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Impact of Membrane Lipids on UapA and AzgA Transporter Subcellular Localization and Activity in Aspergillus nidulans. J Fungi (Basel) 2021; 7:jof7070514. [PMID: 34203131 PMCID: PMC8304608 DOI: 10.3390/jof7070514] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 06/24/2021] [Accepted: 06/24/2021] [Indexed: 12/21/2022] Open
Abstract
Recent biochemical and biophysical evidence have established that membrane lipids, namely phospholipids, sphingolipids and sterols, are critical for the function of eukaryotic plasma membrane transporters. Here, we study the effect of selected membrane lipid biosynthesis mutations and of the ergosterol-related antifungal itraconazole on the subcellular localization, stability and transport kinetics of two well-studied purine transporters, UapA and AzgA, in Aspergillus nidulans. We show that genetic reduction in biosynthesis of ergosterol, sphingolipids or phosphoinositides arrest A. nidulans growth after germling formation, but solely blocks in early steps of ergosterol (Erg11) or sphingolipid (BasA) synthesis have a negative effect on plasma membrane (PM) localization and stability of transporters before growth arrest. Surprisingly, the fraction of UapA or AzgA that reaches the PM in lipid biosynthesis mutants is shown to conserve normal apparent transport kinetics. We further show that turnover of UapA, which is the transporter mostly sensitive to membrane lipid content modification, occurs during its trafficking and by enhanced endocytosis, and is partly dependent on autophagy and Hect-type HulARsp5 ubiquitination. Our results point out that the role of specific membrane lipids on transporter biogenesis and function in vivo is complex, combinatorial and transporter-dependent.
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Kalampokis IF, Erban A, Amillis S, Diallinas G, Kopka J, Aliferis KA. Untargeted metabolomics as a hypothesis-generation tool in plant protection product discovery: Highlighting the potential of trehalose and glycerol metabolism of fungal conidiospores as novel targets. Metabolomics 2020; 16:79. [PMID: 32601735 DOI: 10.1007/s11306-020-01699-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Accepted: 06/15/2020] [Indexed: 12/11/2022]
Abstract
INTRODUCTION The production of high quality and safe food represents a main priority for the agri-food sector in the effort to sustain the exponentially growing human population. Nonetheless, there are major challenges that require the discovery of new, alternative, and improved plant protection products (PPPs). Focusing on fungal plant pathogens, the dissection of mechanisms that are essential for their survival provides insights that could be exploited towards the achievement of the aforementioned aim. In this context, the germination of fungal spores, which are essential structures for their dispersal, survival, and pathogenesis, represents a target of high potential for PPPs. To the best of our knowledge, no PPPs that target the germination of fungal spores currently exist. OBJECTIVES Within this context, we have mined for changes in the metabolite profiles of the model fungus Aspergillus nidulans FGSC A4 conidiospores during germination, in an effort to discover key metabolites and reactions that could potentially become targets of PPPs. METHODS Untargeted GC/EI-TOF/MS metabolomics and multivariate analyses were employed to monitor time-resolved changes in the metabolomes of germinating A. nidulans conidiospores. RESULTS Analyses revealed that trehalose hydrolysis plays a pivotal role in conidiospore germination and highlighted the osmoregulating role of the sugar alcohols, glycerol, and mannitol. CONCLUSION The ineffectiveness to introduce active ingredients that exhibit new mode(s)-of-action as fungicides, dictates the urge for the discovery of PPPs, which could be exploited to combat major plant protection issues. Based on the crucial role of trehalose hydrolysis in conidiospore dormancy breakage, and the subsequent involvement of glycerol in their germination, it is plausible to suggest their biosynthesis pathways as potential novel targets for the next-generation antifungal PPPs. Our study confirmed the applicability of untargeted metabolomics as a hypothesis-generation tool in PPPs' research and discovery.
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Affiliation(s)
- Ioannis F Kalampokis
- Laboratory of Pesticide Science, Agricultural University of Athens, Iera Odos 75, 118 55, Athens, Greece
| | - Alexander Erban
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Wissenschaftspark Golm, Am Mühlenberg 1, 14476, Potsdam, Germany
| | - Sotirios Amillis
- Department of Biology, National and Kapodistrian University of Athens, 15784, Panepistimioupolis, Athens, Greece
| | - George Diallinas
- Department of Biology, National and Kapodistrian University of Athens, 15784, Panepistimioupolis, Athens, Greece
| | - Joachim Kopka
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Wissenschaftspark Golm, Am Mühlenberg 1, 14476, Potsdam, Germany
| | - Konstantinos A Aliferis
- Laboratory of Pesticide Science, Agricultural University of Athens, Iera Odos 75, 118 55, Athens, Greece.
- Department of Plant Science, McGill University, 21111 Lakeshore Road, Montréal, H9X 3V9, Canada.
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Kalampokis IF, Kapetanakis GC, Aliferis KA, Diallinas G. Multiple nucleobase transporters contribute to boscalid sensitivity in Aspergillus nidulans. Fungal Genet Biol 2018; 115:52-63. [PMID: 29501616 DOI: 10.1016/j.fgb.2018.02.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2017] [Revised: 02/20/2018] [Accepted: 02/27/2018] [Indexed: 01/24/2023]
Abstract
The development of fungicide-resistant fungal populations represents a major challenge for the agrochemical and agri-food sectors, which threatens food supply and security. The issue becomes complex for fungi that cause quantitative and qualitative losses due to mycotoxin biosynthesis. Nonetheless, currently, the molecular details underlying fungicide action and fungal resistance mechanisms are partially known. Here, we have investigated whether plasma membrane transporters contribute to specific fungicide uptake in the model fungus Aspergillus nidulans. Independent physiological tests and toxicity screening of selected fungicides provided evidence that the antifungal activity of Succinate Dehydrogenase Inhibitors (SDHIs) is associated with the expression of several nucleobase-related transporters. In particular, it was shown that a strain genetically inactivated in all seven nucleobase-related transporters is resistant to the fungicide boscalid, whereas none of the single null mutants exhibited significant resistance level. By constructing and testing isogenic strains that over-express each one of the seven transporters, we confirmed that five of them, namely, UapC, AzgA, FycB, CntA, and FurA, contribute to boscalid uptake. Additionally, by employing metabolomics we have examined the effect of boscalid on the metabolism of isogenic strains expressing or genetically lacking boscalid-related nucleobase transporters. The results confirmed the involvement of specific nucleobase transporters in fungicide uptake, leading to the discovery of corresponding metabolites-biomarkers. This work is the first report on the involvement of specific transporters in fungicide uptake and toxicity and their impact on fungal metabolism regulation and results might be further exploited towards the deeper understanding of fungal resistance to fungicides.
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Affiliation(s)
- Ioannis F Kalampokis
- Laboratory of Pesticide Science, Agricultural University of Athens, Iera Odos 75, Athens 118 55, Greece
| | - George C Kapetanakis
- Department of Biology, National and Kapodistrian University of Athens, Panepistimioupolis, Athens 15784, Greece
| | - Konstantinos A Aliferis
- Laboratory of Pesticide Science, Agricultural University of Athens, Iera Odos 75, Athens 118 55, Greece.
| | - George Diallinas
- Department of Biology, National and Kapodistrian University of Athens, Panepistimioupolis, Athens 15784, Greece.
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Abstract
Cells need to communicate with their environment in order to obtain nutrients, grow, divide and respond to signals related to adaptation in changing physiological conditions or stress. A very basic question in biology is how cells, especially of those organisms living in rapidly changing habitats, sense their environment. Apparently, this question is of particular importance to all free-living microorganisms. The critical role of receptors, transporters and channels, transmembrane proteins located in the plasma membrane of all types of cells, in signaling environmental changes is well established. A relative newcomer in environment sensing are the so called transceptors, membrane proteins that possess both solute transport and receptor-like signaling activities. Now, the transceptor concept is further enlarged to include micronutrient sensing via the iron and zinc high-affinity transporters of Saccharomyces cerevisiae. Interestingly, what seems to underline the transport and/or sensing function of receptors, transporters and transceptors is ligand-induced conformational alterations recognized by downstream intracellular effectors.
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Affiliation(s)
- George Diallinas
- Department of Biology, National and Kapodistrian University of Athens, Panepistimioupolis 15784, Athens, Greece
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Barraco-Vega M, Romero H, Richero M, Cerdeiras MP, Cecchetto G. Functional characterization of two novel purine transporters from the Basidiomycota Phanerochaete chrysosporium. Gene 2017; 601:1-10. [PMID: 27923672 DOI: 10.1016/j.gene.2016.11.033] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 11/07/2016] [Accepted: 11/17/2016] [Indexed: 12/24/2022]
Abstract
Purine transporters as substrate entry points in organisms, are involved in a number of cellular processes such as nitrogen source uptake, energy metabolism and synthesis of nucleic acids. In this study, two nucleobase transporter genes (phZ, phU) from Phanerochaete chrysosporium were cloned, identified, and functionally characterized. Our results show that PhZ is a transporter of adenine and hypoxanthine, and a protein belonging to the AzgA-like family, whilst PhU belongs to the NAT/NCS2 family, transporting xanthine and uric acid. No other sequences belonging to these families were detected in P. chrysosporium's genome. Phylogenetic analyses show that AzgA-like sequences form monophyletic groups for each major lineage (Ascomycota, Basidiomycota and Zygomycota). In contrast, Ascomycota and Basidiomycota NAT/NCS2 sequences do not form monophyletic groups and several copies of this protein are distributed across the tree. Expression of phU was significantly downregulated in the presence of a primary source like ammonium, and enhanced if purines were present or if the mycelium was nitrogen starved. phZ was clearly induced by its substrates (hypoxanthine, adenine), very lightly induced by xanthine, suppressed by urea and amino acids and expressed at a basal level when uric acid or ammonium was the nitrogen source or when the mycelium was starved for nitrogen. In order to perform substrate analyses, both P. chrysosporium proteins (PhZ, PhU) were expressed in Aspergillus nidulans. Epifluorescent microscopy showed that under inducing conditions, PhZ-GFP and PhU-GFP were present at the plasma membrane of A. nidulans transformed strains, and were internalized in repressed conditions. Our results suggest that in the white-rot fungus P. chrysosporium, phU has a catabolic role and phZ, (less dependent of the nitrogen source), plays a key role in purine acquisition to provide biosynthetic components. These are the first purine transporters characterized in Basidiomycota.
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Affiliation(s)
- Mariana Barraco-Vega
- Microbiología Departamento de Biociencias, Facultad de Química, Universidad de la República, Montevideo 11800, Uruguay.
| | - Héctor Romero
- Laboratorio de Organización y Evolución del Genoma, Departamento de Ecología y Evolución, Facultad de Ciencias, Universidad de la República, Montevideo 11400, Uruguay
| | - Mariana Richero
- Microbiología Instituto de Química Biológica, Facultad de Ciencias - Facultad de Química, Universidad de la República, Montevideo 11800, Uruguay
| | - María Pía Cerdeiras
- Microbiología Departamento de Biociencias, Facultad de Química, Universidad de la República, Montevideo 11800, Uruguay
| | - Gianna Cecchetto
- Microbiología Instituto de Química Biológica, Facultad de Ciencias - Facultad de Química, Universidad de la República, Montevideo 11800, Uruguay
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Dissection of Transporter Function: From Genetics to Structure. Trends Genet 2016; 32:576-590. [DOI: 10.1016/j.tig.2016.06.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Revised: 06/20/2016] [Accepted: 06/21/2016] [Indexed: 12/20/2022]
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Wyatt TT, Wösten HAB, Dijksterhuis J. Fungal spores for dispersion in space and time. ADVANCES IN APPLIED MICROBIOLOGY 2016; 85:43-91. [PMID: 23942148 DOI: 10.1016/b978-0-12-407672-3.00002-2] [Citation(s) in RCA: 86] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Spores are an integral part of the life cycle of the gross majority of fungi. Their morphology and the mode of formation are both highly variable among the fungi, as is their resistance to stressors. The main aim for spores is to be dispersed, both in space, by various mechanisms or in time, by an extended period of dormancy. Some fungal ascospores belong to the most stress-resistant eukaryotic cells described to date. Stabilization is a process in which biomolecules and complexes thereof are protected by different types of molecules against heat, drought, or other molecules. This review discusses the most important compounds that are known to protect fungal spores and also addresses the biophysics of cell protection. It further covers the phenomena of dormancy, breaking of dormancy, and early germination. Germination is the transition from a dormant cell toward a vegetative cell and includes a number of specific changes. Finally, the applied aspects of spore biology are discussed.
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Affiliation(s)
- Timon T Wyatt
- Department of Applied and Industrial Mycology, CBS-KNAW Fungal Biodiversity Centre, Uppsalalaan 8, Utrecht, The Netherlands
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Evangelinos M, Martzoukou O, Chorozian K, Amillis S, Diallinas G. BsdA(Bsd2) -dependent vacuolar turnover of a misfolded version of the UapA transporter along the secretory pathway: prominent role of selective autophagy. Mol Microbiol 2016; 100:893-911. [PMID: 26917498 DOI: 10.1111/mmi.13358] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/19/2016] [Indexed: 12/13/2022]
Abstract
Transmembrane proteins translocate cotranslationally in the endoplasmic reticulum (ER) membrane and traffic as vesicular cargoes, via the Golgi, in their final membrane destination. Misfolding in the ER leads to protein degradation basically through the ERAD/proteasome system. Here, we use a mutant version of the purine transporter UapA (ΔR481) to show that specific misfolded versions of plasma membrane cargoes undergo vacuolar turnover prior to localization in the plasma membrane. We show that non-endocytic vacuolar turnover of ΔR481 is dependent on BsdA(Bsd2) , an ER transmembrane adaptor of HulA(Rsp5) ubiquitin ligase. We obtain in vivo evidence that BsdA(Bsd2) interacts with HulA(Rsp5) and ΔR481, primarily in the ER. Importantly, accumulation of ΔR481 in the ER triggers delivery of the selective autophagy marker Atg8 in vacuoles along with ΔR481. Genetic block of autophagy (atg9Δ, rabO(ts) ) reduces, but does not abolish, sorting of ΔR481 in the vacuoles, suggesting that a fraction of the misfolded transporter might be redirected for vacuolar degradation via the Golgi. Our results support that multiple routes along the secretory pathway operate for the detoxification of Aspergillus nidulans cells from misfolded membrane proteins and that BsdA is a key factor for marking specific misfolded cargoes.
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Affiliation(s)
- Minoas Evangelinos
- Faculty of Biology, University of Athens, Panepistimioupolis, 15784, Athens, Greece
| | - Olga Martzoukou
- Faculty of Biology, University of Athens, Panepistimioupolis, 15784, Athens, Greece
| | - Koar Chorozian
- Faculty of Biology, University of Athens, Panepistimioupolis, 15784, Athens, Greece
| | - Sotiris Amillis
- Faculty of Biology, University of Athens, Panepistimioupolis, 15784, Athens, Greece
| | - George Diallinas
- Faculty of Biology, University of Athens, Panepistimioupolis, 15784, Athens, Greece
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Characterization of AnNce102 and its role in eisosome stability and sphingolipid biosynthesis. Sci Rep 2015; 5:15200. [PMID: 26468899 PMCID: PMC4606592 DOI: 10.1038/srep15200] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 09/21/2015] [Indexed: 12/26/2022] Open
Abstract
The plasma membrane is implicated in a variety of functions, whose coordination necessitates highly dynamic organization of its constituents into domains of distinct protein and lipid composition. Eisosomes, at least partially, mediate this lateral plasma membrane compartmentalization. In this work, we show that the Nce102 homologue of Aspergillus nidulans colocalizes with eisosomes and plays a crucial role in density/number of PilA/SurG foci in the head of germlings. In addition we demonstrate that AnNce102 and PilA negatively regulate sphingolipid biosynthesis, since their deletions partially suppress the thermosensitivity of basA mutant encoding sphingolipid C4-hydroxylase and the growth defects observed upon treatment with inhibitors of sphingolipid biosynthesis, myriocin and Aureobasidin A. Moreover, we show that YpkA repression mimics genetic or pharmacological depletion of sphingolipids, conditions that induce the production of Reactive Oxygen Species (ROS), and can be partially overcome by deletion of pilA and/or annce102 at high temperatures. Consistent with these findings, pilAΔ and annce102Δ also show differential sensitivity to various oxidative agents, while AnNce102 overexpression can bypass sphingolipid depletion regarding the PilA/SurG foci number and organization, also leading to the mislocalization of PilA to septa.
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10
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Šimkovič M, Olejníková P, Mat'at'a M, Žemla P, Vilimová V, Farkašová L, Varečka L. Nutrient transport into germinating Trichoderma atroviride conidia and development of its driving force. MICROBIOLOGY-SGM 2015; 161:1240-50. [PMID: 25777081 DOI: 10.1099/mic.0.000079] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The exit from dormancy and the start of growth should be preceded or at least accompanied by the uptake of nutrients. In this work we studied changes in the transport of several nutrients into Trichoderma atroviride conidia. Germination started with a short period of isodiametric growth (conidial swelling), followed by polarized growth (germ tube formation) after about 8 h at 26 °C. The onset of isodiametric growth required the presence of external both phosphate and nitrate. At the same time, an increased uptake of precursors of macromolecules and phospholipids ((14)C- or (3)H-labelled valine, uracil, N-acetylglucosamine and choline) occurred. A low uptake of these precursors was observed also in non-germinating conidia. Concomitantly, this uptake developed an increased sensitivity to the uncoupler 3,3',4',5-tetrachlorosalicylanilide. Expression and activity of H(+)-ATPase started after completing isodiametric growth, suggesting that the proton-motive force (PMF) generated by H(+)-ATPase may be an accelerator of nutrient uptake and metabolism. (14)C-valine uptake was also measured into a mutant with disrupted pma1 gene. This mutant did not form conidia. The mutant also exhibited uncoupler sensitivity of (14)C-valine uptake. These observations showed that a PMF must have been generated by a mechanism(s) other than the H(+)-ATPase activity in the WT before H(+)-ATPase expression and in mycelia with disrupted H(+)-ATPase.
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Affiliation(s)
- Martin Šimkovič
- Department of Biochemistry and Microbiology, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 81237-Bratislava, Slovakia
| | - Petra Olejníková
- Department of Biochemistry and Microbiology, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 81237-Bratislava, Slovakia
| | - Matej Mat'at'a
- Department of Biochemistry and Microbiology, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 81237-Bratislava, Slovakia
| | - Peter Žemla
- Department of Biochemistry and Microbiology, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 81237-Bratislava, Slovakia
| | - Viera Vilimová
- Department of Biochemistry and Microbiology, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 81237-Bratislava, Slovakia
| | - Lenka Farkašová
- Department of Biochemistry and Microbiology, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 81237-Bratislava, Slovakia
| | - L'udovít Varečka
- Department of Biochemistry and Microbiology, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 81237-Bratislava, Slovakia
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Sá-Pessoa J, Amillis S, Casal M, Diallinas G. Expression and specificity profile of the major acetate transporter AcpA in Aspergillus nidulans. Fungal Genet Biol 2015; 76:93-103. [PMID: 25708319 DOI: 10.1016/j.fgb.2015.02.010] [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] [Received: 03/07/2014] [Revised: 02/06/2015] [Accepted: 02/10/2015] [Indexed: 12/27/2022]
Abstract
AcpA has been previously characterized as a high-affinity transporter essential for the uptake and use of acetate as sole carbon source in Aspergillus nidulans. Here, we follow the expression profile of AcpA and define its substrate specificity. AcpA-mediated acetate transport is detected from the onset of conidiospore germination, peaks at the time of germ tube emergence, and drops to low basal levels in germlings and young mycelia, where a second acetate transporter is also becoming apparent. AcpA activity also responds to acetate presence in the growth medium, but is not subject to either carbon or nitrogen catabolite repression. Short-chain monocarboxylates (benzoate, formate, butyrate and propionate) inhibit AcpA-mediated acetate transport with apparent inhibition constants (Ki) of 16.89±2.12, 9.25±1.01, 12.06±3.29 and 1.44±0.13mM, respectively. AcpA is also shown not to be directly involved in ammonia export, as proposed for its Saccharomyces cerevisiae homologue Ady2p. In the second part of this work, we search for the unknown acetate transporter expressed in mycelia, and for other transporters that might contribute to acetate uptake. In silico analysis, genetic construction of relevant null mutants, and uptake assays, reveal that the closest AcpA homologue (AN1839), named AcpB, is the 'missing' secondary acetate transporter in mycelia. We also identify two major short-chain carboxylate (lactate, succinate, pyruvate and malate) transporters, named JenA (AN6095) and JenB (AN6703), which however are not involved in acetate uptake. This work establishes a framework for further exploiting acetate and carboxylate transport in filamentous ascomycetes.
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Affiliation(s)
- Joana Sá-Pessoa
- Centre of Molecular and Environmental Biology (CBMA), Department of Biology, University of Minho, Campus de Gualtar, Braga 4710-057, Portugal
| | - Sotiris Amillis
- Faculty of Biology, Department of Botany, University of Athens, Panepistimioupolis, Athens 15781, Greece
| | - Margarida Casal
- Centre of Molecular and Environmental Biology (CBMA), Department of Biology, University of Minho, Campus de Gualtar, Braga 4710-057, Portugal.
| | - George Diallinas
- Faculty of Biology, Department of Botany, University of Athens, Panepistimioupolis, Athens 15781, Greece.
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Diallinas G. Understanding transporter specificity and the discrete appearance of channel-like gating domains in transporters. Front Pharmacol 2014; 5:207. [PMID: 25309439 PMCID: PMC4162363 DOI: 10.3389/fphar.2014.00207] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Accepted: 08/22/2014] [Indexed: 12/12/2022] Open
Abstract
Transporters are ubiquitous proteins mediating the translocation of solutes across cell membranes, a biological process involved in nutrition, signaling, neurotransmission, cell communication and drug uptake or efflux. Similarly to enzymes, most transporters have a single substrate binding-site and thus their activity follows Michaelis-Menten kinetics. Substrate binding elicits a series of structural changes, which produce a transporter conformer open toward the side opposite to the one from where the substrate was originally bound. This mechanism, involving alternate outward- and inward-facing transporter conformers, has gained significant support from structural, genetic, biochemical and biophysical approaches. Most transporters are specific for a given substrate or a group of substrates with similar chemical structure, but substrate specificity and/or affinity can vary dramatically, even among members of a transporter family that show high overall amino acid sequence and structural similarity. The current view is that transporter substrate affinity or specificity is determined by a small number of interactions a given solute can make within a specific binding site. However, genetic, biochemical and in silico modeling studies with the purine transporter UapA of the filamentous ascomycete Aspergillus nidulans have challenged this dogma. This review highlights results leading to a novel concept, stating that substrate specificity, but also transport kinetics and transporter turnover, are determined by subtle intramolecular interactions between a major substrate binding site and independent outward- or cytoplasmically-facing gating domains, analogous to those present in channels. This concept is supported by recent structural evidence from several, phylogenetically and functionally distinct transporter families. The significance of this concept is discussed in relationship to the role and potential exploitation of transporters in drug action.
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Krypotou E, Lambrinidis G, Evangelidis T, Mikros E, Diallinas G. Modelling, substrate docking and mutational analysis identify residues essential for function and specificity of the major fungal purine transporter AzgA. Mol Microbiol 2014; 93:129-45. [DOI: 10.1111/mmi.12646] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/08/2014] [Indexed: 01/07/2023]
Affiliation(s)
- Emilia Krypotou
- Faculty of Biology; University of Athens; Panepistimiopolis Athens 15784 Greece
| | - George Lambrinidis
- Faculty of Pharmacy; University of Athens; Panepistimiopolis Athens 15771 Greece
| | - Thomas Evangelidis
- Faculty of Pharmacy; University of Athens; Panepistimiopolis Athens 15771 Greece
| | - Emmanuel Mikros
- Faculty of Pharmacy; University of Athens; Panepistimiopolis Athens 15771 Greece
| | - George Diallinas
- Faculty of Biology; University of Athens; Panepistimiopolis Athens 15784 Greece
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Krypotou E, Diallinas G. Transport assays in filamentous fungi: Kinetic characterization of the UapC purine transporter of Aspergillus nidulans. Fungal Genet Biol 2014; 63:1-8. [DOI: 10.1016/j.fgb.2013.12.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Revised: 12/09/2013] [Accepted: 12/10/2013] [Indexed: 10/25/2022]
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dos Reis TF, Menino JF, Bom VLP, Brown NA, Colabardini AC, Savoldi M, Goldman MHS, Rodrigues F, Goldman GH. Identification of glucose transporters in Aspergillus nidulans. PLoS One 2013; 8:e81412. [PMID: 24282591 PMCID: PMC3839997 DOI: 10.1371/journal.pone.0081412] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Accepted: 10/12/2013] [Indexed: 11/18/2022] Open
Abstract
To characterize the mechanisms involved in glucose transport, in the filamentous fungus Aspergillus nidulans, we have identified four glucose transporter encoding genes hxtB-E. We evaluated the ability of hxtB-E to functionally complement the Saccharomyces cerevisiae EBY.VW4000 strain that is unable to grow on glucose, fructose, mannose or galactose as single carbon source. In S. cerevisiae HxtB-E were targeted to the plasma membrane. The expression of HxtB, HxtC and HxtE was able to restore growth on glucose, fructose, mannose or galactose, indicating that these transporters accept multiple sugars as a substrate through an energy dependent process. A tenfold excess of unlabeled maltose, galactose, fructose, and mannose were able to inhibit glucose uptake to different levels (50 to 80 %) in these s. cerevisiae complemented strains. Moreover, experiments with cyanide-m-chlorophenylhydrazone (CCCP), strongly suggest that hxtB, -C, and -E mediate glucose transport via active proton symport. The A. nidulans ΔhxtB, ΔhxtC or ΔhxtE null mutants showed ~2.5-fold reduction in the affinity for glucose, while ΔhxtB and -C also showed a 2-fold reduction in the capacity for glucose uptake. The ΔhxtD mutant had a 7.8-fold reduction in affinity, but a 3-fold increase in the capacity for glucose uptake. However, only the ΔhxtB mutant strain showed a detectable decreased rate of glucose consumption at low concentrations and an increased resistance to 2-deoxyglucose.
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Affiliation(s)
- Thaila Fernanda dos Reis
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, São Paulo, Brazil
| | - João Filipe Menino
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal
| | - Vinícius Leite Pedro Bom
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, São Paulo, Brazil
| | - Neil Andrew Brown
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, São Paulo, Brazil
| | - Ana Cristina Colabardini
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, São Paulo, Brazil
| | - Marcela Savoldi
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, São Paulo, Brazil
| | - Maria Helena S. Goldman
- Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, São Paulo, Brazil
| | - Fernando Rodrigues
- Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal
| | - Gustavo Henrique Goldman
- Laboratório Nacional de Ciência e Tecnologia do Bioetanol – CTBE, Campinas, São Paulo, Brazil
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, São Paulo, Brazil
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16
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Krypotou E, Diallinas G. Transport Assays in Aspergillus nidulans. Bio Protoc 2013. [DOI: 10.21769/bioprotoc.971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
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17
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Krypotou E, Kosti V, Amillis S, Myrianthopoulos V, Mikros E, Diallinas G. Modeling, substrate docking, and mutational analysis identify residues essential for the function and specificity of a eukaryotic purine-cytosine NCS1 transporter. J Biol Chem 2012; 287:36792-803. [PMID: 22969088 DOI: 10.1074/jbc.m112.400382] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The recent elucidation of crystal structures of a bacterial member of the NCS1 family, the Mhp1 benzyl-hydantoin permease from Microbacterium liquefaciens, allowed us to construct and validate a three-dimensional model of the Aspergillus nidulans purine-cytosine/H(+) FcyB symporter. The model consists of 12 transmembrane α-helical, segments (TMSs) and cytoplasmic N- and C-tails. A distinct core of 10 TMSs is made of two intertwined inverted repeats (TMS1-5 and TMS6-10) that are followed by two additional TMSs. TMS1, TMS3, TMS6, and TMS8 form an open cavity that is predicted to host the substrate binding site. Based on primary sequence alignment, three-dimensional topology, and substrate docking, we identified five residues as potentially essential for substrate binding in FcyB; Ser-85 (TMS1), Trp-159, Asn-163 (TMS3), Trp-259 (TMS6), and Asn-354 (TMS8). To validate the role of these and other putatively critical residues, we performed a systematic functional analysis of relevant mutants. We show that the proposed substrate binding residues, plus Asn-350, Asn-351, and Pro-353 are irreplaceable for FcyB function. Among these residues, Ser-85, Asn-163, Asn-350, Asn-351, and Asn-354 are critical for determining the substrate binding affinity and/or the specificity of FcyB. Our results suggest that Ser-85, Asn-163, and Asn-354 directly interact with substrates, Trp-159 and Trp-259 stabilize binding through π-π stacking interactions, and Pro-353 affects the local architecture of substrate binding site, whereas Asn-350 and Asn-351 probably affect substrate binding indirectly. Our work is the first systematic approach to address structure-function-specificity relationships in a eukaryotic member of NCS1 family by combining genetic and computational approaches.
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Affiliation(s)
- Emilia Krypotou
- Faculty of Biology, University of Athens, Panepistimiopolis, Athens 15784, Greece
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18
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Fekete E, de Vries RP, Seiboth B, vanKuyk PA, Sándor E, Fekete E, Metz B, Kubicek CP, Karaffa L. D-Galactose uptake is nonfunctional in the conidiospores of Aspergillus niger. FEMS Microbiol Lett 2012; 329:198-203. [PMID: 22324294 DOI: 10.1111/j.1574-6968.2012.02524.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2011] [Revised: 02/02/2012] [Accepted: 02/03/2012] [Indexed: 11/28/2022] Open
Abstract
The majority of black Aspergilli (Aspergillus section Nigri), including Aspergillus niger, as well as many other Ascomycetes fail to germinate on d-galactose as a sole carbon source. Here, we provide evidence that the ability of A. niger to transport D-galactose is growth stage dependent, being absent in the conidiospores but present in the mycelia. Despite earlier claims, we could identify galactokinase activity in growing cells and all genes of the Leloir pathway (responsible for channelling D-galactose into the EMP pathway) are well induced on D-galactose (and also on lactose, D-xylose and L-arabinose) in the mycelial stage. Expression of all Leloir pathway genes was also detectable in conidiospores, although galE (encoding a galactokinase) and galD (encoding a galactose-1-phosphate uridylyl transferase) were expressed poorly. These results suggest that the D-galactose-negative phenotype of A. niger conidiospores may be due to the lack of inducer uptake.
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Affiliation(s)
- Erzsébet Fekete
- Department of Biochemical Engineering, Faculty of Science and Technology, University of Debrecen, Debrecen, Hungary
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19
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Amillis S, Kosti V, Pantazopoulou A, Mikros E, Diallinas G. Mutational Analysis and Modeling Reveal Functionally Critical Residues in Transmembrane Segments 1 and 3 of the UapA Transporter. J Mol Biol 2011; 411:567-80. [DOI: 10.1016/j.jmb.2011.06.024] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Revised: 06/09/2011] [Accepted: 06/14/2011] [Indexed: 11/30/2022]
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20
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Abreu C, Sanguinetti M, Amillis S, Ramon A. UreA, the major urea/H+ symporter in Aspergillus nidulans. Fungal Genet Biol 2010; 47:1023-33. [PMID: 20633690 DOI: 10.1016/j.fgb.2010.07.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2010] [Revised: 06/16/2010] [Accepted: 07/08/2010] [Indexed: 10/19/2022]
Abstract
We report here the characterization of UreA, a high-affinity urea/H+ symporter of Aspergillus nidulans. The deletion of the encoding gene abolishes urea transport at low substrate concentrations, suggesting that in these conditions UreA is the sole transport system specific for urea in A. nidulans. The ureA gene is not inducible by urea or its precursors, but responds to nitrogen metabolite repression, necessitating for its expression the AreA GATA factor. In contrast to what was observed for other transporters in A. nidulans, repression by ammonium is also operative during the isotropic growth phase. The activity of UreA is down-regulated post-translationally by ammonium-promoted endocytosis. A number of homologues of UreA have been identified in A. nidulans and other Aspergilli, which cluster in four groups, two of which contain the urea transporters characterized so far in fungi and plants. This phylogeny may have arisen by gene duplication events, giving place to putative transport proteins that could have acquired novel, still unidentified functions.
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Affiliation(s)
- Cecilia Abreu
- Sección Bioquímica, Departamento de Biología Celular y Molecular, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
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21
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Bitsikas V, Karachaliou M, Gournas C, Diallinas G. Hypertonic conditions trigger transient plasmolysis, growth arrest and blockage of transporter endocytosis in Aspergillus nidulans and Saccharomyces cerevisiae. Mol Membr Biol 2010; 28:54-68. [PMID: 20919858 DOI: 10.3109/09687688.2010.510484] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
By using Aspergillus nidulans strains expressing functional GFP-tagged transporters under hypertonic conditions, we noticed the rapid appearance of cortical, relatively static, fluorescent patches (0.5-2.3 μm). These patches do not correspond to transporter microdomains as they co-localize with other plasma membrane-associated molecules, such as the pleckstrin homology (PH) domain and the SsoA t-Snare, or the lipophilic markers FM4-64 and filipin. In addition, they do not show characteristics of lipid rafts, MCCs or other membrane microdomains. Deconvoluted microscopic images showed that fluorescent patches correspond to plasma membrane invaginations. Transporters remain fully active during this phenomenon of localized plasmolysis. Plasmolysis was however associated with reduced growth rate and a dramatic blockage in transporter and FM4-64 endocytosis. These phenomena are transient and rapidly reversible upon wash-out of hypertonic media. Based on the observation that block in endocytosis by hypertonic treatment altered dramatically the cellular localization of tropomyosin (GFP-TpmA), although it did not affect the cortical appearance of upstream (SlaB-GFP) or downstream (AbpA-mRFP) endocytic components, we conclude that hypertonicity modifies actin dynamics and thus acts indirectly on endocytosis. This was further supported by the effect of latrunculin B, an actin depolymerization agent, on endocytosis. We show that the phenomena observed in A. nidulans also occur in Saccharomyces cerevisiae, suggesting that they constitute basic homeostatic responses of ascomycetes to hypertonic shock. Finally, our work shows that hypertonic treatments can be used as physiological tools to study the endocytic down-regulation of transporters in A. nidulans, as non-conditional genetic blocks affecting endocytic internalization are lethal or severely debilitating.
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Affiliation(s)
- Vassilis Bitsikas
- Faculty of Biology, Department of Botany, University of Athens, Panepistimioupolis, Athens, Greece
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22
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Leung J, Karachaliou M, Alves C, Diallinas G, Byrne B. Expression and purification of a functional uric acid-xanthine transporter (UapA). Protein Expr Purif 2010; 72:139-46. [PMID: 20153431 DOI: 10.1016/j.pep.2010.02.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2010] [Accepted: 02/03/2010] [Indexed: 11/19/2022]
Abstract
The Nucleobase-Ascorbate Transporters (NATs) family includes carriers with fundamental functions in uptake of key cellular metabolites, such as uric acid or vitamin C. The best studied example of a NAT transporter is the uric acid-xanthine permease (UapA) from the model ascomycete Aspergillus nidulans. Detailed genetic and biochemical analyses have revealed much about the mechanism of action of this protein; however, the difficulties associated with handling eukaryotic membrane proteins have limited efforts to elucidate the precise structure-function relationships of UapA by structural analysis. In this manuscript, we describe the heterologous overexpression of functional UapA as a fusion with GFP in different strains of Saccharomyces cerevisiae. The UapA-GFP construct expressed to 2.3 mg/L in a pep4Delta deletion strain lacking a key vacuolar endopeptidase and 3.8 mg/L in an npi1-1 mutant strain with defective Rsp5 ubiquitin ligase activity. Epifluorescence microscopy revealed that the UapA-GFP was predominately localized to the plasma membrane in both strains, although a higher intensity of fluorescence was observed for the npi1-1 mutant strain plasma membrane. In agreement with these observations, the npi1-1 mutant strain demonstrated a approximately 5-fold increase in uptake of [(3)H]-xanthine compared to the pep4Delta deletion strain. Despite yielding the best results for functional expression, in-gel fluorescence of the UapA-GFP expressed in the npi1-1 mutant strain revealed that the protein was subject to significant proteolytic degradation. Large scale expression of the protein using the pep4Delta deletion strain followed by purification produced mg quantities of pure, monodispersed protein suitable for further structural and functional studies. In addition, this work has generated a yeast cell based system for performing reverse genetics and other targeted approaches, in order to further understand the mechanism of action of this important model protein.
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Affiliation(s)
- James Leung
- Division of Molecular Biology, Imperial College London, South Kensington, London SW7 2AZ, UK
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23
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Gournas C, Amillis S, Vlanti A, Diallinas G. Transport-dependent endocytosis and turnover of a uric acid-xanthine permease. Mol Microbiol 2010; 75:246-60. [DOI: 10.1111/j.1365-2958.2009.06997.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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24
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Goudela S, Karatza P, Koukaki M, Frillingos S, Diallinas G. Comparative substrate recognition by bacterial and fungal purine transporters of the NAT/NCS2 family. Mol Membr Biol 2009; 22:263-75. [PMID: 16096268 DOI: 10.1080/09687860500093016] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
We compared the interactions of purines and purine analogues with representative fungal and bacterial members of the widespread Nucleobase-Ascorbate Transporter (NAT) family. These are: UapA, a well-studied xanthine-uric acid transporter of A. nidulans, Xut1, a novel transporter from C. albicans, described for the first time in this work, and YgfO, a recently characterized xanthine transporter from E. coli. Using transport inhibition experiments with 64 different purines and purine-related analogues, we describe a kinetic approach to build models on how NAT proteins interact with their substrates. UapA, Xut1 and YgfO appear to bind several substrates via interactions with both the pyrimidine and imidazol rings. Fungal homologues interact with the pyrimidine ring of xanthine and xanthine analogues via H-bonds, principally with N1-H and =O6, and to a lower extent with =O2. The E. coli homologue interacts principally with N3-H and =O2, and less strongly with N1-H and =O6. The basic interaction with the imidazol ring appears to be via a H-bond with N9. Interestingly, while all three homologues recognize xanthines with similar high affinities, interaction with uric acid or/and oxypurinol is transporter-specific. UapA recognizes uric acid with high affinity, principally via three H-bonds with =O2, =O6 and =O8. Xut1 has a 13-fold reduced affinity for uric acid, based on a different set of interactions involving =O8, and probably H atoms from positions N1, N3, N7 or N9. YgfO does not recognize uric acid at all. Both Xut1 and UapA recognize oxypurinol, but use different interactions reflected in a nearly 26-fold difference in their affinities for this drug, while YgfO interacts with this analogue very inefficiently.
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Affiliation(s)
- Sophia Goudela
- Department of Botany, University of Athens, Panepistimioupolis, Athens 15781, Greece
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25
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Amillis S, Hamari Z, Roumelioti K, Scazzocchio C, Diallinas G. Regulation of expression and kinetic modeling of substrate interactions of a uracil transporter inAspergillus nidulans. Mol Membr Biol 2009; 24:206-14. [PMID: 17520477 DOI: 10.1080/09687860601070806] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Early genetic evidence suggested that A. nidulans possesses at least one uracil transporter. A gene, named furD, was recently identified by reverse genetics and in silico approaches and we confirm here that it encodes a high-affinity, high-capacity, uracil transporter. In this work, we study the regulation of expression of FurD and develop a kinetic model describing transporter-substrate interactions. The furD gene is not expressed in resting conidiospores, is transcriptionally activated and reaches a peak during the isotropic growth phase of conidiospore germination, and stays at a basic low level in mycelium. Transcriptional expression is correlated to uracil transport activity. Expression in a strain blocked in uracil biosynthesis (pyrG-) is moderately increased and extended to later stages of germination. The presence of excess uracil in the medium leads to down-regulation of furD expression and FurD activity. A detailed kinetic analysis using a number of pyrimidine and purine analogues showed that FurD is able to recognize with high-affinity uracil (Km 0.45 microM), thymine (Ki 3.3 microM) and several 5-substituted analogues of uracil, and with moderate affinity uric acid and xanthine (Ki 94-99 microM). Kinetic evidence supports a model in which the positions N1-H, =O2, N3-H, =O4, as well as planarity play a central role for the substrate binding. This model, which rationalizes the unique specificity of FurD for uracil, is compared to and found to be very similar to analogous models for protozoan uracil transporters.
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Affiliation(s)
- Sotiris Amillis
- Faculty of Biology, Department of Botany, University of Athens, Panepistimioupolis, Athens, Greece
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26
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Karatza P, Frillingos S. Cloning and functional characterization of two bacterial members of the NAT/NCS2 family inEscherichia coli. Mol Membr Biol 2009; 22:251-61. [PMID: 16096267 DOI: 10.1080/09687860500092927] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The coding potential of the genome of E. coli K-12 includes YgfO and YicE, two members of the evolutionarily conserved NAT/NCS2 transporter family that are highly homologous to each other (45% residue identity) and closely related to UapA of Aspergillus nidulans, a most extensively studied microbial member of this family. YgfO and yicE were cloned from the genome, over-expressed extrachromosomally and assayed for uptake of [(3)H]xanthine and other nucleobases, in E. coli K-12, under conditions of negligible activity of the corresponding endogenous systems. Alternative, essentially equivalent functional versions of YgfO and YicE were engineered by C-terminal tagging with an epitope from the E. coli lactose permease and a biotin-acceptor domain from Klebsiella pneumoniae. Both YgfO and YicE were shown to be present in the plasma membrane of E. coli and function as specific, high-affinity transporters for xanthine (K(m) 4.2-4.6 microM for YgfO, or 2.9-3.8 microM for YicE), in a proton motive force-dependent manner; they display no detectable transport of uracil, hypoxanthine, or uric acid at external concentrations of up to 0.1 mM. Both YgfO and YicE are inefficient in recognizing uric acid or xanthine analogues modified at position 8 of the purine ring (8-methylxanthine, 8-azaxanthine, oxypurinol, allopurinol), which distinguishes them from their fungal homologues UapA and Xut1.
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Affiliation(s)
- Panayiota Karatza
- Laboratory of Biological Chemistry, University of Ioannina Medical School, Ioannina 45110, Greece
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27
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Hamari Z, Amillis S, Drevet C, Apostolaki A, Vágvölgyi C, Diallinas G, Scazzocchio C. Convergent evolution and orphan genes in the Fur4p-like family and characterization of a general nucleoside transporter inAspergillus nidulans. Mol Microbiol 2009; 73:43-57. [DOI: 10.1111/j.1365-2958.2009.06738.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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28
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AgtA, the dicarboxylic amino acid transporter of Aspergillus nidulans, is concertedly down-regulated by exquisite sensitivity to nitrogen metabolite repression and ammonium-elicited endocytosis. EUKARYOTIC CELL 2009; 8:339-52. [PMID: 19168757 DOI: 10.1128/ec.00270-08] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
We identified agtA, a gene that encodes the specific dicarboxylic amino acid transporter of Aspergillus nidulans. The deletion of the gene resulted in loss of utilization of aspartate as a nitrogen source and of aspartate uptake, while not completely abolishing glutamate utilization. Kinetic constants showed that AgtA is a high-affinity dicarboxylic amino acid transporter and are in agreement with those determined for a cognate transporter activity identified previously. The gene is extremely sensitive to nitrogen metabolite repression, depends on AreA for its expression, and is seemingly independent from specific induction. We showed that the localization of AgtA in the plasma membrane necessitates the ShrA protein and that an active process elicited by ammonium results in internalization and targeting of AgtA to the vacuole, followed by degradation. Thus, nitrogen metabolite repression and ammonium-promoted vacuolar degradation act in concert to downregulate dicarboxylic amino acid transport activity.
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29
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Lemuh ND, Diallinas G, Frillingos S, Mermelekas G, Karagouni AD, Hatzinikolaou DG. Purification and partial characterization of the xanthine-uric acid transporter (UapA) of Aspergillus nidulans. Protein Expr Purif 2009; 63:33-9. [DOI: 10.1016/j.pep.2008.08.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2008] [Revised: 08/19/2008] [Accepted: 08/19/2008] [Indexed: 11/26/2022]
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30
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Berg GM, Shrager J, Glöckner G, Arrigo KR, Grossman AR. UNDERSTANDING NITROGEN LIMITATION IN AUREOCOCCUS ANOPHAGEFFERENS (PELAGOPHYCEAE) THROUGH cDNA AND qRT-PCR ANALYSIS(1). JOURNAL OF PHYCOLOGY 2008; 44:1235-1249. [PMID: 27041720 DOI: 10.1111/j.1529-8817.2008.00571.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Brown tides of the marine pelagophyte Aureococcus anophagefferens Hargraves et Sieburth have been investigated extensively for the past two decades. Its growth is fueled by a variety of nitrogen (N) compounds, with dissolved organic nitrogen (DON) being particularly important during blooms. Characterization of a cDNA library suggests that A. anophagefferens can assimilate eight different forms of N. Expression of genes related to the sensing, uptake, and assimilation of inorganic and organic N, as well as the catabolic process of autophagy, was assayed in cells grown on different N sources and in N-limited cells. Growth on nitrate elicited an increase in the relative expression of nitrate and ammonium transporters, a nutrient stress-induced transporter, and a sensory kinase. Growth on urea increased the relative expression of a urea and a formate/nitrite transporter, while growth on ammonium resulted in an increase in the relative expression of an ammonium transporter, a novel ATP-binding cassette (ABC) transporter and a putative high-affinity phosphate transporter. N limitation resulted in a 30- to 110-fold increase in the relative expression of nitrate, ammonium, urea, amino acid/polyamine, and formate/nitrite transporters. A. anophagefferens demonstrated the highest relative accumulation of a transcript encoding a novel purine transporter, which was highly expressed across all N sources. This finding suggests that purines are an important source of N for the growth of this organism and could possibly contribute to the initiation and maintenance of blooms in the natural environment.
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Affiliation(s)
- Gry Mine Berg
- Department of Geophysics, Stanford University, 397 Panama Mall, Stanford, California 94305, USADepartment of Plant Biology, The Carnegie Institution, 260 Panama Street, Stanford, California 94305, USAGenome Analysis Group Leibniz Institute for Age Research - Fritz Lipmann Institute, Beutenbergstr. 11, D-07745 Jena, GermanyDepartment of Geophysics, Stanford University, 397 Panama Mall, Stanford, California 94305, USADepartment of Plant Biology, The Carnegie Institution, 260 Panama Street, Stanford, California 94305, USA
| | - Jeff Shrager
- Department of Geophysics, Stanford University, 397 Panama Mall, Stanford, California 94305, USADepartment of Plant Biology, The Carnegie Institution, 260 Panama Street, Stanford, California 94305, USAGenome Analysis Group Leibniz Institute for Age Research - Fritz Lipmann Institute, Beutenbergstr. 11, D-07745 Jena, GermanyDepartment of Geophysics, Stanford University, 397 Panama Mall, Stanford, California 94305, USADepartment of Plant Biology, The Carnegie Institution, 260 Panama Street, Stanford, California 94305, USA
| | - Gernot Glöckner
- Department of Geophysics, Stanford University, 397 Panama Mall, Stanford, California 94305, USADepartment of Plant Biology, The Carnegie Institution, 260 Panama Street, Stanford, California 94305, USAGenome Analysis Group Leibniz Institute for Age Research - Fritz Lipmann Institute, Beutenbergstr. 11, D-07745 Jena, GermanyDepartment of Geophysics, Stanford University, 397 Panama Mall, Stanford, California 94305, USADepartment of Plant Biology, The Carnegie Institution, 260 Panama Street, Stanford, California 94305, USA
| | - Kevin R Arrigo
- Department of Geophysics, Stanford University, 397 Panama Mall, Stanford, California 94305, USADepartment of Plant Biology, The Carnegie Institution, 260 Panama Street, Stanford, California 94305, USAGenome Analysis Group Leibniz Institute for Age Research - Fritz Lipmann Institute, Beutenbergstr. 11, D-07745 Jena, GermanyDepartment of Geophysics, Stanford University, 397 Panama Mall, Stanford, California 94305, USADepartment of Plant Biology, The Carnegie Institution, 260 Panama Street, Stanford, California 94305, USA
| | - Arthur R Grossman
- Department of Geophysics, Stanford University, 397 Panama Mall, Stanford, California 94305, USADepartment of Plant Biology, The Carnegie Institution, 260 Panama Street, Stanford, California 94305, USAGenome Analysis Group Leibniz Institute for Age Research - Fritz Lipmann Institute, Beutenbergstr. 11, D-07745 Jena, GermanyDepartment of Geophysics, Stanford University, 397 Panama Mall, Stanford, California 94305, USADepartment of Plant Biology, The Carnegie Institution, 260 Panama Street, Stanford, California 94305, USA
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Vlanti A, Diallinas G. The Aspergillus nidulans FcyB cytosine-purine scavenger is highly expressed during germination and in reproductive compartments and is downregulated by endocytosis. Mol Microbiol 2008; 68:959-77. [DOI: 10.1111/j.1365-2958.2008.06198.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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Goudela S, Reichard U, Amillis S, Diallinas G. Characterization and kinetics of the major purine transporters in Aspergillus fumigatus. Fungal Genet Biol 2008; 45:459-72. [PMID: 17881254 DOI: 10.1016/j.fgb.2007.08.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2007] [Revised: 07/30/2007] [Accepted: 08/01/2007] [Indexed: 11/30/2022]
Abstract
Three genes encoding putative purine transporters have been identified in silico in the genome of Aspergillus fumigatus by their very close similarity of their translation products to well-studied homologues in A. nidulans. Two of these transporters, called AfUapC and AfAzgA, were found responsible for bulk uptake of purines and studied in detail herein. Genetic knock-out analysis, regulation of transcription, direct purine uptake assays and heterologous expression in A. nidulans have unequivocally shown that AfUapC and AfAzgA are high-affinity, high-capacity, purine/H(+) symporters, the first being specific for xanthine, uric acid and oxypurinol, whereas the second for adenine, hypoxanthine, guanine and purine. The expression of these transporters is primarily controlled at the level of transcription. Transcription of both genes is purine-inducible, albeit with different efficiencies, whereas AfuapC is also ammonium-repressible. We characterised in detail the kinetics of the AfUapC and AfAzgA transporters, both in A. fumigatus and in A. nidulans, using a plethora of possible purine substrates. This analysis led us to propose kinetic models describing the molecular interactions of AfUapC and AfAzgA with purines. These models are discussed comparatively with analogous models from other purine transporters from fungi, bacteria and humans, and within the frame of a systematic development of novel purine-related antifungals.
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Affiliation(s)
- Sophia Goudela
- Faculty of Biology, Department of Botany, University of Athens, Panepistimioupolis, Athens 15781, Greece
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Gournas C, Papageorgiou I, Diallinas G. The nucleobase–ascorbate transporter (NAT) family: genomics, evolution, structure–function relationships and physiological role. MOLECULAR BIOSYSTEMS 2008; 4:404-16. [PMID: 18414738 DOI: 10.1039/b719777b] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Christos Gournas
- Faculty of Biology, Department of Botany, University of Athens, Panepistimioupolis, Athens, Greece
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Abstract
Early genetic and physiological work in bacteria and fungi has suggested the presence of highly specific nucleobase transport systems. Similar transport systems are now known to exist in algae, plants, protozoa and metazoa. Within the last 15 years, a small number of microbial genes encoding nucleobase transporters have been cloned and studied in great detail. The sequences of several other putative proteins submitted to databases are homologous to the microbial nucleobase transporters but their physiological functions remain largely undetermined. In this review, genetic, biochemical and molecular data are described concerning mostly the nucleobase transporters of Aspergillus nidulans and Saccharomyces cerevisiae, the two model ascomycetes from which the great majority of data come from. It is also discussed as to what is known on the nucleobase transporters of the two most significant pathogenic fungi: Candida albicans and Aspergillus fumigatus. Apart from highlighting how a basic process such as nucleobase recognition and transport operates, this review intends to highlight features that might be applicable to antifungal pharmacology.
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Affiliation(s)
- Areti Pantazopoulou
- Faculty of Biology, Department of Botany, University of Athens, Panepistimioupolis, Athens, Greece
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Schiedel AC, Meyer H, Alsdorf BBA, Gorzalka S, Brüssel H, Müller CE. [(3)H]Adenine is a suitable radioligand for the labeling of G protein-coupled adenine receptors but shows high affinity to bacterial contaminations in buffer solutions. Purinergic Signal 2007; 3:347-58. [PMID: 18404448 PMCID: PMC2072912 DOI: 10.1007/s11302-007-9060-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2007] [Accepted: 06/25/2007] [Indexed: 12/18/2022] Open
Abstract
[3H]Adenine has previously been used to label the newly discovered G protein-coupled murine adenine receptors. Recent reports have questioned the suitability of [3H]adenine for adenine receptor binding studies because of curious results, e.g. high specific binding even in the absence of mammalian protein. In this study, we showed that specific [3H]adenine binding to various mammalian membrane preparations increased linearly with protein concentration. Furthermore, we found that Tris-buffer solutions typically used for radioligand binding studies (50 mM, pH 7.4) that have not been freshly prepared but stored at 4°C for some time may contain bacterial contaminations that exhibit high affinity binding for [3H]adenine. Specific binding is abolished by heating the contaminated buffer or filtering it through 0.2-μm filters. Three different, aerobic, gram-negative bacteria were isolated from a contaminated buffer solution and identified as Achromobacter xylosoxidans, A. denitrificans, and Acinetobacter lwoffii. A. xylosoxidans, a common bacterium that can cause nosocomial infections, showed a particularly high affinity for [3H]adenine in the low nanomolar range. Structure–activity relationships revealed that hypoxanthine also bound with high affinity to A. xylosoxidans, whereas other nucleobases (uracil, xanthine) and nucleosides (adenosine, uridine) did not. The nature of the labeled site in bacteria is not known, but preliminary results indicate that it may be a high-affinity purine transporter. We conclude that [3H]adenine is a well-suitable radioligand for adenine receptor binding studies but that bacterial contamination of the employed buffer solutions must be avoided.
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Affiliation(s)
- Anke C Schiedel
- University of Bonn, Pharmaceutical Institute, Pharmaceutical Sciences Bonn (PSB), Pharmaceutical Chemistry I, Bonn, Germany
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Pantazopoulou A, Lemuh ND, Hatzinikolaou DG, Drevet C, Cecchetto G, Scazzocchio C, Diallinas G. Differential physiological and developmental expression of the UapA and AzgA purine transporters in Aspergillus nidulans. Fungal Genet Biol 2006; 44:627-40. [PMID: 17126042 DOI: 10.1016/j.fgb.2006.10.003] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2006] [Revised: 10/03/2006] [Accepted: 10/04/2006] [Indexed: 02/04/2023]
Abstract
In this article we study the cellular expression of UapA and AzgA, the two major purine transporters of Aspergillus nidulans, by constructing strains expressing, from their native promoters, fully functional fluorescent (UapA-sGFP, AzgA-sGFP) or immunological (UapA-His) chimeric transporters. Epifluorescence microscopy and immunodetection showed that under different physiological conditions and during Aspergillus development: (i) UapA and AzgA expression in the plasma membrane becomes evident early during germination and remains at a significant basal level in mycelium, (ii) Neither of the two transporters is expressed in the stalk, the vesicle, the phialides and the conidiospores, but surprisingly, UapA is specifically and strongly expressed in the periphery of metulae, (iii) Both transporters are expressed in ascogenous hyphae and in hülle cells but not in cleistothecia or ascospores, (iv) Purine induction leads to approximately 4-fold increase in UapA and AzgA protein content in mycelium, compatible with an analogous increase at the transcriptional level, (v) Ammonium leads to removal of UapA, but not of AzgA, from the plasma membrane by sorting of the protein to the vacuole.
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Affiliation(s)
- Areti Pantazopoulou
- Faculty of Biology, Department of Botany, University of Athens, Panepistimioupolis, Athens 15781, Greece
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Pantazopoulou A, Diallinas G. The first transmembrane segment (TMS1) of UapA contains determinants necessary for expression in the plasma membrane and purine transport. Mol Membr Biol 2006; 23:337-48. [PMID: 16923727 DOI: 10.1080/09687860600738239] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
UapA, a member of the NAT/NCS2 family, is a high affinity, high capacity, uric acid-xanthine/H+ symporter in Aspergillus nidulans. Determinants critical for substrate binding and transport lie in a highly conserved signature motif downstream from TMS8 and within TMS12. Here we examine the role of TMS1 in UapA biogenesis and function. First, using a mutational analysis, we studied the role of a short motif (Q85H86), conserved in all NATs. Q85 mutants were cryosensitive, decreasing (Q85L, Q85N, Q85E) or abolishing (Q85T) the capacity for purine transport, without affecting physiological substrate binding or expression in the plasma membrane. All H86 mutants showed nearly normal substrate binding affinities but most (H86A, H86K, H86D) were cryosensitive, a phenotype associated with partial ER retention and/or targeting of UapA in small vacuoles. Only mutant H86N showed nearly wild-type function, suggesting that His or Asn residues might act as H donors in interactions affecting UapA topology. Thus, residues Q85 and H86 seem to affect the flexibility of UapA, in a way that affects either transport catalysis per se (Q85), or expression in the plasma membrane (H86). We then examined the role of a transmembrane Leu Repeat (LR) motif present in TMS1 of UapA, but not in other NATs. Mutations replacing Leu with Ala residues altered differentially the binding affinities of xanthine and uric acid, in a temperature-sensitive manner. This result strongly suggested that the presence of L77, L84 and L91 affects the flexibility of UapA substrate binding site, in a way that is necessary for high affinity uric acid transport. A possible role of the LR motif in intramolecular interactions or in UapA dimerization is discussed.
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Affiliation(s)
- Areti Pantazopoulou
- Faculty of Biology, Department of Botany, University of Athens, Panepistimioupolis, Athens, Greece
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Erpapazoglou Z, Kafasla P, Sophianopoulou V. The product of the SHR3 orthologue of Aspergillus nidulans has restricted range of amino acid transporter targets. Fungal Genet Biol 2006; 43:222-33. [PMID: 16531082 DOI: 10.1016/j.fgb.2005.11.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2005] [Revised: 11/07/2005] [Accepted: 11/21/2005] [Indexed: 11/23/2022]
Abstract
The shrA gene of Aspergillus nidulans codes for a structural and functional homologue of Shr3p, a yeast ER membrane protein, which plays a crucial role in the secretory pathway of yeast amino acid permeases. shrA is a single-copy gene, whose expression is early activated during germination of A. nidulans conidiospores. ShrA is localized in the ER of the fungal cells and partially complements the shr3delta phenotype. Differently from Saccharomyces cerevisiae, where SHr3p is necessary for membrane localization of the majority of amino acid permeases, deletion of the shrA locus in A. nidulans impairs a limited number of amino acid uptake activities, including those responsible for proline and aspartate transport. Strongly reduced membrane levels of a PrnB-sGFP fusion in a shrAdelta background clearly suggest a direct role of ShrA in the topogenesis of the proline specific transporter.
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Affiliation(s)
- Z Erpapazoglou
- Institute of Biology, National Center for Scientific Research, Demokritos (NCSR D), Aghia Paraskevi, 153 10 Athens, Greece
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Vlanti A, Amillis S, Koukaki M, Diallinas G. A Novel-type Substrate-selectivity Filter and ER-exit Determinants in the UapA Purine Transporter. J Mol Biol 2006; 357:808-19. [PMID: 16464466 DOI: 10.1016/j.jmb.2005.12.070] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2005] [Revised: 12/07/2005] [Accepted: 12/20/2005] [Indexed: 11/26/2022]
Abstract
We present a functional analysis of the last alpha-helical transmembrane segment (TMS12) of UapA, a uric acid-xanthine/H+ symporter in Aspergillus nidulans and member of the nucleobase-ascorbate transporter (NAT) family. First, we performed a systematic mutational analysis of residue F528, located in the middle of TMS12, which was known to be critical for UapA specificity. Substitution of F528 with non-aromatic amino acid residues (Ala, Thr, Ser, Gln, Asn) did not affect significantly the kinetics of UapA for its physiological substrates, but allowed high-capacity transport of several novel purines and pyrimidines. Allele-specific combinations of F528 substitutions with mutations in Q408, a residue involved in purine binding, led to an array of UapA molecules with different kinetic and specificity profiles. We propose that F528 plays the role of a novel-type selectivity filter, which, in conjunction with a distinct purine-binding site, control UapA-mediated substrate translocation. We further studied the role of TMS12 by analysing the effect of its precise deletion and chimeric molecules in which TMS12 was substituted with analogous domains from other NATs. The presence of any of the TMS12 tested was necessary for ER-exit while their specific amino acid composition affected the kinetics of chimeras.
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Affiliation(s)
- Anna Vlanti
- Faculty of Biology, Department of Botany, University of Athens, Panepistimioupolis, Athens 15781, Greece
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40
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Koukaki M, Vlanti A, Goudela S, Pantazopoulou A, Gioule H, Tournaviti S, Diallinas G. The nucleobase-ascorbate transporter (NAT) signature motif in UapA defines the function of the purine translocation pathway. J Mol Biol 2005; 350:499-513. [PMID: 15953615 DOI: 10.1016/j.jmb.2005.04.076] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2005] [Revised: 04/19/2005] [Accepted: 04/29/2005] [Indexed: 11/21/2022]
Abstract
UapA, a member of the NAT/NCS2 family, is a high affinity, high capacity, uric acid-xanthine/H+ symporter of Aspergillus nidulans. We have previously presented evidence showing that a highly conserved signature motif ([Q/E/P]408-N-X-G-X-X-X-X-T-[R/K/G])417 is involved in UapA function. Here, we present a systematic mutational analysis of conserved residues in or close to the signature motif of UapA. We show that even the most conservative substitutions of residues Q408, N409 and G411 modify the kinetics and specificity of UapA, without affecting targeting in the plasma membrane. Q408 substitutions show that this residue determines both substrate binding and transport catalysis, possibly via interactions with position N9 of the imidazole ring of purines. Residue N409 is an irreplaceable residue necessary for transport catalysis, but is not involved in substrate binding. Residue G411 determines, indirectly, both the kinetics (K(m), V) and specificity of UapA, probably due to its particular property to confer local flexibility in the binding site of UapA. In silico predictions and a search in structural databases strongly suggest that the first part of the NAT signature motif of UapA (Q(408)NNG(411)) should form a loop, the structure of which is mostly affected by mutations in G411. Finally, substitutions of residues T416 and R417, despite being much better tolerated, can also affect the kinetics or the specificity of UapA. Our results show that the NAT signature motif defines the function of the UapA purine translocation pathway and strongly suggest that this might occur by determining the interactions of UapA with the imidazole part of purines.
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Affiliation(s)
- Marina Koukaki
- Faculty of Biology, Department of Botany, University of Athens, Panepistimioupolis, Athens 15781, Greece
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