
- Department of Structural Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany.
| | - Inga Hänelt
- Institute of Biochemistry, Goethe University Frankfurt, Frankfurt am Main, Germany.
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12
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13
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Tsujii M, Kera K, Hamamoto S, Kuromori T, Shikanai T, Uozumi N. Evidence for potassium transport activity of Arabidopsis KEA1-KEA6. Sci Rep 2019; 9:10040. [PMID: 31296940 PMCID: PMC6624313 DOI: 10.1038/s41598-019-46463-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 06/24/2019] [Indexed: 12/12/2022] Open
Abstract
Arabidopsis thaliana contains the putative K+ efflux transporters KEA1-KEA6, similar to KefB and KefC of Escherichia coli. KEA1-KEA3 are involved in the regulation of photosynthetic electron transport and chloroplast development. KEA4-KEA6 mediate pH regulation of the endomembrane network during salinity stress. However, the ion transport activities of KEA1-KEA6 have not been directly characterized. In this study, we used an E. coli expression system to examine KEA activity. KEA1-KEA3 and KEA5 showed bi-directional K+ transport activity, whereas KEA4 and KEA6 functioned as a K+ uptake system. The thylakoid membrane-localized Na+/H+ antiporter NhaS3 from the model cyanobacterium Synechocystis is the closest homolog of KEA3. Changing the putative Na+/H+ selective site of KEA3 (Gln-Asp) to that of NhaS3 (Asp-Asp) did not alter the ion selectivity without loss of K+ transport activity. The first residue in the conserved motif was not a determinant for K+ or Na+ selectivity. Deletion of the possible nucleotide-binding KTN domain from KEA3 lowered K+ transport activity, indicating that the KTN domain was important for this function. The KEA3-G422R mutation discovered in the Arabidopsis dpgr mutant increased K+ transport activity, consistent with the mutant phenotype. These results indicate that Arabidopsis KEA1-KEA6 act as K+ transport systems, and support the interpretation that KEA3 promotes dissipation of ΔpH in the thylakoid membrane.
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Affiliation(s)
- Masaru Tsujii
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aobayama 6-6-07, Sendai, 980-8579, Japan
| | - Kota Kera
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aobayama 6-6-07, Sendai, 980-8579, Japan
| | - Shin Hamamoto
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aobayama 6-6-07, Sendai, 980-8579, Japan
| | - Takashi Kuromori
- RIKEN Center for Sustainable Resource Science, Wako, Saitama, 351-0198, Japan
| | - Toshiharu Shikanai
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan
| | - Nobuyuki Uozumi
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aobayama 6-6-07, Sendai, 980-8579, Japan.
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The KupA and KupB Proteins of Lactococcus lactis IL1403 Are Novel c-di-AMP Receptor Proteins Responsible for Potassium Uptake. J Bacteriol 2019; 201:JB.00028-19. [PMID: 30745376 DOI: 10.1128/jb.00028-19] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 02/04/2019] [Indexed: 12/13/2022] Open
Abstract
Cyclic di-AMP (c-di-AMP) is a second messenger involved in diverse metabolic processes, including osmolyte uptake, cell wall homeostasis, and antibiotic and heat resistance. In Lactococcus lactis, a lactic acid bacterium which is used in the dairy industry and as a cell factory in biotechnological processes, the only reported interaction partners of c-di-AMP are the pyruvate carboxylase and BusR, the transcription regulator of the busAB operon for glycine betaine uptake. However, recent studies uncovered a major role of c-di-AMP in the control of potassium homeostasis, and potassium is the signal that triggers c-di-AMP synthesis. In this study, we have identified KupA and KupB, which belong to the Kup/HAK/KT family, as novel c-di-AMP binding proteins. Both proteins are high-affinity potassium transporters, and their transport activities are inhibited by binding of c-di-AMP. Thus, in addition to the well-studied Ktr/Trk potassium channels, KupA and KupB represent a second class of potassium transporters that are subject to inhibition by c-di-AMP.IMPORTANCE Potassium is an essential ion in every living cell. Even though potassium is the most abundant cation in cells, its accumulation can be toxic. Therefore, the level of potassium has to be tightly controlled. In many Gram-positive bacteria, the second messenger cyclic di-AMP plays a key role in the control of potassium homeostasis by binding to potassium transporters and regulatory proteins and RNA molecules. In the lactic acid bacterium Lactococcus lactis, none of these conserved c-di-AMP-responsive molecules are present. In this study, we demonstrate that the KupA and KupB proteins of L. lactis IL1403 are high-affinity potassium transporters and that their transport activity is inhibited by the second messenger c-di-AMP.
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15
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Asif MA, Schilling RK, Tilbrook J, Brien C, Dowling K, Rabie H, Short L, Trittermann C, Garcia A, Barrett-Lennard EG, Berger B, Mather DE, Gilliham M, Fleury D, Tester M, Roy SJ, Pearson AS. Mapping of novel salt tolerance QTL in an Excalibur × Kukri doubled haploid wheat population. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 2018; 131:2179-2196. [PMID: 30062653 PMCID: PMC6154029 DOI: 10.1007/s00122-018-3146-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Accepted: 07/14/2018] [Indexed: 05/04/2023]
Abstract
KEY MESSAGE Novel QTL for salinity tolerance traits have been detected using non-destructive and destructive phenotyping in bread wheat and were shown to be linked to improvements in yield in saline fields. Soil salinity is a major limitation to cereal production. Breeding new salt-tolerant cultivars has the potential to improve cereal crop yields. In this study, a doubled haploid bread wheat mapping population, derived from the bi-parental cross of Excalibur × Kukri, was grown in a glasshouse under control and salinity treatments and evaluated using high-throughput non-destructive imaging technology. Quantitative trait locus (QTL) analysis of this population detected multiple QTL under salt and control treatments. Of these, six QTL were detected in the salt treatment including one for maintenance of shoot growth under salinity (QG(1-5).asl-7A), one for leaf Na+ exclusion (QNa.asl-7A) and four for leaf K+ accumulation (QK.asl-2B.1, QK.asl-2B.2, QK.asl-5A and QK:Na.asl-6A). The beneficial allele for QG(1-5).asl-7A (the maintenance of shoot growth under salinity) was present in six out of 44 mainly Australian bread and durum wheat cultivars. The effect of each QTL allele on grain yield was tested in a range of salinity concentrations at three field sites across 2 years. In six out of nine field trials with different levels of salinity stress, lines with alleles for Na+ exclusion and/or K+ maintenance at three QTL (QNa.asl-7A, QK.asl-2B.2 and QK:Na.asl-6A) excluded more Na+ or accumulated more K+ compared to lines without these alleles. Importantly, the QK.asl-2B.2 allele for higher K+ accumulation was found to be associated with higher grain yield at all field sites. Several alleles at other QTL were associated with higher grain yields at selected field sites.
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Affiliation(s)
- Muhammad A Asif
- Australian Centre for Plant Functional Genomics, PMB 1, Glen Osmond, SA, 5064, Australia
- School of Agriculture, Food and Wine, The University of Adelaide, PMB 1, Glen Osmond, SA, 5064, Australia
| | - Rhiannon K Schilling
- Australian Centre for Plant Functional Genomics, PMB 1, Glen Osmond, SA, 5064, Australia
- School of Agriculture, Food and Wine, The University of Adelaide, PMB 1, Glen Osmond, SA, 5064, Australia
| | - Joanne Tilbrook
- Australian Centre for Plant Functional Genomics, PMB 1, Glen Osmond, SA, 5064, Australia
- School of Agriculture, Food and Wine, The University of Adelaide, PMB 1, Glen Osmond, SA, 5064, Australia
- Plant Industries Development, Department of Primary Industry and Resources, PO Box 3000, Darwin, NT, 0801, Australia
| | - Chris Brien
- Australian Centre for Plant Functional Genomics, PMB 1, Glen Osmond, SA, 5064, Australia
- The Plant Accelerator, Australian Plant Phenomics Facility, The University of Adelaide, Urrbrae, SA, 5064, Australia
- Phenomics and Bioinformatics Research Center, The University of South Australia, GPO Box 2471, Mawson Lakes, 5001, SA, Australia
| | - Kate Dowling
- Australian Centre for Plant Functional Genomics, PMB 1, Glen Osmond, SA, 5064, Australia
- The Plant Accelerator, Australian Plant Phenomics Facility, The University of Adelaide, Urrbrae, SA, 5064, Australia
| | - Huwaida Rabie
- Phenomics and Bioinformatics Research Center, The University of South Australia, GPO Box 2471, Mawson Lakes, 5001, SA, Australia
- Bethlehem University, Rue de Freres #9, Bethlehem, West Bank, Palestine
| | - Laura Short
- Australian Centre for Plant Functional Genomics, PMB 1, Glen Osmond, SA, 5064, Australia
- School of Agriculture, Food and Wine, The University of Adelaide, PMB 1, Glen Osmond, SA, 5064, Australia
| | - Christine Trittermann
- Australian Centre for Plant Functional Genomics, PMB 1, Glen Osmond, SA, 5064, Australia
- School of Agriculture, Food and Wine, The University of Adelaide, PMB 1, Glen Osmond, SA, 5064, Australia
| | - Alexandre Garcia
- Australian Centre for Plant Functional Genomics, PMB 1, Glen Osmond, SA, 5064, Australia
- School of Agriculture, Food and Wine, The University of Adelaide, PMB 1, Glen Osmond, SA, 5064, Australia
- The Plant Accelerator, Australian Plant Phenomics Facility, The University of Adelaide, Urrbrae, SA, 5064, Australia
| | - Edward G Barrett-Lennard
- School of Agriculture and Environment (M084), The University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia
- Department of Primary Industries and Regional Development, 3 Baron-Hay Court, South Perth, 6151, WA, Australia
| | - Bettina Berger
- School of Agriculture, Food and Wine, The University of Adelaide, PMB 1, Glen Osmond, SA, 5064, Australia
- The Plant Accelerator, Australian Plant Phenomics Facility, The University of Adelaide, Urrbrae, SA, 5064, Australia
| | - Diane E Mather
- School of Agriculture, Food and Wine, The University of Adelaide, PMB 1, Glen Osmond, SA, 5064, Australia
| | - Matthew Gilliham
- School of Agriculture, Food and Wine, The University of Adelaide, PMB 1, Glen Osmond, SA, 5064, Australia
- ARC Centre of Excellence in Plant Energy Biology, The University of Adelaide, PMB 1, Glen Osmond, SA, 5064, Australia
| | - Delphine Fleury
- Australian Centre for Plant Functional Genomics, PMB 1, Glen Osmond, SA, 5064, Australia
- School of Agriculture, Food and Wine, The University of Adelaide, PMB 1, Glen Osmond, SA, 5064, Australia
| | - Mark Tester
- Australian Centre for Plant Functional Genomics, PMB 1, Glen Osmond, SA, 5064, Australia
- School of Agriculture, Food and Wine, The University of Adelaide, PMB 1, Glen Osmond, SA, 5064, Australia
- Division of Biological and Environmental Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
| | - Stuart J Roy
- Australian Centre for Plant Functional Genomics, PMB 1, Glen Osmond, SA, 5064, Australia.
- School of Agriculture, Food and Wine, The University of Adelaide, PMB 1, Glen Osmond, SA, 5064, Australia.
| | - Allison S Pearson
- Australian Centre for Plant Functional Genomics, PMB 1, Glen Osmond, SA, 5064, Australia
- School of Agriculture, Food and Wine, The University of Adelaide, PMB 1, Glen Osmond, SA, 5064, Australia
- ARC Centre of Excellence in Plant Energy Biology, The University of Adelaide, PMB 1, Glen Osmond, SA, 5064, Australia
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Santa María GE, Oliferuk S, Moriconi JI. A survey of sequences of KT-HAK-KUP transporters in green algae and basal land plants. Data Brief 2018; 19:2356-2363. [PMID: 30238025 PMCID: PMC6144887 DOI: 10.1016/j.dib.2018.07.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Accepted: 07/05/2018] [Indexed: 11/29/2022] Open
Abstract
In this data article, information is provided on sequences of KT-HAK-KUP transporters from green algae and basal land plants. A data set is offered containing sequences corresponding to the chlorophyte algae Chlamydomonas eustigma, Gonium pectorale and Coccomyxa subellipsoidea, the charophyte algae Coleochaete orbicularis and Klebsormidium flaccidum, the bryophyte Sphagnum fallax, the marchantophyte Marchantia polymorpha and the gymnosperm Pinus taeda, which have been not formerly analyzed. In addition, an analysis of similarity scores among representatives of the clusters recognized in photosynthetic green organisms (namely, chlorophyte algae, charophyte algae, basal embryophytes and higher embryophytes) is performed as well as an analysis of membrane topology for them.
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Affiliation(s)
- Guillermo E Santa María
- Instituto Tecnológico Chascomús (INTECH), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Universidad Nacional de San Martín (UNSAM), Avda Intendente Marino km 8,2, Chascomús 7130, Provincia de Buenos Aires, Argentina
| | - Sonia Oliferuk
- Instituto Tecnológico Chascomús (INTECH), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Universidad Nacional de San Martín (UNSAM), Avda Intendente Marino km 8,2, Chascomús 7130, Provincia de Buenos Aires, Argentina
| | - Jorge I Moriconi
- Instituto Tecnológico Chascomús (INTECH), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Universidad Nacional de San Martín (UNSAM), Avda Intendente Marino km 8,2, Chascomús 7130, Provincia de Buenos Aires, Argentina
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17
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Santa-María GE, Oliferuk S, Moriconi JI. KT-HAK-KUP transporters in major terrestrial photosynthetic organisms: A twenty years tale. JOURNAL OF PLANT PHYSIOLOGY 2018; 226:77-90. [PMID: 29704646 DOI: 10.1016/j.jplph.2018.04.008] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2017] [Revised: 04/04/2018] [Accepted: 04/15/2018] [Indexed: 05/24/2023]
Abstract
Since their discovery, twenty years ago, KT-HAK-KUP transporters have become a keystone to understand how alkali cation fluxes are controlled in major land-dwelling photosynthetic organisms. In this review we focus on their discovery, phylogeny, and functions, as well as the regulation of its canonical member, AtHAK5. We also address issues related to structure-function studies, and the technological possibilities opened up by recent findings. Available evidence suggests that this family of transporters underwent an early divergence into major groups following the conquest of land by embryophytes. KT-HAK-KUPs are necessary to accomplish several major developmental and growth processes, as well as to ensure plant responses to environmental injuries. Although the primary function of these transporters is to mediate potassium (K+) fluxes, some of them can also mediate sodium (Na+) and cesium (Cs+) transport, and contribute to maintenance of K+ (and Na+) homeostasis in different plant tissues. In addition, there is evidence for a role of some members of this family in auxin movement and in adenylate cyclase activity. Recent research, focusing on the regulation of the canonical member of this family, AtHAK5, revealed the existence of a complex network that involves transcriptional and post-transcriptional phenomena which control the enhancement of AtHAK5-mediated K+ uptake when Arabidopsis thaliana plants are faced with low K+ supply. In spite of the formidable advances made since their discovery, important subjects remain to be elucidated to gain a more complete knowledge of the roles and regulation of KT-HAK-KUPs, as well as to improve their use for innovative procedures in crop breeding.
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Affiliation(s)
- Guillermo E Santa-María
- Instituto Tecnológico Chascomús (INTECH), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Universidad Nacional de San Martín (UNSAM), Avda Intendente Marino km 8, 2. Chascomús, 7130, Provincia de Buenos Aires, Argentina.
| | - Sonia Oliferuk
- Instituto Tecnológico Chascomús (INTECH), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Universidad Nacional de San Martín (UNSAM), Avda Intendente Marino km 8, 2. Chascomús, 7130, Provincia de Buenos Aires, Argentina
| | - Jorge I Moriconi
- Instituto Tecnológico Chascomús (INTECH), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Universidad Nacional de San Martín (UNSAM), Avda Intendente Marino km 8, 2. Chascomús, 7130, Provincia de Buenos Aires, Argentina
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18
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Tanudjaja E, Hoshi N, Su YH, Hamamoto S, Uozumi N. Kup-mediated Cs + uptake and Kdp-driven K + uptake coordinate to promote cell growth during excess Cs + conditions in Escherichia coli. Sci Rep 2017; 7:2122. [PMID: 28522840 PMCID: PMC5437092 DOI: 10.1038/s41598-017-02164-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Accepted: 04/07/2017] [Indexed: 01/05/2023] Open
Abstract
The physiological effects of caesium (Cs) on living cells are poorly understood. Here, we examined the physiological role of Cs+ on the activity of the potassium transporters in E. coli. In the absence of potassium (K+), Kup-mediated Cs+ uptake partially supported cell growth, however, at a much lower rate than with sufficient K+. In K+-limited medium (0.1 mM), the presence of Cs+ (up to 25 mM) in the medium enhanced growth as much as control medium containing 1 mM K+. This effect depended on the maintenance of basal levels of intracellular K+ by other K+ uptake transporters. Higher amounts of K+ (1 mM) in the medium eliminated the positive effect of Cs+ on growth, and revealed the inhibitory effect of high Cs+ on the growth of wild-type E. coli. Cells lacking Kdp, TrkG and TrkH but expressing Kup grew less well when Cs+ was increased in the medium. A kdp mutant contained an increased ratio of Cs+/K+ in the presence of high Cs+ in the medium and consequently was strongly inhibited in growth. Taken together, under excess Cs+ conditions Kup-mediated Cs+ influx sustains cell growth, which is supported by intracellular K+ supplied by Kdp.
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Affiliation(s)
- Ellen Tanudjaja
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aobayama 6-6-07, Sendai, 980-8579, Japan
| | - Naomi Hoshi
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aobayama 6-6-07, Sendai, 980-8579, Japan
| | - Yi-Hsin Su
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aobayama 6-6-07, Sendai, 980-8579, Japan
| | - Shin Hamamoto
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aobayama 6-6-07, Sendai, 980-8579, Japan
| | - Nobuyuki Uozumi
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aobayama 6-6-07, Sendai, 980-8579, Japan.
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19
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Ali MK, Li X, Tang Q, Liu X, Chen F, Xiao J, Ali M, Chou SH, He J. Regulation of Inducible Potassium Transporter KdpFABC by the KdpD/KdpE Two-Component System in Mycobacterium smegmatis. Front Microbiol 2017; 8:570. [PMID: 28484428 PMCID: PMC5401905 DOI: 10.3389/fmicb.2017.00570] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 03/20/2017] [Indexed: 12/28/2022] Open
Abstract
Kdp-ATPase is an inducible high affinity potassium uptake system that is widely distributed in bacteria, and is generally regulated by the KdpD/KdpE two-component system (TCS). In this study, conducted on Mycobacterium smegmatis, the kdpFABC (encoding Kdp-ATPase) expression was found to be affected by low concentration of K+, high concentrations of Na+, and/or [Formula: see text] of the medium. The KdpE was found to be a transcriptional regulator that bound to a specific 22-bp sequence in the promoter region of kdpFABC operon to positively regulate kdpFABC expression. The KdpE binding motif was highly conserved in the promoters of kdpFABC among the mycobacterial species. 5'-RACE data indicated a transcriptional start site (TSS) of the kdpFABC operon within the coding sequence of MSMEG_5391, which comprised a 120-bp long 5'-UTR and an open reading frame of the 87-bp kdpF gene. The kdpE deletion resulted in altered growth rate under normal and low K+ conditions. Furthermore, under K+ limiting conditions, a single transcript (kdpFABCDE) spanning kdpFABC and kdpDE operons was observed. This study provided the first insight into the regulation of kdpFABC operon by the KdpD/KdpE TCS in M. smegmatis.
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Affiliation(s)
- Maria K Ali
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural UniversityWuhan, China
| | - Xinfeng Li
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural UniversityWuhan, China
| | - Qing Tang
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural UniversityWuhan, China
| | - Xiaoyu Liu
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural UniversityWuhan, China
| | - Fang Chen
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural UniversityWuhan, China
| | - Jinfeng Xiao
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural UniversityWuhan, China
| | - Muhammad Ali
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural UniversityWuhan, China.,Biotechnology Program, Department of Environmental Sciences, COMSATS Institute of Information TechnologyAbbottabad, Pakistan
| | - Shan-Ho Chou
- Institute of Biochemistry and NCHU Agricultural Biotechnology Center, National Chung Hsing UniversityTaichung, Taiwan
| | - Jin He
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural UniversityWuhan, China
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20
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Durand A, Sinha AK, Dard-Dascot C, Michel B. Mutations Affecting Potassium Import Restore the Viability of the Escherichia coli DNA Polymerase III holD Mutant. PLoS Genet 2016; 12:e1006114. [PMID: 27280472 PMCID: PMC4900610 DOI: 10.1371/journal.pgen.1006114] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Accepted: 05/18/2016] [Indexed: 11/18/2022] Open
Abstract
Mutants lacking the ψ (HolD) subunit of the Escherichia coli DNA Polymerase III holoenzyme (Pol III HE) have poor viability, but a residual growth allows the isolation of spontaneous suppressor mutations that restore ΔholD mutant viability. Here we describe the isolation and characterization of two suppressor mutations in the trkA and trkE genes, involved in the main E. coli potassium import system. Viability of ΔholD trk mutants is abolished on media with low or high K+ concentrations, where alternative K+ import systems are activated, and is restored on low K+ concentrations by the inactivation of the alternative Kdp system. These findings show that the ΔholD mutant is rescued by a decrease in K+ import. The effect of trk inactivation is additive with the previously identified ΔholD suppressor mutation lexAind that blocks the SOS response indicating an SOS-independent mechanism of suppression. Accordingly, although lagging-strand synthesis is still perturbed in holD trkA mutants, the trkA mutation allows HolD-less Pol III HE to resist increased levels of the SOS-induced bypass polymerase DinB. trk inactivation is also partially additive with an ssb gene duplication, proposed to stabilize HolD-less Pol III HE by a modification of the single-stranded DNA binding protein (SSB) binding mode. We propose that lowering the intracellular K+ concentration stabilizes HolD-less Pol III HE on DNA by increasing electrostatic interactions between Pol III HE subunits, or between Pol III and DNA, directly or through a modification of the SSB binding mode; these three modes of action are not exclusive and could be additive. To our knowledge, the holD mutant provides the first example of an essential protein-DNA interaction that strongly depends on K+ import in vivo.
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Affiliation(s)
- Adeline Durand
- Genome biology department, Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette, France
| | - Anurag Kumar Sinha
- Genome biology department, Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette, France
| | - Cloelia Dard-Dascot
- High-throughput Sequencing facility, Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette, France
| | - Bénédicte Michel
- Genome biology department, Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette, France
- * E-mail:
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Elicharová H, Hušeková B, Sychrová H. ThreeCandida albicanspotassium uptake systems differ in their ability to provideSaccharomyces cerevisiae trk1trk2mutants with necessary potassium. FEMS Yeast Res 2016; 16:fow039. [DOI: 10.1093/femsyr/fow039] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/14/2016] [Indexed: 12/31/2022] Open
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Checchetto V, Segalla A, Sato Y, Bergantino E, Szabo I, Uozumi N. Involvement of Potassium Transport Systems in the Response of Synechocystis PCC 6803 Cyanobacteria to External pH Change, High-Intensity Light Stress and Heavy Metal Stress. PLANT & CELL PHYSIOLOGY 2016; 57:862-877. [PMID: 26880819 DOI: 10.1093/pcp/pcw032] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 02/04/2016] [Indexed: 06/05/2023]
Abstract
The unicellular photosynthetic cyanobacterium, able to survive in varying environments, is the only prokaryote that directly converts solar energy and CO2 into organic material and is thus relevant for primary production in many ecosystems. To maintain the intracellular and intrathylakoid ion homeostasis upon different environmental challenges, the concentration of potassium as a major intracellular cation has to be optimized by various K(+)uptake-mediated transport systems. We reveal here the specific and concerted physiological function of three K(+)transporters of the plasma and thylakoid membranes, namely of SynK (K(+)channel), KtrB (Ktr/Trk/HKT) and KdpA (Kdp) in Synechocystis sp. strain PCC 6803, under specific stress conditions. The behavior of the wild type, single, double and triple mutants was compared, revealing that only Synk contributes to heavy metal-induced stress, while only Ktr/Kdp is involved in osmotic and salt stress adaptation. With regards to pH shifts in the external medium, the Kdp/Ktr uptake systems play an important role in the adaptation to acidic pH. Ktr, by affecting the CO2 concentration mechanism via its action on the bicarbonate transporter SbtA, might also be responsible for the observed effects concerning high-light stress and calcification. In the case of illumination with high-intensity light, a synergistic action of Kdr/Ktp and SynK is required in order to avoid oxidative stress and ensure cell viability. In summary, this study dissects, using growth tests, measurement of photosynthetic activity and analysis of ultrastructure, the physiological role of three K(+)transporters in adaptation of the cyanobacteria to various environmental changes.
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Affiliation(s)
- Vanessa Checchetto
- Department of Biology, University of Padova, Padova 35121, Italy Department of Biomedical Sciences, University of Padova, Padova 35121, Italy
| | - Anna Segalla
- Department of Biology, University of Padova, Padova 35121, Italy
| | - Yuki Sato
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, 980-8579 Japan
| | | | - Ildiko Szabo
- Department of Biology, University of Padova, Padova 35121, Italy
| | - Nobuyuki Uozumi
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, 980-8579 Japan
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Han M, Wu W, Wu WH, Wang Y. Potassium Transporter KUP7 Is Involved in K(+) Acquisition and Translocation in Arabidopsis Root under K(+)-Limited Conditions. MOLECULAR PLANT 2016; 9:437-446. [PMID: 26851373 DOI: 10.1016/j.molp.2016.01.012] [Citation(s) in RCA: 93] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 01/05/2016] [Accepted: 01/28/2016] [Indexed: 05/17/2023]
Abstract
Potassium (K(+)) is one of the essential macronutrients for plant growth and development. K(+) uptake from environment and K(+) translocation in plants are conducted by K(+) channels and transporters. In this study, we demonstrated that KT/HAK/KUP transporter KUP7 plays crucial roles in K(+) uptake and translocation in Arabidopsis root. The kup7 mutant exhibited a sensitive phenotype on low-K(+) medium, whose leaves showed chlorosis symptoms compared with wild-type plants. Loss of function of KUP7 led to a reduction of K(+) uptake rate and K(+) content in xylem sap under K(+)-deficient conditions. Thus, the K(+) content in kup7 shoot was significantly reduced under low-K(+) conditions. Localization analysis revealed that KUP7 was predominantly targeted to the plasma membrane. The complementation assay in yeast suggested that KUP7 could mediate K(+) transport. In addition, phosphorylation on S80, S719, and S721 was important for KUP7 activity. KUP7 was ubiquitously expressed in many organs/tissues, and showed a higher expression level in Arabidopsis root. Together, our data demonstrated that KUP7 is crucial for K(+) uptake in Arabidopsis root and might be also involved in K(+) transport into xylem sap, affecting K(+) translocation from root toward shoot, especially under K(+)-limited conditions.
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Affiliation(s)
- Min Han
- State Key Laboratory of Plant Physiology and Biochemistry (SKLPPB), College of Biological Sciences, National Plant Gene Research Centre (Beijing), China Agricultural University, Beijing 100193, China
| | - Wei Wu
- State Key Laboratory of Plant Physiology and Biochemistry (SKLPPB), College of Biological Sciences, National Plant Gene Research Centre (Beijing), China Agricultural University, Beijing 100193, China
| | - Wei-Hua Wu
- State Key Laboratory of Plant Physiology and Biochemistry (SKLPPB), College of Biological Sciences, National Plant Gene Research Centre (Beijing), China Agricultural University, Beijing 100193, China
| | - Yi Wang
- State Key Laboratory of Plant Physiology and Biochemistry (SKLPPB), College of Biological Sciences, National Plant Gene Research Centre (Beijing), China Agricultural University, Beijing 100193, China.
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24
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Ruiz-Lau N, Bojórquez-Quintal E, Benito B, Echevarría-Machado I, Sánchez-Cach LA, Medina-Lara MDF, Martínez-Estévez M. Molecular Cloning and Functional Analysis of a Na +-Insensitive K + Transporter of Capsicum chinense Jacq. FRONTIERS IN PLANT SCIENCE 2016; 7:1980. [PMID: 28083010 PMCID: PMC5186809 DOI: 10.3389/fpls.2016.01980] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Accepted: 12/13/2016] [Indexed: 05/17/2023]
Abstract
High-affinity K+ (HAK) transporters are encoded by a large family of genes and are ubiquitous in the plant kingdom. These HAK-type transporters participate in low- and high-affinity potassium (K+) uptake and are crucial for the maintenance of K+ homeostasis under hostile conditions. In this study, the full-length cDNA of CcHAK1 gene was isolated from roots of the habanero pepper (Capsicum chinense). CcHAK1 expression was positively regulated by K+ starvation in roots and was not inhibited in the presence of NaCl. Phylogenetic analysis placed the CcHAK1 transporter in group I of the HAK K+ transporters, showing that it is closely related to Capsicum annuum CaHAK1 and Solanum lycopersicum LeHAK5. Characterization of the protein in a yeast mutant deficient in high-affinity K+ uptake (WΔ3) suggested that CcHAK1 function is associated with high-affinity K+ uptake, with Km and Vmax for Rb of 50 μM and 0.52 nmol mg-1 min-1, respectively. K+ uptake in yeast expressing the CcHAK1 transporter was inhibited by millimolar concentrations of the cations ammonium ([Formula: see text]) and cesium (Cs+) but not by sodium (Na+). The results presented in this study suggest that the CcHAK1 transporter may contribute to the maintenance of K+ homeostasis in root cells in C. chinense plants undergoing K+-deficiency and salt stress.
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Affiliation(s)
- Nancy Ruiz-Lau
- Unidad de Bioquímica y Biología Molecular de Plantas, Centro de Investigación Científica de YucatánMérida, Mexico
- CONACYT, Instituto Tecnológico Nacional de México, Instituto Tecnológico de Tuxtla GutiérrezTuxtla Gutiérrez, Mexico
| | - Emanuel Bojórquez-Quintal
- Unidad de Bioquímica y Biología Molecular de Plantas, Centro de Investigación Científica de YucatánMérida, Mexico
- CONACYT, Laboratorio de Análisis y Diagnóstico del Patrimonio, Colegio de MichoacánZamora, Mexico
| | - Begoña Benito
- Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de MadridMadrid, Spain
| | - Ileana Echevarría-Machado
- Unidad de Bioquímica y Biología Molecular de Plantas, Centro de Investigación Científica de YucatánMérida, Mexico
| | - Lucila A. Sánchez-Cach
- Unidad de Bioquímica y Biología Molecular de Plantas, Centro de Investigación Científica de YucatánMérida, Mexico
| | - María de Fátima Medina-Lara
- Unidad de Bioquímica y Biología Molecular de Plantas, Centro de Investigación Científica de YucatánMérida, Mexico
| | - Manuel Martínez-Estévez
- Unidad de Bioquímica y Biología Molecular de Plantas, Centro de Investigación Científica de YucatánMérida, Mexico
- *Correspondence: Manuel Martínez-Estévez
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Hamamoto S, Horie T, Hauser F, Deinlein U, Schroeder JI, Uozumi N. HKT transporters mediate salt stress resistance in plants: from structure and function to the field. Curr Opin Biotechnol 2015; 32:113-120. [DOI: 10.1016/j.copbio.2014.11.025] [Citation(s) in RCA: 110] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Accepted: 11/28/2014] [Indexed: 10/24/2022]
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26
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Large dsDNA chloroviruses encode diverse membrane transport proteins. Virology 2015; 479-480:38-45. [PMID: 25766639 DOI: 10.1016/j.virol.2015.02.025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Revised: 01/20/2015] [Accepted: 02/07/2015] [Indexed: 10/23/2022]
Abstract
Many large DNA viruses that infect certain isolates of chlorella-like green algae (chloroviruses) are unusual because they often encode a diverse set of membrane transport proteins, including functional K(+) channels and aquaglyceroporins as well as K(+) transporters and calcium transporting ATPases. Some chloroviruses also encode putative ligand-gated-like channel proteins. No one protein is present in all of the chloroviruses that have been sequenced, but the K(+) channel is the most common as only two chloroviruses have been isolated that lack this complete protein. This review describes the properties of these membrane-transporting proteins and suggests possible physiological functions and evolutionary histories for some of them.
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Rahn-Lee L, Byrne ME, Zhang M, Le Sage D, Glenn DR, Milbourne T, Walsworth RL, Vali H, Komeili A. A genetic strategy for probing the functional diversity of magnetosome formation. PLoS Genet 2015; 11:e1004811. [PMID: 25569806 PMCID: PMC4287615 DOI: 10.1371/journal.pgen.1004811] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Accepted: 10/07/2014] [Indexed: 11/18/2022] Open
Abstract
Model genetic systems are invaluable, but limit us to understanding only a few organisms in detail, missing the variations in biological processes that are performed by related organisms. One such diverse process is the formation of magnetosome organelles by magnetotactic bacteria. Studies of model magnetotactic α-proteobacteria have demonstrated that magnetosomes are cubo-octahedral magnetite crystals that are synthesized within pre-existing membrane compartments derived from the inner membrane and orchestrated by a specific set of genes encoded within a genomic island. However, this model cannot explain all magnetosome formation, which is phenotypically and genetically diverse. For example, Desulfovibrio magneticus RS-1, a δ-proteobacterium for which we lack genetic tools, produces tooth-shaped magnetite crystals that may or may not be encased by a membrane with a magnetosome gene island that diverges significantly from those of the α-proteobacteria. To probe the functional diversity of magnetosome formation, we used modern sequencing technology to identify hits in RS-1 mutated with UV or chemical mutagens. We isolated and characterized mutant alleles of 10 magnetosome genes in RS-1, 7 of which are not found in the α-proteobacterial models. These findings have implications for our understanding of magnetosome formation in general and demonstrate the feasibility of applying a modern genetic approach to an organism for which classic genetic tools are not available.
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Affiliation(s)
- Lilah Rahn-Lee
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California, United States of America
| | - Meghan E. Byrne
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California, United States of America
| | - Manjing Zhang
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California, United States of America
| | - David Le Sage
- Department of Physics, Harvard University, Cambridge, Massachusetts, United States of America
- Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, United States of America
| | - David R. Glenn
- Department of Physics, Harvard University, Cambridge, Massachusetts, United States of America
- Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, United States of America
- Center for Brain Science, Harvard University, Cambridge, Massachusetts, United States of America
| | - Timothy Milbourne
- Department of Physics, Harvard University, Cambridge, Massachusetts, United States of America
| | - Ronald L. Walsworth
- Department of Physics, Harvard University, Cambridge, Massachusetts, United States of America
- Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, United States of America
- Center for Brain Science, Harvard University, Cambridge, Massachusetts, United States of America
| | - Hojatollah Vali
- Facility for Electron Microscopy Research, McGill University, Montreal, Quebec, Canada
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada
- Department of Earth and Planetary Sciences, McGill University, Montreal, Quebec, Canada
| | - Arash Komeili
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California, United States of America
- * E-mail:
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28
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Comparative analysis of kdp and ktr mutants reveals distinct roles of the potassium transporters in the model cyanobacterium Synechocystis sp. strain PCC 6803. J Bacteriol 2014; 197:676-87. [PMID: 25313394 DOI: 10.1128/jb.02276-14] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Photoautotrophic bacteria have developed mechanisms to maintain K(+) homeostasis under conditions of changing ionic concentrations in the environment. Synechocystis sp. strain PCC 6803 contains genes encoding a well-characterized Ktr-type K(+) uptake transporter (Ktr) and a putative ATP-dependent transporter specific for K(+) (Kdp). The contributions of each of these K(+) transport systems to cellular K(+) homeostasis have not yet been defined conclusively. To verify the functionality of Kdp, kdp genes were expressed in Escherichia coli, where Kdp conferred K(+) uptake, albeit with lower rates than were conferred by Ktr. An on-chip microfluidic device enabled monitoring of the biphasic initial volume recovery of single Synechocystis cells after hyperosmotic shock. Here, Ktr functioned as the primary K(+) uptake system during the first recovery phase, whereas Kdp did not contribute significantly. The expression of the kdp operon in Synechocystis was induced by extracellular K(+) depletion. Correspondingly, Kdp-mediated K(+) uptake supported Synechocystis cell growth with trace amounts of external potassium. This induction of kdp expression depended on two adjacent genes, hik20 and rre19, encoding a putative two-component system. The circadian expression of kdp and ktr peaked at subjective dawn, which may support the acquisition of K(+) required for the regular diurnal photosynthetic metabolism. These results indicate that Kdp contributes to the maintenance of a basal intracellular K(+) concentration under conditions of limited K(+) in natural environments, whereas Ktr mediates fast potassium movements in the presence of greater K(+) availability. Through their distinct activities, both Ktr and Kdp coordinate the responses of Synechocystis to changes in K(+) levels under fluctuating environmental conditions.
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Alemán F, Caballero F, Ródenas R, Rivero RM, Martínez V, Rubio F. The F130S point mutation in the Arabidopsis high-affinity K(+) transporter AtHAK5 increases K(+) over Na(+) and Cs(+) selectivity and confers Na(+) and Cs(+) tolerance to yeast under heterologous expression. FRONTIERS IN PLANT SCIENCE 2014; 5:430. [PMID: 25228905 PMCID: PMC4151339 DOI: 10.3389/fpls.2014.00430] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Accepted: 08/13/2014] [Indexed: 05/20/2023]
Abstract
Potassium (K(+)) is an essential macronutrient required for plant growth, development and high yield production of crops. Members of group I of the KT/HAK/KUP family of transporters, such as HAK5, are key components for K(+) acquisition by plant roots at low external K(+) concentrations. Certain abiotic stress conditions such as salinity or Cs(+)-polluted soils may jeopardize plant K(+) nutrition because HAK5-mediated K(+) transport is inhibited by Na(+) and Cs(+). Here, by screening in yeast a randomly-mutated collection of AtHAK5 transporters, a new mutation in AtHAK5 sequence is identified that greatly increases Na(+) tolerance. The single point mutation F130S, affecting an amino acid residue conserved in HAK5 transporters from several species, confers high salt tolerance, as well as Cs(+) tolerance. This mutation increases more than 100-fold the affinity of AtHAK5 for K(+) and reduces the K i values for Na(+) and Cs(+), suggesting that the F130 residue may contribute to the structure of the pore region involved in K(+) binding. In addition, this mutation increases the V max for K(+). All this changes occur without increasing the amount of the AtHAK5 protein in yeast and support the idea that this residue is contributing to shape the selectivity filter of the AtHAK5 transporter.
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Affiliation(s)
| | | | | | | | | | - Francisco Rubio
- *Correspondence: Francisco Rubio, Centro de Edafología y Biología Aplicada del Segura-CSIC, Campus de Espinardo, 30100 Murcia, Spain e-mail:
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