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Gao S, Yang Y, Guo J, Zhang X, Feng M, Su Y, Que Y, Xu L. Ectopic Expression of Sugarcane ScAMT1.1 Has the Potential to Improve Ammonium Assimilation and Grain Yield in Transgenic Rice under Low Nitrogen Stress. Int J Mol Sci 2023; 24:ijms24021595. [PMID: 36675108 PMCID: PMC9863325 DOI: 10.3390/ijms24021595] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 01/02/2023] [Accepted: 01/04/2023] [Indexed: 01/15/2023] Open
Abstract
In China, nitrogen (N) fertilizer is excessively used in sugarcane planting areas, while the nitrogen use efficiency (NUE) of sugarcane is relatively low. Mining and identifying the key genes in response to low N stress in sugarcane can provide useful gene elements and a theoretical basis for developing sugarcane varieties with high NUE. In our study, RNA-Seq combined with qRT-PCR analysis revealed that the ScAMT1.1 gene responded positively to low N stress, resulting in the stronger low N tolerance and high NUE ability of sugarcane cultivar ROC22. Then, ScAMT1.1 was cloned from sugarcane. The full-length cDNA of the ScAMT1.1 gene is 1868 bp, containing a 1491 bp open reading frame (ORF), and encoding 496 amino acids. ScAMT1.1 belongs to the AMT superfamily and shares 91.57% homologies with AMT1.1 from Oryza sativa. Furthermore, it was stably overexpressed in rice (O. sativa). Under low N treatment, the plant height and the fresh weight of the ScAMT1.1-overexpressed transgenic rice were 36.48% and 51.55% higher than that of the wild-type, respectively. Both the activity of ammonium assimilation key enzymes GS and GDH, and the expression level of ammonium assimilation key genes, including GS1.1, GS1.2, GDH, Fd-GOGAT, and NADH-GOGAT2 in the transgenic plants, were significantly higher than that of the wild-type. The grain number and grain yield per plant in the transgenic rice were 6.44% and 9.52% higher than that of the wild-type in the pot experiments, respectively. Taken together, the sugarcane ScAMT1.1 gene has the potential to improve ammonium assimilation ability and the yield of transgenic rice under low N fertilizer conditions. This study provided an important functional gene for improving sugarcane varieties with high NUE.
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Affiliation(s)
| | - Yingying Yang
- Correspondence: (Y.Y.); (L.X.); Tel.: +86-591-8385-1742 (Y.Y. & L.X.)
| | | | | | | | | | | | - Liping Xu
- Correspondence: (Y.Y.); (L.X.); Tel.: +86-591-8385-1742 (Y.Y. & L.X.)
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Hui J, An X, Li Z, Neuhäuser B, Ludewig U, Wu X, Schulze WX, Chen F, Feng G, Lambers H, Zhang F, Yuan L. The mycorrhiza-specific ammonium transporter ZmAMT3;1 mediates mycorrhiza-dependent nitrogen uptake in maize roots. THE PLANT CELL 2022; 34:4066-4087. [PMID: 35880836 PMCID: PMC9516061 DOI: 10.1093/plcell/koac225] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Accepted: 06/18/2022] [Indexed: 06/15/2023]
Abstract
Most plant species can form symbioses with arbuscular mycorrhizal fungi (AMFs), which may enhance the host plant's acquisition of soil nutrients. In contrast to phosphorus nutrition, the molecular mechanism of mycorrhizal nitrogen (N) uptake remains largely unknown, and its physiological relevance is unclear. Here, we identified a gene encoding an AMF-inducible ammonium transporter, ZmAMT3;1, in maize (Zea mays) roots. ZmAMT3;1 was specifically expressed in arbuscule-containing cortical cells and the encoded protein was localized at the peri-arbuscular membrane. Functional analysis in yeast and Xenopus oocytes indicated that ZmAMT3;1 mediated high-affinity ammonium transport, with the substrate NH4+ being accessed, but likely translocating uncharged NH3. Phosphorylation of ZmAMT3;1 at the C-terminus suppressed transport activity. Using ZmAMT3;1-RNAi transgenic maize lines grown in compartmented pot experiments, we demonstrated that substantial quantities of N were transferred from AMF to plants, and 68%-74% of this capacity was conferred by ZmAMT3;1. Under field conditions, the ZmAMT3;1-dependent mycorrhizal N pathway contributed >30% of postsilking N uptake. Furthermore, AMFs downregulated ZmAMT1;1a and ZmAMT1;3 protein abundance and transport activities expressed in the root epidermis, suggesting a trade-off between mycorrhizal and direct root N-uptake pathways. Taken together, our results provide a comprehensive understanding of mycorrhiza-dependent N uptake in maize and present a promising approach to improve N-acquisition efficiency via plant-microbe interactions.
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Affiliation(s)
- Jing Hui
- College of Resources and Environmental Sciences, National Academy of Agriculture Green Development, Key Laboratory of Plant-Soil Interactions, MOE, China Agricultural University, Beijing, 100193, China
| | - Xia An
- College of Resources and Environmental Sciences, National Academy of Agriculture Green Development, Key Laboratory of Plant-Soil Interactions, MOE, China Agricultural University, Beijing, 100193, China
| | - Zhibo Li
- College of Resources and Environmental Sciences, National Academy of Agriculture Green Development, Key Laboratory of Plant-Soil Interactions, MOE, China Agricultural University, Beijing, 100193, China
| | - Benjamin Neuhäuser
- Department of Nutritional Crop Physiology, Institute of Crop Science, University of Hohenheim, Stuttgart, 70593, Germany
| | - Uwe Ludewig
- Department of Nutritional Crop Physiology, Institute of Crop Science, University of Hohenheim, Stuttgart, 70593, Germany
| | - Xuna Wu
- Department of Plant Systems Biology, Institute for Physiology and Biotechnology of Plants, University of Hohenheim, Stuttgart, 70593, Germany
| | - Waltraud X Schulze
- Department of Plant Systems Biology, Institute for Physiology and Biotechnology of Plants, University of Hohenheim, Stuttgart, 70593, Germany
| | - Fanjun Chen
- College of Resources and Environmental Sciences, National Academy of Agriculture Green Development, Key Laboratory of Plant-Soil Interactions, MOE, China Agricultural University, Beijing, 100193, China
| | - Gu Feng
- College of Resources and Environmental Sciences, National Academy of Agriculture Green Development, Key Laboratory of Plant-Soil Interactions, MOE, China Agricultural University, Beijing, 100193, China
| | - Hans Lambers
- School of Biological Science and Institute of Agriculture, University of Western Australia, Perth, WA6009, Australia
| | - Fusuo Zhang
- College of Resources and Environmental Sciences, National Academy of Agriculture Green Development, Key Laboratory of Plant-Soil Interactions, MOE, China Agricultural University, Beijing, 100193, China
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Bouteau F, Grésillon E, Chartier D, Arbelet-Bonnin D, Kawano T, Baluška F, Mancuso S, Calvo P, Laurenti P. Our sisters the plants? notes from phylogenetics and botany on plant kinship blindness. PLANT SIGNALING & BEHAVIOR 2021; 16:2004769. [PMID: 34913409 PMCID: PMC9208782 DOI: 10.1080/15592324.2021.2004769] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 07/13/2021] [Accepted: 11/08/2021] [Indexed: 05/27/2023]
Abstract
Before the upheaval brought about by phylogenetic classification, classical taxonomy separated living beings into two distinct kingdoms, animals and plants. Rooted in 'naturalist' cosmology, Western science has built its theoretical apparatus on this dichotomy mostly based on ancient Aristotelian ideas. Nowadays, despite the adoption of the Darwinian paradigm that unifies living organisms as a kinship, the concept of the "scale of beings" continues to structure our analysis and understanding of living species. Our aim is to combine developments in phylogeny, recent advances in biology, and renewed interest in plant agency to craft an interdisciplinary stance on the living realm. The lines at the origin of plant or animal have a common evolutionary history dating back to about 3.9 Ga, separating only 1.6 Ga ago. From a phylogenetic perspective of living species history, plants and animals belong to sister groups. With recent data related to the field of Plant Neurobiology, our aim is to discuss some socio-cultural obstacles, mainly in Western naturalist epistemology, that have prevented the integration of living organisms as relatives, while suggesting a few avenues inspired by practices principally from other ontologies that could help overcome these obstacles and build bridges between different ways of connecting to life.
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Affiliation(s)
- François Bouteau
- Laboratoire Interdisciplinaire Des Énergies de Demain, Université de Paris, France
| | - Etienne Grésillon
- Laboratoire Dynamiques Sociales Et Recomposition Des Espaces (Ladyss-umr 7533), Université de Paris, Paris, France
| | - Denis Chartier
- Laboratoire Dynamiques Sociales Et Recomposition Des Espaces (Ladyss-umr 7533), Université de Paris, Paris, France
| | | | - Tomonori Kawano
- Graduate School of Environmental Engineering, University of Kitakyushu 1–1, KitakyushuJapan
| | - František Baluška
- Institute of Cellular and Molecular Botany, University of Bonn, Bonn, Germany
| | - Stefano Mancuso
- LINV-DiSPAA, Department of Agri-Food and Environmental Science, University of Florence, Sesto Fiorentino (FI), Italy
| | - Paco Calvo
- Minimal Intelligence Lab, Department of Philosophy, University of Murcia, Murcia, Spain
| | - Patrick Laurenti
- Laboratoire Interdisciplinaire Des Énergies de Demain, Université de Paris, France
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Perin G, Fletcher T, Sagi-Kiss V, Gaboriau DCA, Carey MR, Bundy JG, Jones PR. Calm on the surface, dynamic on the inside. Molecular homeostasis of Anabaena sp. PCC 7120 nitrogen metabolism. PLANT, CELL & ENVIRONMENT 2021; 44:1885-1907. [PMID: 33608943 DOI: 10.1111/pce.14034] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 02/12/2021] [Accepted: 02/13/2021] [Indexed: 06/12/2023]
Abstract
Nitrogen sources are all converted into ammonium/ia as a first step of assimilation. It is reasonable to expect that molecular components involved in the transport of ammonium/ia across biological membranes connect with the regulation of both nitrogen and central metabolism. We applied both genetic (i.e., Δamt mutation) and environmental treatments to a target biological system, the cyanobacterium Anabaena sp PCC 7120. The aim was to both perturb nitrogen metabolism and induce multiple inner nitrogen states, respectively, followed by targeted quantification of key proteins, metabolites and enzyme activities. The absence of AMT transporters triggered a substantial whole-system response, affecting enzyme activities and quantity of proteins and metabolites, spanning nitrogen and carbon metabolisms. Moreover, the Δamt strain displayed a molecular fingerprint indicating nitrogen deficiency even under nitrogen replete conditions. Contrasting with such dynamic adaptations was the striking near-complete lack of an externally measurable altered phenotype. We conclude that this species evolved a highly robust and adaptable molecular network to maintain homeostasis, resulting in substantial internal but minimal external perturbations. This analysis provides evidence for a potential role of AMT transporters in the regulatory/signalling network of nitrogen metabolism and the existence of a novel fourth regulatory mechanism controlling glutamine synthetase activity.
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Affiliation(s)
- Giorgio Perin
- Department of Life Sciences, Imperial College London, London, UK
| | - Tyler Fletcher
- Complex Carbohydrate Research Center and Department of Chemistry, University of Georgia, Athens, Georgia, USA
| | - Virag Sagi-Kiss
- Department of Metabolism, Digestion and Reproduction, Imperial College London, London, UK
| | - David C A Gaboriau
- Facility for Imaging by Light Microscopy, NHLI, Imperial College London, London, UK
| | - Mathew R Carey
- Department of Metabolism, Digestion and Reproduction, Imperial College London, London, UK
| | - Jacob G Bundy
- Department of Metabolism, Digestion and Reproduction, Imperial College London, London, UK
| | - Patrik R Jones
- Department of Life Sciences, Imperial College London, London, UK
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Abstract
AbstractIt is crucial for the growth and development of an organism whether ammonium is transported across its membranes in a form of NH4+ or NH3. The transport of both molecules follows different pH-dependent gradients across membranes and transport of both substrates differentially affects the internal and external pH. As a consequence, they directly influence the physiology and organism development. CaMep2 from Candida albicans shows a dual transceptor function in ammonium transport and sensing. CaMep2 senses low ammonium availability and induces filamentous growth. CaMep1, by contrast, is only active in transport, but not involved in ammonium signaling. Here, both proteins were heterologously expressed in Xenopus laevis oocytes. This study identified electrogenic NH4+ transport by CaMep1 and electroneutral NH3 transport by CaMep2, which might be a prerequisite for the induction of pseudohyphal growth.
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Narayana R, Fliegmann J, Paponov I, Maffei ME. Reduction of geomagnetic field (GMF) to near null magnetic field (NNMF) affects Arabidopsis thaliana root mineral nutrition. LIFE SCIENCES IN SPACE RESEARCH 2018; 19:43-50. [PMID: 30482280 DOI: 10.1016/j.lssr.2018.08.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Revised: 08/28/2018] [Accepted: 08/30/2018] [Indexed: 05/20/2023]
Abstract
The Earth magnetic field (or geomagnetic field, GMF) is a natural component of our planet and variations of the GMF are perceived by plants with a still uncharacterized magnetoreceptor. The purpose of this work was to assess the effect of near null magnetic field (NNMF, ∼40 nT) on Arabidopsis thaliana Col0 root ion modulation. A time-course (from 10 min to 96 h) exposure of Arabidopsis to NNMF was compared to GMF and the content of some cations (NH4+, K+, Ca2+ and Mg2+) and anions (Cl-, SO4=, NO3- and PO4=) was evaluated by capillary electrophoresis. The expression of several cation and anion channel- and transporter-related genes was assessed by gene microarray. A few minutes after exposure to NNMF, Arabidopsis roots responded with a significant change in the content and gene expression of all nutrient ions under study, indicating the presence of a plant magnetoreceptor that responds immediately to MF variations by modulating channels, transporters and genes involved in mineral nutrition. The response of Arabidopsis to reduced MF was a general reduction of plant ion uptake and transport. Our data suggest the importance to understand the nature and function of the plant magnetoreceptor for future space programs involving plant growth in environments with a reduced MF.
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Affiliation(s)
- Ravishankar Narayana
- Department of Entomology, Penn State University, W249 Millennium Science Complex, University Park, PA 16802, USA
| | - Judith Fliegmann
- ZMBP Center for Plant Molecular Biology, University of Tübingen, Tübingen, Germany
| | - Ivan Paponov
- Norwegian Institute of Bioeconomy Research, Dept. of Fruit and Vegetables, Ås, Norway
| | - Massimo E Maffei
- Plant Physiology Unit, Department of Life Sciences and Systems Biology, University of Turin, Turin, Italy.
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Li H, Yang QS, Liu W, Lin J, Chang YH. The AMT1 family genes from Malus robusta display differential transcription features and ammonium transport abilities. Mol Biol Rep 2017; 44:379-390. [PMID: 28840433 DOI: 10.1007/s11033-017-4119-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2016] [Accepted: 08/19/2017] [Indexed: 11/28/2022]
Abstract
Ammonium is an important nitrogen sources for plant growth. In this study, we report on the gene characterization of the ammonium transporter AMT1 subfamily in the apple rootstock Malus robusta Rehd. Thirteen AMT genes were comprehensively evaluated from the apple genome (version 1.0). Then the gene features and expression patterns of five AMT1 members from M. robusta were analyzed. These genes fell into four clusters in the AMT phylogenetic tree: clade I (MrAMT1;1 and MrAMT1;3), clade II (MrAMT1;4), clade III (MrAMT1;2), and clade IV (MrAMT1;5). All the AMT1s, apart from MrAMT1;4, were expressed in vegetative organs and strongly responded to nitrogen concentration changes. For example, MrAMT1;2 and MrAMT1;3 had high transcript accumulation levels in the leaves and roots, respectively. Finally, the functions of these AMT1s were studied in detail by heterologous expression in yeast. These genes allowed strain 31019b to assimilate nitrogen, but their 15NH4+ uptake kinetics varied. These results revealed the functional roles of AMT1 during ammonium absorption in the AMT-defective mutant yeast system.
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Affiliation(s)
- Hui Li
- Institute of Horticulture, Jiangsu Academy of Agricultural Sciences/Jiangsu Key Laboratory for Horticultural Crop Genetic Improvement, Nanjing, China
| | - Qing-Song Yang
- Institute of Horticulture, Jiangsu Academy of Agricultural Sciences/Jiangsu Key Laboratory for Horticultural Crop Genetic Improvement, Nanjing, China
| | - Wei Liu
- Institute of Horticulture, Jiangsu Academy of Agricultural Sciences/Jiangsu Key Laboratory for Horticultural Crop Genetic Improvement, Nanjing, China
| | - Jing Lin
- Institute of Horticulture, Jiangsu Academy of Agricultural Sciences/Jiangsu Key Laboratory for Horticultural Crop Genetic Improvement, Nanjing, China
| | - You-Hong Chang
- Institute of Horticulture, Jiangsu Academy of Agricultural Sciences/Jiangsu Key Laboratory for Horticultural Crop Genetic Improvement, Nanjing, China.
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An JP, Qu FJ, Yao JF, Wang XN, You CX, Wang XF, Hao YJ. The bZIP transcription factor MdHY5 regulates anthocyanin accumulation and nitrate assimilation in apple. HORTICULTURE RESEARCH 2017; 4:17023. [PMID: 28611922 PMCID: PMC5461414 DOI: 10.1038/hortres.2017.23] [Citation(s) in RCA: 172] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Revised: 04/17/2017] [Accepted: 04/21/2017] [Indexed: 05/18/2023]
Abstract
The basic leucine zipper (bZIP) transcription factor HY5 plays a multifaceted role in plant growth and development. Here the apple MdHY5 gene was cloned based on its homology with Arabidopsis HY5. Expression analysis demonstrated that MdHY5 transcription was induced by light and abscisic acid treatments. Electrophoretic mobility shift assays and transient expression assays subsequently showed that MdHY5 positively regulated both its own transcription and that of MdMYB10 by binding to E-box and G-box motifs, respectively. Furthermore, we obtained transgenic apple calli that overexpressed the MdHY5 gene, and apple calli coloration assays showed that MdHY5 promoted anthocyanin accumulation by regulating expression of the MdMYB10 gene and downstream anthocyanin biosynthesis genes. In addition, the transcript levels of a series of nitrate reductase genes and nitrate uptake genes in both wild-type and transgenic apple calli were detected. In association with increased nitrate reductase activities and nitrate contents, the results indicated that MdHY5 might be an important regulator in nutrient assimilation. Taken together, these results indicate that MdHY5 plays a vital role in anthocyanin accumulation and nitrate assimilation in apple.
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Affiliation(s)
- Jian-Ping An
- National Key Laboratory of Crop Biology, MOA Key Laboratory of Horticultural Crop Biology and Germplasm Innovation, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai’An 271018, Shandong, China
| | - Feng-Jia Qu
- National Key Laboratory of Crop Biology, MOA Key Laboratory of Horticultural Crop Biology and Germplasm Innovation, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai’An 271018, Shandong, China
| | - Ji-Fang Yao
- National Key Laboratory of Crop Biology, MOA Key Laboratory of Horticultural Crop Biology and Germplasm Innovation, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai’An 271018, Shandong, China
| | - Xiao-Na Wang
- College of Life Science, Shandong Agricultural University, Tai’An 271018, Shandong, China
| | - Chun-Xiang You
- National Key Laboratory of Crop Biology, MOA Key Laboratory of Horticultural Crop Biology and Germplasm Innovation, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai’An 271018, Shandong, China
| | - Xiao-Fei Wang
- National Key Laboratory of Crop Biology, MOA Key Laboratory of Horticultural Crop Biology and Germplasm Innovation, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai’An 271018, Shandong, China
- ()
| | - Yu-Jin Hao
- National Key Laboratory of Crop Biology, MOA Key Laboratory of Horticultural Crop Biology and Germplasm Innovation, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai’An 271018, Shandong, China
- ()
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Li H, Han JL, Chang YH, Lin J, Yang QS. Gene characterization and transcription analysis of two new ammonium transporters in pear rootstock (Pyrus betulaefolia). JOURNAL OF PLANT RESEARCH 2016; 129:737-748. [PMID: 26943161 DOI: 10.1007/s10265-016-0799-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 10/29/2015] [Indexed: 05/07/2023]
Abstract
Ammonium is the primarily nitrogen source for plant growth, but the molecular basis of ammonium acquisition in fruit species remains poorly understood. In this study, we report on the characterization of two new ammonium transporters (AMT) in the perennial tree Pyrus betulaefolia. In silico analyses and yeast complementation assays revealed that both PbAMT1;3 and PbAMT1;5 can be classified in the AMT1 sub-family. The specific expression of PbAMT1;3 in roots and of PbAMT1;5 in leaves indicates that they have diverse functions in ammonium uptake or transport in P. betulaefolia. Their expression was strongly influenced by ammonium availability. In addition, the transcript level of PbAMT1;5 was significantly affected by the diurnal cycle and senescence hormones. They conferred the ability to uptake nitrogen to the yeast strain 31019b; however, the (15)NH4 (+) uptake kinetics of PbAMT1;3 were different from those of PbAMT1;5. Indeed, PbAMT1;3 had a higher affinity for (15)NH4 (+), and pH changes were associated with this substrates' transport in yeast. The present study provides basic gene features and transcriptional information for the two new members of the AMT1 sub-family in P. betulaefolia and will aid in decoding the precise roles of AMTs in P. betulaefolia physiology.
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Affiliation(s)
- Hui Li
- Institute of Horticulture, Jiangsu Academy of Agricultural Sciences/Jiangsu Key Laboratory for Horticultural Crop Genetic Improvement, No. 50 Zhongling Street, Nanjing, 210014, Jiangsu, China
| | - Jin-Long Han
- Institute of Horticulture, Jiangsu Academy of Agricultural Sciences/Jiangsu Key Laboratory for Horticultural Crop Genetic Improvement, No. 50 Zhongling Street, Nanjing, 210014, Jiangsu, China
| | - You-Hong Chang
- Institute of Horticulture, Jiangsu Academy of Agricultural Sciences/Jiangsu Key Laboratory for Horticultural Crop Genetic Improvement, No. 50 Zhongling Street, Nanjing, 210014, Jiangsu, China.
| | - Jing Lin
- Institute of Horticulture, Jiangsu Academy of Agricultural Sciences/Jiangsu Key Laboratory for Horticultural Crop Genetic Improvement, No. 50 Zhongling Street, Nanjing, 210014, Jiangsu, China
| | - Qing-Song Yang
- Institute of Horticulture, Jiangsu Academy of Agricultural Sciences/Jiangsu Key Laboratory for Horticultural Crop Genetic Improvement, No. 50 Zhongling Street, Nanjing, 210014, Jiangsu, China
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Boeckstaens M. [From the discovery of microbial Mep-Amt ammonium transporters to human Rhesus factors]. Med Sci (Paris) 2016; 32:394-400. [PMID: 27137697 DOI: 10.1051/medsci/20163204018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Ammonium, ubiquitous on Earth, plays major and distinct roles in most organisms. While it can be a nitrogen source for many microorganisms and plants, it is a cytotoxic metabolic product actively detoxified by the liver in animals. Furthermore, in the latter, ammonium synthesis in the kidney is involved in acid/base homeostasis. Ammonium transport is ensured by a family of proteins, called Mep-Amt-Rh. This family is conserved in all domains of life and comprises the human Rh factors, notably known in transfusional medicine. While the study of bacterial, fungal and vegetal Mep-Amt transporters reveals a fine-tuned and rapid regulation of these proteins in function of environmental changes, the regulation of animal Rh proteins has been poorly addressed. This review notably highlights the importance of the yeast model in the study of the regulation of these proteins as well as in the functional characterization of Mep-Amt-Rh members of diverse origins.
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Affiliation(s)
- Mélanie Boeckstaens
- Laboratoire de biologie du transport membranaire, IBMM, université Libre de Bruxelles, 12, rue des Professeurs Jeener et Brachet, 6041 Gosselies, Belgique
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Neuhäuser B, Dynowski M, Ludewig U. Switching substrate specificity of AMT/MEP/ Rh proteins. Channels (Austin) 2015; 8:496-502. [PMID: 25483282 DOI: 10.4161/19336950.2014.967618] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
In organisms from all kingdoms of life, ammonia and its conjugated ion ammonium are transported across membranes by proteins of the AMT/Rh family. Efficient and successful growth often depends on sufficient ammonium nutrition. The proteins mediating this transport, the so called Ammonium Transporter (AMT) or Rhesus like (Rh) proteins, share a very similar trimeric overall structure and a high sequence similarity even throughout the kingdoms. Even though structural components of the transport mechanism, like an external substrate recruitment site, an essential twin histidine pore motif, a phenylalanine gate and the hydrophobic pore are strongly conserved and have been analyzed in detail by molecular dynamic simulations and mutational studies, the substrate(s), which pass the central pores of the AMT/Rh subunits, NH4(+), NH3 + H(+), NH4(+) + H(+) or NH3, are still a matter of debate for most proteins, including the best characterized AmtB protein from Escherichia coli. The lack of a robust expression system for functional analysis has hampered proof of structural and mutational studies, although the NH3 transport function for Rh-like proteins is rarely disputed. In plant transporters belonging to the subfamily AMT1, transport is associated with electrical currents, while some plant transporters, notably of the AMT2 type, were suggested to transport NH3 across the membrane, without associated ionic currents. Here we summarize data in favor of each substrate for the distinct AMT/Rh classes, discuss mutants and how they differ in structure and functionality. A common mechanism with deprotonation and subsequent NH3 transport through the central subunit pore is suggested.
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Affiliation(s)
- Benjamin Neuhäuser
- a Institute of Crop Science; Nutritional Crop Physiology ; University of Hohenheim ; Stuttgart , Germany
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Neuhäuser B, Ludewig U. Uncoupling of ionic currents from substrate transport in the plant ammonium transporter AtAMT1;2. J Biol Chem 2014; 289:11650-11655. [PMID: 24634212 PMCID: PMC4002075 DOI: 10.1074/jbc.c114.552802] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Revised: 03/13/2014] [Indexed: 12/20/2022] Open
Abstract
The ammonium flux across prokaryotic, plant, and animal membranes is regulated by structurally related ammonium transporters (AMT) and/or related Rhesus (Rh) glycoproteins. Several plant AMT homologs, such as AtAMT1;2 from Arabidopsis, elicit ionic, ammonium-dependent currents when expressed in oocytes. By contrast, functional evidence for the transport of NH3 and the lack of coupled ionic currents has been provided for many Rh proteins. Furthermore, despite high resolution structures the transported substrate in many bacterial homologs, such as AmtB from Escherichia coli, is still unclear. In a heterologous genetic screen in yeast, AtAMT1;2 mutants with reduced transport activity were identified based on the resistance of yeast to the toxic transport analog methylamine. When expressed in oocytes, the reduced transport capacity was confirmed for either of the mutants Q67K, M72I,and W145S. Structural alignments suggest that these mutations were dispersed at subunit contact sites of trimeric AMTs, without direct contact to the pore lumen. Surprisingly, and in contrast to the wild type AtAMT1;2 transporter, ionic currents were not associated with the substrate transport in these mutants. Whether these data suggest that the wild type AtAMT1;2 functions as H(+)/NH3 co-transporter, as well as how the strict substrate coupling with protons is lost by the mutations, is discussed.
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Affiliation(s)
- Benjamin Neuhäuser
- Institute of Crop Science, Nutritional Crop Physiology, University of Hohenheim, Fruwirthstrasse 20, D-70593 Stuttgart, Germany.
| | - Uwe Ludewig
- Institute of Crop Science, Nutritional Crop Physiology, University of Hohenheim, Fruwirthstrasse 20, D-70593 Stuttgart, Germany
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Wang J, Fulford T, Shao Q, Javelle A, Yang H, Zhu W, Merrick M. Ammonium transport proteins with changes in one of the conserved pore histidines have different performance in ammonia and methylamine conduction. PLoS One 2013; 8:e62745. [PMID: 23667517 PMCID: PMC3647058 DOI: 10.1371/journal.pone.0062745] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 03/25/2013] [Indexed: 01/02/2023] Open
Abstract
Two conserved histidine residues are located near the mid-point of the conduction channel of ammonium transport proteins. The role of these histidines in ammonia and methylamine transport was evaluated by using a combination of in vivo studies, molecular dynamics (MD) simulation, and potential of mean force (PMF) calculations. Our in vivo results showed that a single change of either of the conserved histidines to alanine leads to the failure to transport methylamine but still facilitates good growth on ammonia, whereas double histidine variants completely lose their ability to transport both methylamine and ammonia. Molecular dynamics simulations indicated the molecular basis of the in vivo observations. They clearly showed that a single histidine variant (H168A or H318A) of AmtB confines the rather hydrophobic methylamine more strongly than ammonia around the mutated sites, resulting in dysfunction in conducting the former but not the latter molecule. PMF calculations further revealed that the single histidine variants form a potential energy well of up to 6 kcal/mol for methylamine, impairing conduction of this substrate. Unlike the single histidine variants, the double histidine variant, H168A/H318A, of AmtB was found to lose its unidirectional property of transporting both ammonia and methylamine. This could be attributed to a greatly increased frequency of opening of the entrance gate formed by F215 and F107, in this variant compared to wild-type, with a resultant lowering of the energy barrier for substrate to return to the periplasm.
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Affiliation(s)
- Jinan Wang
- Drug Discovery and Design Center, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
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14
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Hall JA, Yan D. The molecular basis of K+ exclusion by the Escherichia coli ammonium channel AmtB. J Biol Chem 2013; 288:14080-14086. [PMID: 23546877 DOI: 10.1074/jbc.m113.457952] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Members of the Amt family of channels mediate the transport of ammonium. The form of ammonium, NH3 or NH4(+), carried by these proteins remains controversial, and the mechanism by which they select against K(+) ions is unclear. We describe here a set of Escherichia coli AmtB proteins carrying mutations at the conserved twin-histidine site within the conduction pore that have altered substrate specificity and now transport K(+). Subsequent work established that AmtB-mediated K(+) uptake occurred against a concentration gradient and was membrane potential-dependent. These findings indicate that the twin-histidine element serves as a filter to prevent K(+) conduction and strongly support the notion that Amt proteins transport cations (NH4(+) or, in mutant proteins, K(+)) rather than NH3 gas molecules through their conduction pores.
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Affiliation(s)
- Jason A Hall
- Division of Biological Sciences, University of California San Diego, La Jolla, California 92093-0374.
| | - Dalai Yan
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana 46202-5120
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15
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Retracted article: ammonium transport proteins from Archaeoglobus fulgidus. J Physiol Biochem 2013; 69:963. [PMID: 23385667 DOI: 10.1007/s13105-012-0205-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2012] [Accepted: 07/26/2012] [Indexed: 10/28/2022]
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16
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Wang S, Orabi EA, Baday S, Bernèche S, Lamoureux G. Ammonium Transporters Achieve Charge Transfer by Fragmenting Their Substrate. J Am Chem Soc 2012; 134:10419-27. [DOI: 10.1021/ja300129x] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Shihao Wang
- Department of Chemistry and
Biochemistry and Centre for Research in Molecular Modeling (CERMM), Concordia University, 7141 Sherbrooke Street West,
Montréal, Québec H4B 1R6, Canada
| | - Esam A. Orabi
- Department of Chemistry and
Biochemistry and Centre for Research in Molecular Modeling (CERMM), Concordia University, 7141 Sherbrooke Street West,
Montréal, Québec H4B 1R6, Canada
| | - Sefer Baday
- Swiss Institute of Bioinformatics
and Biozentrum, University of Basel, Klingelbergstrasse
50/70, CH-4056 Basel, Switzerland
| | - Simon Bernèche
- Swiss Institute of Bioinformatics
and Biozentrum, University of Basel, Klingelbergstrasse
50/70, CH-4056 Basel, Switzerland
| | - Guillaume Lamoureux
- Department of Chemistry and
Biochemistry and Centre for Research in Molecular Modeling (CERMM), Concordia University, 7141 Sherbrooke Street West,
Montréal, Québec H4B 1R6, Canada
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17
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Ortiz-Ramirez C, Mora SI, Trejo J, Pantoja O. PvAMT1;1, a highly selective ammonium transporter that functions as H+/NH4(+) symporter. J Biol Chem 2011; 286:31113-22. [PMID: 21757699 PMCID: PMC3173114 DOI: 10.1074/jbc.m111.261693] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Revised: 07/04/2011] [Indexed: 01/26/2023] Open
Abstract
One of the main forms of nitrogen assimilated by microorganisms and plants is ammonium, despite its toxicity at low millimolar concentrations. Ammonium absorption has been demonstrated to be carried out by highly selective plasma membrane-located transporters of the AMT/MEP/Rh family and characterized by the presence of a well conserved hydrophobic pore through which ammonia is proposed to move. However, uncertainties exist regarding the exact chemical species transported by these membrane proteins, which can be in the form of either hydrophobic ammonia or charged ammonium. Here, we present the characterization of PvAMT1;1 from the common bean and demonstrate that it mediates the high affinity (micromolar), rapidly saturating (1 mM) electrogenic transport of ammonium. Activity of the transporter is enhanced by low extracellular pH, and associated with this acidic pH stimulation are changes in the reversal potential and cytoplasm acidification, indicating that PvAMT1;1 functions as an H(+)/NH(4)(+) symporter. Mutation analysis of a unique histidine present in PvAMT1;1 (H125R) leads to the stimulation of ammonium transport by decreasing the K(m) value by half and by increasing the V(max) 3-fold, without affecting the pH dependence of the symporter. In contrast, mutation of the first conserved histidine within the channel modifies the properties of PvAMT1;1, increasing its K(m) and V(max) values and transforming it into a pH-independent mechanism.
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Affiliation(s)
- Carlos Ortiz-Ramirez
- From the Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, A. P. 510-3, Colonia Miraval, Cuernavaca, Morelos 62250, México
| | - Silvia I. Mora
- From the Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, A. P. 510-3, Colonia Miraval, Cuernavaca, Morelos 62250, México
| | - Jorge Trejo
- From the Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, A. P. 510-3, Colonia Miraval, Cuernavaca, Morelos 62250, México
| | - Omar Pantoja
- From the Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, A. P. 510-3, Colonia Miraval, Cuernavaca, Morelos 62250, México
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18
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Uchikawa T, Yamamoto A, Inouye K. Origin and function of the stalk-cell vacuole in Dictyostelium. Dev Biol 2011; 352:48-57. [DOI: 10.1016/j.ydbio.2011.01.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Revised: 01/11/2011] [Accepted: 01/12/2011] [Indexed: 01/20/2023]
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19
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Periplasmic vestibule plays an important role for solute recruitment, selectivity, and gating in the Rh/Amt/MEP superfamily. Proc Natl Acad Sci U S A 2011; 108:3970-5. [PMID: 21368153 DOI: 10.1073/pnas.1007240108] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
AmtB, a member of the Rh/Amt/MEP superfamily, is responsible for ammonia transport in Escherichia coli. The ammonia pathway in AmtB consists of a narrow hydrophobic lumen in between hydrophilic periplasmic and cytoplasmic vestibules. A series of molecular dynamics simulations (greater than 0.4 μs in total) were performed to determine the mechanism of solute recruitments and selectivity by the periplasmic vestibule. The results show that the periplasmic vestibule plays a crucial role in solute selectivity, and its solute preferences follow the order of NH4(+) > NH3 > CO2. Based on our results, NH4(+) recruitment is initiated by its interaction with either E70 or E225, highly conserved residues located at the entrance of the vestibule. Subsequently, the backbone carbonyl groups at the periplasmic vestibule direct NH4(+) to the conserved aromatic cage at the bottom of the vestibule (known as the Am1 site). The umbrella sampling simulations suggest that the conserved residue D160 is not directly involved in the ammonia conduction; rather its main function is to keep the structure of periplasmic vestibule intact. The MD simulations also revealed that two partially stacked phenyl rings of F107 and F215, separating the periplasmic vestibule from the hydrophobic lumen, flip open and closed simultaneously with a frequency of approximately 10(8) flipping events per second. These results show how the periplasmic vestibule selectively recruits NH4(+) to the Am1 site, and also that the synchronized flipping of two phenyl rings potentially facilitates the solute transition from the periplasmic vestibule to the hydrophobic lumen in the Rh/Amt/MEP superfamily.
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20
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Wang J, Yang H, Zuo Z, Yan X, Wang Y, Luo X, Jiang H, Chen K, Zhu W. Molecular Dynamics Simulations on the Mechanism of Transporting Methylamine and Ammonia by Ammonium Transporter AmtB. J Phys Chem B 2010; 114:15172-9. [DOI: 10.1021/jp104508k] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Jinan Wang
- Drug Discovery and Design Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai, 201203, China, School of Biomedical Sciences, Curtin University of Technology, Perth WA 6485, Australia, and School of Science, East China University of Science and Technology, Shanghai, 200237, China
| | - Huaiyu Yang
- Drug Discovery and Design Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai, 201203, China, School of Biomedical Sciences, Curtin University of Technology, Perth WA 6485, Australia, and School of Science, East China University of Science and Technology, Shanghai, 200237, China
| | - Zhili Zuo
- Drug Discovery and Design Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai, 201203, China, School of Biomedical Sciences, Curtin University of Technology, Perth WA 6485, Australia, and School of Science, East China University of Science and Technology, Shanghai, 200237, China
| | - Xiuhua Yan
- Drug Discovery and Design Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai, 201203, China, School of Biomedical Sciences, Curtin University of Technology, Perth WA 6485, Australia, and School of Science, East China University of Science and Technology, Shanghai, 200237, China
| | - Yong Wang
- Drug Discovery and Design Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai, 201203, China, School of Biomedical Sciences, Curtin University of Technology, Perth WA 6485, Australia, and School of Science, East China University of Science and Technology, Shanghai, 200237, China
| | - Xiaomin Luo
- Drug Discovery and Design Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai, 201203, China, School of Biomedical Sciences, Curtin University of Technology, Perth WA 6485, Australia, and School of Science, East China University of Science and Technology, Shanghai, 200237, China
| | - Hualiang Jiang
- Drug Discovery and Design Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai, 201203, China, School of Biomedical Sciences, Curtin University of Technology, Perth WA 6485, Australia, and School of Science, East China University of Science and Technology, Shanghai, 200237, China
| | - Kaixian Chen
- Drug Discovery and Design Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai, 201203, China, School of Biomedical Sciences, Curtin University of Technology, Perth WA 6485, Australia, and School of Science, East China University of Science and Technology, Shanghai, 200237, China
| | - Weiliang Zhu
- Drug Discovery and Design Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai, 201203, China, School of Biomedical Sciences, Curtin University of Technology, Perth WA 6485, Australia, and School of Science, East China University of Science and Technology, Shanghai, 200237, China
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21
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Lamoureux G, Javelle A, Baday S, Wang S, Bernèche S. Transport mechanisms in the ammonium transporter family. Transfus Clin Biol 2010; 17:168-75. [DOI: 10.1016/j.tracli.2010.06.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2010] [Accepted: 06/14/2010] [Indexed: 02/09/2023]
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22
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Nakhoul NL, Abdulnour-Nakhoul SM, Schmidt E, Doetjes R, Rabon E, Hamm LL. pH sensitivity of ammonium transport by Rhbg. Am J Physiol Cell Physiol 2010; 299:C1386-97. [PMID: 20810915 DOI: 10.1152/ajpcell.00211.2010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Rhbg is a membrane glycoprotein that is involved in NH(3)/NH(4)(+) transport. Several models have been proposed to describe Rhbg, including an electroneutral NH(4)(+)/H(+) exchanger, a uniporter, an NH(4)(+) channel, or even a gas channel. In this study, we characterized the pH sensitivity of Rhbg expressed in Xenopus oocytes. We used two-electrode voltage clamp and ion-selective microelectrodes to measure NH(4)(+)-induced [and methyl ammonium (MA(+))] currents and changes in intracellular pH (pH(i)), respectively. In oocytes expressing Rhbg, 5 mM NH(4)Cl (NH(3)/NH(4)(+)) at extracellular pH (pH(o)) of 7.5 induced an inward current, decreased pH(i), and depolarized the cell. Raising pH(o) to 8.2 significantly enhanced the NH(4)(+)-induced current and pH(i) changes, whereas decreasing bath pH to 6.5 inhibited these changes. Lowering pH(i) (decreased by butyrate) also inhibited the NH(4)(+)-induced current and pH(i) decrease. In oocytes expressing Rhbg, 5 mM methyl amine hydrochloride (MA/MA(+)), often used as an NH(4)Cl substitute, induced an inward current, a pH(i) increase (not a decrease), and depolarization of the cell. Exposing the oocyte to MA/MA(+) at alkaline bath pH (8.2) enhanced the MA(+)-induced current, whereas lowering bath pH to 6.5 inhibited the MA(+) current completely. Exposing the oocyte to MA/MA(+) at low pH(i) abolished the MA(+)-induced current and depolarization; however, pH(i) still increased. These data indicate that 1) transport of NH(4)(+) and MA/MA(+) by Rhbg is pH sensitive; 2) electrogenic NH(4)(+) and MA(+) transport are stimulated by alkaline pH(o) but inhibited by acidic pH(i) or pH(o); and 3) electroneutral transport of MA by Rhbg is likely but is less sensitive to pH changes.
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Affiliation(s)
- Nazih L Nakhoul
- Section of Nephrology, Department of Medicine, Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana 70112, USA.
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23
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Huang CH, Ye M. The Rh protein family: gene evolution, membrane biology, and disease association. Cell Mol Life Sci 2010; 67:1203-18. [PMID: 19953292 PMCID: PMC11115862 DOI: 10.1007/s00018-009-0217-x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Revised: 11/10/2009] [Accepted: 11/12/2009] [Indexed: 11/25/2022]
Abstract
The Rh (Rhesus) genes encode a family of conserved proteins that share a structural fold of 12 transmembrane helices with members of the major facilitator superfamily. Interest in this family has arisen from the discovery of Rh factor's involvement in hemolytic disease in the fetus and newborn, and of its homologs widely expressed in epithelial tissues. The Rh factor and Rh-associated glycoprotein (RhAG), with epithelial cousins RhBG and RhCG, form four subgroups conferring upon vertebrates a genealogical commonality. The past decade has heralded significant advances in understanding the phylogenetics, allelic diversity, crystal structure, and biological function of Rh proteins. This review describes recent progress on this family and the molecular insights gleaned from its gene evolution, membrane biology, and disease association. The focus is on its long evolutionary history and surprising structural conservation from prokaryotes to humans, pointing to the importance of its functional role, related to but distinct from ammonium transport proteins.
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Affiliation(s)
- Cheng-Han Huang
- Laboratory of Biochemistry and Molecular Genetics, Lindsley F. Kimball Research Institute, New York Blood Center, New York, NY 10065, USA.
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24
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Abstract
In reviewing the structures of membrane proteins determined up to the end of 2009, we present in words and pictures the most informative examples from each family. We group the structures together according to their function and architecture to provide an overview of the major principles and variations on the most common themes. The first structures, determined 20 years ago, were those of naturally abundant proteins with limited conformational variability, and each membrane protein structure determined was a major landmark. With the advent of complete genome sequences and efficient expression systems, there has been an explosion in the rate of membrane protein structure determination, with many classes represented. New structures are published every month and more than 150 unique membrane protein structures have been determined. This review analyses the reasons for this success, discusses the challenges that still lie ahead, and presents a concise summary of the key achievements with illustrated examples selected from each class.
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25
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Goossens D, Trinh-Trang-Tan MM, Debbia M, Ripoche P, Vilela-Lamego C, Louache F, Vainchenker W, Colin Y, Cartron JP. Generation and characterisation of Rhd and Rhag null mice. Br J Haematol 2009; 148:161-72. [PMID: 19807729 DOI: 10.1111/j.1365-2141.2009.07928.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Mouse Rhd* and Rhag* genes were targeted using insertional vectors; the resulting knockout mice, and double-knockout descendants, were analysed. Rhag glycoprotein deficiency entailed defective assembly of the erythroid Rh complex with complete loss of Rh and intercellular adhesion molecule 4 (ICAM-4), but not CD47, expression. Absence of the Rh protein induced a loss of ICAM-4, and only a moderate reduction of Rhag expression. Double knockout phenotype was similar to that of Rhag targeted mice. Rhd and Rhag deficient mice exhibited neither the equivalent of human Rh(null) haemolytic anaemia nor any clinical or cellular abnormalities. Rhd-/- and Rhag-/- erythrocytes showed decreased basal adhesion to an endothelial cell line resulting from defective ICAM-4 membrane expression. There was no difference in recovery from phenylhydrazine-induced haematopoietic stress for double knockout mice as compared to controls, suggesting that ICAM-4 might be dispensable during stress erythropoiesis. Ammonia and methylammonia transport in erythrocytes was severely impaired in Rhag-/- but only slightly in Rhd-/- animals that significantly expressed Rhag, supporting the view that RhAG and Rhag, but not Rh, may act as ammonium transporters in human and mouse erythrocytes. These knockout mice should prove useful for further dissecting the physiological roles of Rh and Rhag proteins in the red cell membrane.
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Affiliation(s)
- Dominique Goossens
- Institut National de la Transfusion Sanguine, 6 rue Alexandre Cabanel, Paris, France.
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26
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Channel-like NH3flux by ammonium transporter AtAMT2. FEBS Lett 2009; 583:2833-8. [DOI: 10.1016/j.febslet.2009.07.039] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2009] [Accepted: 07/01/2009] [Indexed: 12/16/2022]
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27
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Nedelcu AM, Blakney AJC, Logue KD. Functional replacement of a primary metabolic pathway via multiple independent eukaryote-to-eukaryote gene transfers and selective retention. J Evol Biol 2009; 22:1882-94. [PMID: 19619164 DOI: 10.1111/j.1420-9101.2009.01797.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Although lateral gene transfer (LGT) is now recognized as a major force in the evolution of prokaryotes, the contribution of LGT to the evolution and diversification of eukaryotes is less understood. Notably, transfers of complete pathways are believed to be less likely between eukaryotes, because the successful transfer of a pathway requires the physical clustering of functionally related genes. Here, we report that in one of the closest unicellular relatives of animals, the choanoflagellate, Monosiga, three genes whose products work together in the glutamate synthase cycle are of algal origin. The concerted retention of these three independently acquired genes is best explained as the consequence of a series of adaptive replacement events. More generally, this study argues that (i) eukaryote-to-eukaryote transfers of entire metabolic pathways are possible, (ii) adaptive functional replacements of primary pathways can occur, and (iii) functional replacements involving eukaryotic genes are likely to have also contributed to the evolution of eukaryotes. Lastly, these data underscore the potential contribution of algal genes to the evolution of nonphotosynthetic lineages.
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Affiliation(s)
- A M Nedelcu
- Biology Department, University of New Brunswick, Fredericton, NB, Canada.
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28
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Ammonium ion transport by the AMT/Rh homolog TaAMT1;1 is stimulated by acidic pH. Pflugers Arch 2009; 458:733-43. [DOI: 10.1007/s00424-009-0665-z] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2009] [Revised: 03/09/2009] [Accepted: 03/12/2009] [Indexed: 01/14/2023]
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29
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Paz-Yepes J, Merino-Puerto V, Herrero A, Flores E. The amt gene cluster of the heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120. J Bacteriol 2008; 190:6534-9. [PMID: 18689479 PMCID: PMC2566009 DOI: 10.1128/jb.00613-08] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2008] [Accepted: 07/30/2008] [Indexed: 11/20/2022] Open
Abstract
The genome of the heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120 bears a gene cluster including three amt genes that, based on homology of their protein products, we designate amt4, amt1, and amtB. Expression of the three genes took place upon ammonium withdrawal in combined nitrogen-free medium and was NtcA dependent. The genes were transcribed independently, but an amt4-amt1 dicistronic transcript was also produced, and expression was highest for the amt1 gene. A mutant with the whole amt region removed could grow under laboratory conditions using ammonium, nitrate, or dinitrogen as the nitrogen source.
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Affiliation(s)
- Javier Paz-Yepes
- Instituto de Bioquímica Vegetal y Fotosíntesis, Centro de Investigaciones Científicas Isla de la Cartuja, Américo Vespucio 49, E-41092 Seville, Spain.
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30
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Substrate binding, deprotonation, and selectivity at the periplasmic entrance of the Escherichia coli ammonia channel AmtB. Proc Natl Acad Sci U S A 2008; 105:5040-5. [PMID: 18362341 DOI: 10.1073/pnas.0711742105] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The conduction mechanism of Escherichia coli AmtB, the structurally and functionally best characterized representative of the ubiquitous Amt/Rh family, has remained controversial in several aspects. The predominant view has been that it facilitates the movement of ammonium in its uncharged form as indicated by the hydrophobic nature of a pore located in the center of each subunit of the homotrimer. Using site-directed mutagenesis and a combination of biochemical and crystallographic methods, we have investigated mechanistic questions concerning the putative periplasmic ammonium ion binding site S1 and the adjacent periplasmic "gate" formed by two highly conserved phenylalanine residues, F107 and F215. Our results challenge models that propose that NH(4)(+) deprotonation takes place at S1 before NH(3) conduction through the pore. The presence of S1 confers two critical features on AmtB, both essential for its function: ammonium scavenging efficiency at very low ammonium concentration and selectivity against water and physiologically important cations. We show that AmtB activity absolutely requires F215 but not F107 and that removal or obstruction of the phenylalanine gate produces an open but inactive channel. The phenyl ring of F215 must thus play a very specific role in promoting transfer and deprotonation of substrate from S1 to the central pore. We discuss these results with respect to three distinct mechanisms of conduction that have been considered so far. We conclude that substrate deprotonation is an essential part of the conduction mechanism, but we do not rule out net electrogenic transport.
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31
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Abstract
Amt/MEP/Rh proteins are a family of integral membrane proteins implicated in the transport of NH3, CH(2)NH2, and CO2. Whereas Amt/MEP proteins are agreed to transport ammonia (NH3/NH4+), the primary substrate for Rh proteins has been controversial. Initial studies suggested that Rh proteins also transport ammonia, but more recent evidence suggests that they transport CO2. Here we report the first structure of an Rh family member, the Rh protein from the chemolithoautotrophic ammonia-oxidizing bacterium Nitrosomonas europaea. This Rh protein exhibits a number of similarities to its Amt cousins, including a trimeric oligomeric state, a central pore with an unusual twin-His site in the middle, and a Phe residue that blocks the channel for small-molecule transport. However, there are some significant differences, the most notable being the presence of an additional cytoplasmic C-terminal alpha-helix, an increased number of internal proline residues along the transmembrane helices, and a specific set of residues that appear to link the C-terminal helix to Phe blockage. This latter linkage suggests a mechanism in which binding of a partner protein to the C terminus could regulate channel opening. Another difference is the absence of the extracellular pi-cation binding site conserved in Amt/Mep structures. Instead, CO2 pressurization experiments identify a CO2 binding site near the intracellular exit of the channel whose residues are highly conserved in all Rh proteins, except those belonging to the Rh30 subfamily. The implications of these findings on the functional role of the human Rh antigens are discussed.
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32
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Fong RN, Kim KS, Yoshihara C, Inwood WB, Kustu S. The W148L substitution in the Escherichia coli ammonium channel AmtB increases flux and indicates that the substrate is an ion. Proc Natl Acad Sci U S A 2007; 104:18706-11. [PMID: 17998534 PMCID: PMC2141841 DOI: 10.1073/pnas.0709267104] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2007] [Indexed: 11/18/2022] Open
Abstract
The Amt/Mep ammonium channels are trimers in which each monomer contains a long, narrow, hydrophobic pore. Whether the substrate conducted by these pores is NH(3) or NH(4)(+) remains controversial. Substitution of leucine for the highly conserved tryptophan 148 residue at the external opening to Escherichia coli AmtB pores allowed us to address this issue. A strain carrying AmtB(W148L) accumulates much larger amounts of both [(14)C]methylammonium and [(14)C]methylglutamine in a washed cell assay than a strain carrying wild-type AmtB. Accumulation of methylammonium occurs within seconds and appears to reflect channel conductance, whereas accumulation of methylglutamine, which depends on the ATP-dependent activity of glutamine synthetase, increases for many minutes. Concentration of methylammonium was most easily studied in strains that lack glutamine synthetase. It is eliminated by the protonophore carbonyl cyanide m-chlorophenyl hydrazone and is approximately 10-fold higher in the strain carrying AmtB(W148L) than wild-type AmtB. The results indicate that AmtB allows accumulation of CH(3)NH(3)(+) ion in response to the electrical potential across the membrane and that the rate of flux through AmtB(W148L) is approximately 10 times faster than through wild-type AmtB. We infer that both mutant and wild-type proteins also carry NH(4)(+). Contrary to our previous views, we assess that E. coli AmtB does not differ from plant Amt proteins in this regard; both carry ions. We address the role of W148 in decreasing the activity and increasing the selectivity of AmtB and the implications of our findings with respect to the function of Rh proteins, the only known homologues of Amt/Mep proteins.
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Affiliation(s)
- Rebecca N. Fong
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720-3102
| | - Kwang-Seo Kim
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720-3102
| | - Corinne Yoshihara
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720-3102
| | - William B. Inwood
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720-3102
| | - Sydney Kustu
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720-3102
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Paz-Yepes J, Herrero A, Flores E. The NtcA-regulated amtB gene is necessary for full methylammonium uptake activity in the cyanobacterium Synechococcus elongatus. J Bacteriol 2007; 189:7791-8. [PMID: 17704220 PMCID: PMC2168756 DOI: 10.1128/jb.00404-07] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Amt proteins constitute a ubiquitous family of transmembrane ammonia channels that permit the net uptake of ammonium by cells. In many organisms, there is more than one amt gene, and these genes are subjected to nitrogen control. The mature Amt protein is a homo- or heterooligomer of three Amt subunits. We previously characterized an amt1 gene in the unicellular cyanobacterium Synechococcus elongatus strain PCC 7942. In this work, we describe the presence in this organism of a second amt gene, amtB, which encodes a protein more similar to the bacterial AmtB proteins than to any other characterized cyanobacterial Amt protein. The expression of amtB took place in response to nitrogen step-down, required the NtcA transcription factor, and occurred parallel to the expression of amt1. However, the transcript levels of amtB measured after 2 h of nitrogen deprivation were about 100-fold lower than those of amt1. An S. elongatus amtB insertional mutant exhibited an activity for uptake of [14C]methylammonium that was about 55% of that observed in the wild type, but inactivation of amtB had no noticeable effect on the uptake of ammonium when it was supplied at a concentration of 100 microM or more. Because an S. elongatus amt1 mutant is essentially devoid of [14C]methylammonium uptake activity, the mature Amt transporter is functional in the absence of AmtB subunits but not in the absence of Amt1 subunits. However, the S. elongatus amtB mutant could not concentrate [14C]methylammonium within the cells to the same extent as the wild type. Therefore, AmtB is necessary for full methylammonium uptake activity in S. elongatus.
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Affiliation(s)
- Javier Paz-Yepes
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla, Spain
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Yuan L, Loqué D, Kojima S, Rauch S, Ishiyama K, Inoue E, Takahashi H, von Wirén N. The organization of high-affinity ammonium uptake in Arabidopsis roots depends on the spatial arrangement and biochemical properties of AMT1-type transporters. THE PLANT CELL 2007; 19:2636-52. [PMID: 17693533 PMCID: PMC2002620 DOI: 10.1105/tpc.107.052134] [Citation(s) in RCA: 225] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
The AMMONIUM TRANSPORTER (AMT) family comprises six isoforms in Arabidopsis thaliana. Here, we describe the complete functional organization of root-expressed AMTs for high-affinity ammonium uptake. High-affinity influx of (15)N-labeled ammonium in two transposon-tagged amt1;2 lines was reduced by 18 to 26% compared with wild-type plants. Enrichment of the AMT1;2 protein in the plasma membrane and localization of AMT1;2 promoter activity in the endodermis and root cortex indicated that AMT1;2 mediates the uptake of ammonium entering the root via the apoplasmic transport route. An amt1;1 amt1;2 amt1;3 amt2;1 quadruple mutant (qko) showed severe growth depression under ammonium supply and maintained only 5 to 10% of wild-type high-affinity ammonium uptake capacity. Transcriptional upregulation of AMT1;5 in nitrogen-deficient rhizodermal and root hair cells and the ability of AMT1;5 to transport ammonium in yeast suggested that AMT1;5 accounts for the remaining uptake capacity in qko. Triple and quadruple amt insertion lines revealed in vivo ammonium substrate affinities of 50, 234, 61, and 4.5 muM for AMT1;1, AMT1;2, AMT1;3, and AMT1;5, respectively, but no ammonium influx activity for AMT2;1. These data suggest that two principle means of achieving effective ammonium uptake in Arabidopsis roots are the spatial arrangement of AMT1-type ammonium transporters and the distribution of their transport capacities at different substrate affinities.
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Affiliation(s)
- Lixing Yuan
- Molecular Plant Nutrition, Institute of Plant Nutrition, University of Hohenheim, D-70593 Stuttgart, Germany
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35
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Javelle A, Lupo D, Li XD, Merrick M, Chami M, Ripoche P, Winkler FK. Structural and mechanistic aspects of Amt/Rh proteins. J Struct Biol 2007; 158:472-81. [PMID: 17368911 DOI: 10.1016/j.jsb.2007.01.004] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2006] [Revised: 01/08/2007] [Accepted: 01/13/2007] [Indexed: 12/14/2022]
Abstract
Amt/Rh proteins, which mediate movement of ammonium across cell membranes, are spread throughout the three kingdoms of life. Most functional studies on various members of the family have been performed using cellular assays in heterologous expression systems, which are, however, not very well suited for detailed mechanistic studies. Although now generally considered to be ammonia conducting channels, based on a number of experimental studies and structural insights, the possibility remains that some plant Amts facilitate net ammonium ion transport. The Escherichia coli channel AmtB has become the model system of choice for analysis of the mechanism of ammonia conductance, increasingly also through molecular dynamics simulations. Further progress in a more detailed mechanistic understanding of these proteins requires a reliable in vitro assay using purified protein, allowing quantitative kinetic measurements under a variety of experimental conditions for different Amt/Rh proteins, including mutants. Here, we critically review the existing functional data in the context of the most interesting and unresolved mechanistic questions and we present our results, obtained using an in vitro assay set up with the purified E. coli channel AmtB.
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Affiliation(s)
- Arnaud Javelle
- Biomolecular Research, Paul Scherrer Institut, CH-5232 Villigen, Switzerland
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Neuhäuser B, Dynowski M, Mayer M, Ludewig U. Regulation of NH4+ transport by essential cross talk between AMT monomers through the carboxyl tails. PLANT PHYSIOLOGY 2007; 143:1651-9. [PMID: 17337531 PMCID: PMC1851830 DOI: 10.1104/pp.106.094243] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Ammonium transport across plant plasma membranes is facilitated by AMT/Rh-type ammonium transporters (AMTs), which also have homologs in most organisms. In the roots of the plant Arabidopsis (Arabidopsis thaliana), AMTs have been identified that function directly in the high-affinity NH4+ acquisition from soil. Here, we show that AtAMT1;2 has a distinct role, as it is located in the plasma membrane of the root endodermis. AtAMT1;2 functions as a comparatively low-affinity NH4+ transporter. Mutations at the highly conserved carboxyl terminus (C terminus) of AMTs, including one that mimics phosphorylation at a putative phosphorylation site, impair NH4+ transport activity. Coexpressing these mutants along with wild-type AtAMT1;2 substantially reduced the activity of the wild-type transporter. A molecular model of AtAMT1;2 provides a plausible explanation for the dominant inhibition, as the C terminus of one monomer directly contacts the neighboring subunit. It is suggested that part of the cytoplasmic C terminus of a single monomer can gate the AMT trimer. This regulatory mechanism for rapid and efficient inactivation of NH4+ transporters may apply to several AMT members to prevent excess influx of cytotoxic ammonium.
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Affiliation(s)
- Benjamin Neuhäuser
- Zentrum für Molekularbiologie der Pflanzen, Pflanzenphysiologie, Universität Tübingen, D-72076 Tuebingen, Germany
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Ludewig U, Neuhäuser B, Dynowski M. Molecular mechanisms of ammonium transport and accumulation in plants. FEBS Lett 2007; 581:2301-8. [PMID: 17397837 DOI: 10.1016/j.febslet.2007.03.034] [Citation(s) in RCA: 124] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2007] [Revised: 03/12/2007] [Accepted: 03/14/2007] [Indexed: 10/23/2022]
Abstract
The integral membrane proteins of the ammonium transporter (AMT/Rh) family provide the major route for shuttling ammonium (NH(4)(+)/NH(3)) across bacterial, archaeal, fungal and plant membranes. These proteins are distantly related to the Rh (rhesus) glycoproteins, which are absent in higher plants, but are present in many species, including bacteria and mammals. It appears that the large nitrogen requirement of plants resulted in unique strategies to acquire, capture and/or release ammonium. The biological function of plant ammonium transporters will be discussed and compared to other AMT/Rh proteins.
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Affiliation(s)
- Uwe Ludewig
- Zentrum für Molekularbiologie der Pflanzen (ZMBP), Pflanzenphysiologie, Universität Tübingen, Auf der Morgenstelle 1, 72076 Tübingen, Germany.
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Abstract
The brain ammonium production is detoxified by astrocytes, the gut ammonium production is detoxified by hepatic cells, and the renal ammonium production plays a major role in renal acid excretion. As a result of ammonium handling in these organs, the ammonium and pH values are strictly regulated in plasma. Up until recently, it was accepted that mammalian cell transmembrane ammonium transport was due to NH(4)(+) transport by non-specific transporting systems, and to non-ionic NH(3) diffusion, whereas lower organisms (such as bacteria, yeasts and plants) were endowed with specific ammonium transporters (Amts). Sequence homologies between Amts and human Rhesus (Rh) glycoproteins (RhAG, from erythroid cells, and RhBG and RhCG from epithelial cells) raised the hypothesis that Rh glycoproteins act as specific ammonium transporters, further sustained by the polarized distribution of RhBG and RhCG in gut, kidney and liver. Results from functional studies agree that Rh glycoproteins are the first ammonium transporters reported in mammals. However, the nature of the transported specie(s) is much debated: in particular, it is proposed that Rh glycoproteins mediate a direct NH(3) transport, or that they mediate an indirect NH(3) transport (resulting from NH(4)(+) for H(+) exchange). Direct NH(3) transport (associated or not with NH(4)(+) transport) raises the exciting hypothesis that Rh glycoproteins may also transport other gases than NH(3) (namely, CO(2)).
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Affiliation(s)
- Gabrielle Planelles
- Inserm, U806 et Université Paris Descartes, Faculté de Médecine René Descartes, Paris, France.
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