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Kroef V, Ruegenberg S, Horn M, Allmeroth K, Ebert L, Bozkus S, Miethe S, Elling U, Schermer B, Baumann U, Denzel MS. GFPT2/GFAT2 and AMDHD2 act in tandem to control the hexosamine pathway. eLife 2022; 11:69223. [PMID: 35229715 PMCID: PMC8970586 DOI: 10.7554/elife.69223] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 02/28/2022] [Indexed: 11/25/2022] Open
Abstract
The hexosamine biosynthetic pathway (HBP) produces the essential metabolite UDP-GlcNAc and plays a key role in metabolism, health, and aging. The HBP is controlled by its rate-limiting enzyme glutamine fructose-6-phosphate amidotransferase (GFPT/GFAT) that is directly inhibited by UDP-GlcNAc in a feedback loop. HBP regulation by GFPT is well studied but other HBP regulators have remained obscure. Elevated UDP-GlcNAc levels counteract the glycosylation toxin tunicamycin (TM), and thus we screened for TM resistance in haploid mouse embryonic stem cells (mESCs) using random chemical mutagenesis to determine alternative HBP regulation. We identified the N-acetylglucosamine deacetylase AMDHD2 that catalyzes a reverse reaction in the HBP and its loss strongly elevated UDP-GlcNAc. To better understand AMDHD2, we solved the crystal structure and found that loss-of-function (LOF) is caused by protein destabilization or interference with its catalytic activity. Finally, we show that mESCs express AMDHD2 together with GFPT2 instead of the more common paralog GFPT1. Compared with GFPT1, GFPT2 had a much lower sensitivity to UDP-GlcNAc inhibition, explaining how AMDHD2 LOF resulted in HBP activation. This HBP configuration in which AMDHD2 serves to balance GFPT2 activity was also observed in other mESCs and, consistently, the GFPT2:GFPT1 ratio decreased with differentiation of human embryonic stem cells. Taken together, our data reveal a critical function of AMDHD2 in limiting UDP-GlcNAc production in cells that use GFPT2 for metabolite entry into the HBP.
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Affiliation(s)
- Virginia Kroef
- Molecular Genetics of Ageing, Max Planck Institute for Biology of Ageing, Cologne, Germany
| | - Sabine Ruegenberg
- Molecular Genetics of Ageing, Max Planck Institute for Biology of Ageing, Cologne, Germany
| | | | - Kira Allmeroth
- Molecular Genetics of Ageing, Max Planck Institute for Biology of Ageing, Cologne, Germany
| | | | | | - Stephan Miethe
- Molecular Genetics of Ageing, Max Planck Institute for Biology of Ageing, Cologne, Germany
| | - Ulrich Elling
- Vienna Biocenter, Austrian Academy of Sciences, Vienna, Austria
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2
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Ruegenberg S, Mayr FAMC, Atanassov I, Baumann U, Denzel MS. Protein kinase A controls the hexosamine pathway by tuning the feedback inhibition of GFAT-1. Nat Commun 2021; 12:2176. [PMID: 33846315 PMCID: PMC8041777 DOI: 10.1038/s41467-021-22320-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Accepted: 03/10/2021] [Indexed: 02/01/2023] Open
Abstract
The hexosamine pathway (HP) is a key anabolic pathway whose product uridine 5'-diphospho-N-acetyl-D-glucosamine (UDP-GlcNAc) is an essential precursor for glycosylation processes in mammals. It modulates the ER stress response and HP activation extends lifespan in Caenorhabditis elegans. The highly conserved glutamine fructose-6-phosphate amidotransferase 1 (GFAT-1) is the rate-limiting HP enzyme. GFAT-1 activity is modulated by UDP-GlcNAc feedback inhibition and via phosphorylation by protein kinase A (PKA). Molecular consequences of GFAT-1 phosphorylation, however, remain poorly understood. Here, we identify the GFAT-1 R203H substitution that elevates UDP-GlcNAc levels in C. elegans. In human GFAT-1, the R203H substitution interferes with UDP-GlcNAc inhibition and with PKA-mediated Ser205 phosphorylation. Our data indicate that phosphorylation affects the interactions of the two GFAT-1 domains to control catalytic activity. Notably, Ser205 phosphorylation has two discernible effects: it lowers baseline GFAT-1 activity and abolishes UDP-GlcNAc feedback inhibition. PKA controls the HP by uncoupling the metabolic feedback loop of GFAT-1.
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Affiliation(s)
- Sabine Ruegenberg
- grid.419502.b0000 0004 0373 6590Max Planck Institute for Biology of Ageing, Cologne, Germany ,grid.6190.e0000 0000 8580 3777Institute of Biochemistry, University of Cologne, Cologne, Germany
| | - Felix A. M. C. Mayr
- grid.419502.b0000 0004 0373 6590Max Planck Institute for Biology of Ageing, Cologne, Germany
| | - Ilian Atanassov
- grid.419502.b0000 0004 0373 6590Max Planck Institute for Biology of Ageing, Cologne, Germany
| | - Ulrich Baumann
- grid.6190.e0000 0000 8580 3777Institute of Biochemistry, University of Cologne, Cologne, Germany
| | - Martin S. Denzel
- grid.419502.b0000 0004 0373 6590Max Planck Institute for Biology of Ageing, Cologne, Germany ,grid.6190.e0000 0000 8580 3777CECAD - Cluster of Excellence, University of Cologne, Cologne, Germany ,grid.6190.e0000 0000 8580 3777Center for Molecular Medicine Cologne (CMMC), University of Cologne, Cologne, Germany
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3
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Plasmodium falciparum Apicomplexan-Specific Glucosamine-6-Phosphate N-Acetyltransferase Is Key for Amino Sugar Metabolism and Asexual Blood Stage Development. mBio 2020; 11:mBio.02045-20. [PMID: 33082260 PMCID: PMC7587441 DOI: 10.1128/mbio.02045-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Apicomplexan parasites cause a major burden on global health and economy. The absence of treatments, the emergence of resistances against available therapies, and the parasite’s ability to manipulate host cells and evade immune systems highlight the urgent need to characterize new drug targets to treat infections caused by these parasites. We demonstrate that glucosamine-6-phosphate N-acetyltransferase (GNA1), required for the biosynthesis of UDP-N-acetylglucosamine (UDP-GlcNAc), is essential for P. falciparum asexual blood stage development and that the disruption of the gene encoding this enzyme quickly causes the death of the parasite within a life cycle. The high-resolution crystal structure of the GNA1 ortholog from the apicomplexan parasite C. parvum, used here as a surrogate, highlights significant differences from human GNA1. These divergences can be exploited for the design of specific inhibitors against the malaria parasite. UDP-N-acetylglucosamine (UDP-GlcNAc), the main product of the hexosamine biosynthetic pathway, is an important metabolite in protozoan parasites since its sugar moiety is incorporated into glycosylphosphatidylinositol (GPI) glycolipids and N- and O-linked glycans. Apicomplexan parasites have a hexosamine pathway comparable to other eukaryotic organisms, with the exception of the glucosamine-phosphate N-acetyltransferase (GNA1) enzymatic step that has an independent evolutionary origin and significant differences from nonapicomplexan GNA1s. By using conditional genetic engineering, we demonstrate the requirement of GNA1 for the generation of a pool of UDP-GlcNAc and for the development of intraerythrocytic asexual Plasmodium falciparum parasites. Furthermore, we present the 1.95 Å resolution structure of the GNA1 ortholog from Cryptosporidium parvum, an apicomplexan parasite which is a leading cause of diarrhea in developing countries, as a surrogate for P. falciparum GNA1. The in-depth analysis of the crystal shows the presence of specific residues relevant for GNA1 enzymatic activity that are further investigated by the creation of site-specific mutants. The experiments reveal distinct features in apicomplexan GNA1 enzymes that could be exploitable for the generation of selective inhibitors against these parasites, by targeting the hexosamine pathway. This work underscores the potential of apicomplexan GNA1 as a drug target against malaria.
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Lockhart DEA, Stanley M, Raimi OG, Robinson DA, Boldovjakova D, Squair DR, Ferenbach AT, Fang W, van Aalten DMF. Targeting a critical step in fungal hexosamine biosynthesis. J Biol Chem 2020; 295:8678-8691. [PMID: 32341126 PMCID: PMC7324522 DOI: 10.1074/jbc.ra120.012985] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Revised: 04/22/2020] [Indexed: 01/06/2023] Open
Abstract
Aspergillus fumigatus is a human opportunistic fungal pathogen whose cell wall protects it from the extracellular environment including host defenses. Chitin, an essential component of the fungal cell wall, is synthesized from UDP-GlcNAc produced in the hexosamine biosynthetic pathway. As this pathway is critical for fungal cell wall integrity, the hexosamine biosynthesis enzymes represent potential targets of antifungal drugs. Here, we provide genetic and chemical evidence that glucosamine 6-phosphate N-acetyltransferase (Gna1), a key enzyme in this pathway, is an exploitable antifungal drug target. GNA1 deletion resulted in loss of fungal viability and disruption of the cell wall, phenotypes that could be rescued by exogenous GlcNAc, the product of the Gna1 enzyme. In a murine model of aspergillosis, the Δgna1 mutant strain exhibited attenuated virulence. Using a fragment-based approach, we discovered a small heterocyclic scaffold that binds proximal to the Gna1 active site and can be optimized to a selective submicromolar binder. Taken together, we have provided genetic, structural, and chemical evidence that Gna1 is an antifungal target in A. fumigatus.
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Affiliation(s)
- Deborah E A Lockhart
- School of Life Sciences, University of Dundee, Dundee, United Kingdom; Institute of Medical Sciences, Foresterhill, University of Aberdeen, Aberdeen, United Kingdom.
| | - Mathew Stanley
- School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Olawale G Raimi
- School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - David A Robinson
- Drug Discovery Unit, Wellcome Centre for Anti-Infectives Research, School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Dominika Boldovjakova
- Institute of Medical Sciences, Foresterhill, University of Aberdeen, Aberdeen, United Kingdom
| | - Daniel R Squair
- School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | | | - Wenxia Fang
- School of Life Sciences, University of Dundee, Dundee, United Kingdom
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5
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Raimi OG, Hurtado-Guerrero R, Borodkin V, Ferenbach A, Urbaniak MD, Ferguson MAJ, van Aalten DMF. A mechanism-inspired UDP- N-acetylglucosamine pyrophosphorylase inhibitor. RSC Chem Biol 2020; 1:13-25. [PMID: 34458745 PMCID: PMC8386105 DOI: 10.1039/c9cb00017h] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2019] [Accepted: 02/13/2020] [Indexed: 11/21/2022] Open
Abstract
UDP-N-acetylglucosamine pyrophosphorylase (UAP1) catalyses the last step in eukaryotic biosynthesis of uridine diphosphate-N-acetylglucosamine (UDP-GlcNAc), converting UTP and GlcNAc-1P to the sugar nucleotide. Gene disruption studies have shown that this gene is essential in eukaryotes and a possible antifungal target, yet no inhibitors of fungal UAP1 have so far been reported. Here we describe the crystal structures of substrate/product complexes of UAP1 from Aspergillus fumigatus that together provide snapshots of catalysis. A structure with UDP-GlcNAc, pyrophosphate and Mg2+ provides the first Michaelis complex trapped for this class of enzyme, revealing the structural basis of the previously reported Mg2+ dependence and direct observation of pyrophosphorolysis. We also show that a highly conserved lysine mimics the role of a second metal observed in structures of bacterial orthologues. A mechanism-inspired UTP α,β-methylenebisphosphonate analogue (meUTP) was designed and synthesized and was shown to be a micromolar inhibitor of the enzyme. The mechanistic insights and inhibitor described here will facilitate future studies towards the discovery of small molecule inhibitors of this currently unexploited potential antifungal drug target. UDP-N-acetylglucosamine pyrophosphorylase (UAP1) catalyses the last step in eukaryotic biosynthesis of uridine diphosphate-N-acetylglucosamine (UDP-GlcNAc), converting UTP and GlcNAc-1P to the sugar nucleotide.![]()
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Affiliation(s)
- Olawale G Raimi
- Division of Gene Regulation and Expression, School of Life Sciences, University of Dundee Dow Street DD1 5EH Dundee UK
| | - Ramon Hurtado-Guerrero
- Division of Gene Regulation and Expression, School of Life Sciences, University of Dundee Dow Street DD1 5EH Dundee UK
| | - Vladimir Borodkin
- Division of Gene Regulation and Expression, School of Life Sciences, University of Dundee Dow Street DD1 5EH Dundee UK
| | - Andrew Ferenbach
- Division of Gene Regulation and Expression, School of Life Sciences, University of Dundee Dow Street DD1 5EH Dundee UK
| | - Michael D Urbaniak
- Wellcome Centre for Anti-Infectives Research, School of Life Sciences, University of Dundee Dow Street DD1 5EH Dundee UK
| | - Michael A J Ferguson
- Wellcome Centre for Anti-Infectives Research, School of Life Sciences, University of Dundee Dow Street DD1 5EH Dundee UK
| | - Daan M F van Aalten
- Division of Gene Regulation and Expression, School of Life Sciences, University of Dundee Dow Street DD1 5EH Dundee UK
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6
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Aspergillus fumigatus Mitochondrial Acetyl Coenzyme A Acetyltransferase as an Antifungal Target. Appl Environ Microbiol 2020; 86:AEM.02986-19. [PMID: 32005728 PMCID: PMC7082573 DOI: 10.1128/aem.02986-19] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Accepted: 01/15/2020] [Indexed: 12/27/2022] Open
Abstract
Ergosterol plays an important role in maintaining cell membrane sterol homeostasis in fungi, and as such, it is considered an effective target in antifungal chemotherapy. In yeast, the enzyme acetyl-coenzyme A (CoA) acetyltransferase (ERG10) catalyzes the Claisen condensation of two acetyl-CoA molecules to acetoacetyl-CoA in the ergosterol biosynthesis pathway and is reported as being critical for cell viability. Using yeast ERG10 for alignment, two orthologues, AfERG10A (AFUB_000550) and AfERG10B (AFUB_083570), were discovered in the opportunistic fungal pathogen Aspergillus fumigatus Despite the essentiality of AfERG10B having been previously validated, the biological function of AfERG10A remains unclear. In this study, we have characterized recombinant AfERG10A as a functional acetyl-CoA acetyltransferase catalyzing both synthetic and degradative reactions. Unexpectedly, AfERG10A localizes to the mitochondria in A. fumigatus, as shown by C-terminal green fluorescent protein (GFP) tag fusion. Both knockout and inducible promoter strategies demonstrate that Aferg10A is essential for the survival of A. fumigatus The reduced expression of Aferg10A leads to severe morphological defects and increased susceptibility to oxidative and cell wall stresses. Although the catalytic mechanism of acetyl-CoA acetyltransferase family is highly conserved, the crystal structure of AfERG10A and its complex with CoA are solved, revealing four substitutions within the CoA binding site that are different from human orthologues. Taken together, our combination of genetic and structural studies demonstrates that mitochondrial AfERG10A is essential for A. fumigatus cell viability and could be a potential drug target to feed the antifungal drug development pipeline.IMPORTANCE A growing number of people worldwide are suffering from invasive aspergillosis caused by the human opportunistic fungal pathogen A. fumigatus Current therapeutic options rely on a limited repertoire of antifungals. Ergosterol is an essential component of the fungal cell membrane as well as a target of current antifungals. Approximately 20 enzymes are involved in ergosterol biosynthesis, of which acetyl-CoA acetyltransferase (ACAT) is the first enzyme. Two ACATs in A. fumigatus are AfErg10A and AfErg10B. However, the biological function of AfErg10A is yet to be investigated. In this study, we showed that AfErg10A is localized in the mitochondria and is essential for A. fumigatus survival and morphological development. In combination with structural studies, we validated AfErg10A as a potential drug target that will facilitate the development of novel antifungals and improve the efficiency of existing drugs.
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7
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Chen X, Zhang Z, Chen Z, Li Y, Su S, Sun S. Potential Antifungal Targets Based on Glucose Metabolism Pathways of Candida albicans. Front Microbiol 2020; 11:296. [PMID: 32256459 PMCID: PMC7093590 DOI: 10.3389/fmicb.2020.00296] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Accepted: 02/10/2020] [Indexed: 01/04/2023] Open
Abstract
In recent years, fungal infections have become a serious health problem. Candida albicans are considered as the fourth most common isolates associated with approximately 40% mortality in bloodstream infections among hospitalized patients. Due to various limitations of classical antifungals used currently, such as limited kinds of drugs, inevitable toxicities, and high price, there is an urgent need to explore new antifungal agents based on novel targets. Generally, nutrient metabolism is involved with fungal virulence, and glucose is one of the important nutrients in C. albicans. C. albicans can obtain and metabolize glucose through a variety of pathways; in theory, many enzymes in these pathways can be potential targets for developing new antifungal agents, and several studies have confirmed that compounds which interfere with alpha-glucosidase, acid trehalase, trehalose-6-phosphate synthase, class II fructose bisphosphate aldolases, and glucosamine-6-phosphate synthase in these pathways do have antifungal activities. In this review, the glucose metabolism pathways in C. albicans, the potential antifungal targets based on these pathways, and some compounds which have antifungal activities by inhibiting several enzymes in these pathways are summarized. We believe that our review will be helpful to the exploration of new antifungal drugs with novel antifungal targets.
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Affiliation(s)
- Xueqi Chen
- Department of Pharmacy, Shandong Provincial Qianfoshan Hospital, Shandong University, Jinan, China
- School of Pharmaceutical Sciences, Shandong University, Jinan, China
| | - Zewen Zhang
- Department of Imaging Medicine and Nuclear Medicine, Qilu Medical College, Shandong University, Jinan, China
| | - Zuozhong Chen
- Department of Pharmacy, Zibo Central Hospital, Zibo, China
| | - Yiman Li
- School of Pharmaceutical Sciences, Shandong University, Jinan, China
| | - Shan Su
- School of Pharmaceutical Sciences, Shandong University, Jinan, China
| | - Shujuan Sun
- Department of Clinical Pharmacy, The First Affiliated Hospital of Shandong First Medical University, Jinan, China
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8
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Ruegenberg S, Horn M, Pichlo C, Allmeroth K, Baumann U, Denzel MS. Loss of GFAT-1 feedback regulation activates the hexosamine pathway that modulates protein homeostasis. Nat Commun 2020; 11:687. [PMID: 32019926 PMCID: PMC7000685 DOI: 10.1038/s41467-020-14524-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Accepted: 01/14/2020] [Indexed: 01/03/2023] Open
Abstract
Glutamine fructose-6-phosphate amidotransferase (GFAT) is the key enzyme in the hexosamine pathway (HP) that produces uridine 5′-diphospho-N-acetyl-d-glucosamine (UDP-GlcNAc), linking energy metabolism with posttranslational protein glycosylation. In Caenorhabditis elegans, we previously identified gfat-1 gain-of-function mutations that elevate UDP-GlcNAc levels, improve protein homeostasis, and extend lifespan. GFAT is highly conserved, but the gain-of-function mechanism and its relevance in mammalian cells remained unclear. Here, we present the full-length crystal structure of human GFAT-1 in complex with various ligands and with important mutations. UDP-GlcNAc directly interacts with GFAT-1, inhibiting catalytic activity. The longevity-associated G451E variant shows drastically reduced sensitivity to UDP-GlcNAc inhibition in enzyme activity assays. Our structural and functional data point to a critical role of the interdomain linker in UDP-GlcNAc inhibition. In mammalian cells, the G451E variant potently activates the HP. Therefore, GFAT-1 gain-of-function through loss of feedback inhibition constitutes a potential target for the treatment of age-related proteinopathies. Mutations in the hexosamine pathway key enzyme glutamine fructose-6-phosphate amidotransferase (GFAT-1) improve protein quality control and extend C. elegans lifespan. Here the authors present the crystal structures of full-length human GFAT-1 alone and with bound ligands and perform activity assays, which show that gain-of-function in the longevity-associated G451E variant is caused by a loss of feedback regulation.
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Affiliation(s)
- Sabine Ruegenberg
- Max Planck Institute for Biology of Ageing, 50931, Cologne, Germany.,University of Cologne, Institute of Biochemistry, 50674, Cologne, Germany
| | - Moritz Horn
- Max Planck Institute for Biology of Ageing, 50931, Cologne, Germany
| | - Christian Pichlo
- University of Cologne, Institute of Biochemistry, 50674, Cologne, Germany
| | - Kira Allmeroth
- Max Planck Institute for Biology of Ageing, 50931, Cologne, Germany
| | - Ulrich Baumann
- University of Cologne, Institute of Biochemistry, 50674, Cologne, Germany.
| | - Martin S Denzel
- Max Planck Institute for Biology of Ageing, 50931, Cologne, Germany. .,CECAD-Cluster of Excellence, University of Cologne, 50931, Cologne, Germany. .,Center for Molecular Medicine Cologne (CMMC), University of Cologne, 50931, Cologne, Germany.
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9
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Martins MP, Silva LG, Rossi A, Sanches PR, Souza LDR, Martinez-Rossi NM. Global Analysis of Cell Wall Genes Revealed Putative Virulence Factors in the Dermatophyte Trichophyton rubrum. Front Microbiol 2019; 10:2168. [PMID: 31608026 PMCID: PMC6761320 DOI: 10.3389/fmicb.2019.02168] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Accepted: 09/04/2019] [Indexed: 12/25/2022] Open
Abstract
The fungal cell wall is a structure in constant contact with the external environment. It confers shape to the cell and protects it from external threats. During host adaptation, the cell wall structure of fungal pathogens is continuously reshaped by the orchestrated action of numerous genes. These genes respond to environmental stresses and challenging growth conditions, influencing the infective potential of the fungus. Here, we aimed to identify cell wall biosynthesis-related genes that putatively encode virulence factors in Trichophyton rubrum. We used RNA-seq to examine the impact of two drugs, namely undecanoic acid, and acriflavine as well as the effects of the carbon source switching from glucose to keratin on T. rubrum cell wall metabolism. By using functional annotation based on Gene Ontology terms, we identified significantly differentially expressed cell wall-related genes in all stress conditions. We also exposed T. rubrum to osmotic and other cell wall stressors and evaluated the susceptibility and gene modulation in response to stress. The changes in the ambient environment caused continuous cell wall remodeling, forcing the fungus to undergo modulatory restructuring. The influence of the external challenges indicated a highly complex response pattern. The genes that were modulated simultaneously in the three stress conditions highlight potential targets for antifungal development.
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Affiliation(s)
- Maíra P Martins
- Department of Genetics, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
| | - Larissa G Silva
- Department of Genetics, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
| | - Antonio Rossi
- Department of Genetics, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
| | - Pablo R Sanches
- Department of Genetics, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
| | - Larissa D R Souza
- Department of Genetics, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
| | - Nilce M Martinez-Rossi
- Department of Genetics, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil
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Cova M, López-Gutiérrez B, Artigas-Jerónimo S, González-Díaz A, Bandini G, Maere S, Carretero-Paulet L, Izquierdo L. The Apicomplexa-specific glucosamine-6-phosphate N-acetyltransferase gene family encodes a key enzyme for glycoconjugate synthesis with potential as therapeutic target. Sci Rep 2018; 8:4005. [PMID: 29507322 PMCID: PMC5838249 DOI: 10.1038/s41598-018-22441-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Accepted: 02/22/2018] [Indexed: 02/06/2023] Open
Abstract
Apicomplexa form a phylum of obligate parasitic protozoa of great clinical and veterinary importance. These parasites synthesize glycoconjugates for their survival and infectivity, but the enzymatic steps required to generate the glycosylation precursors are not completely characterized. In particular, glucosamine-phosphate N-acetyltransferase (GNA1) activity, needed to produce the essential UDP-N-acetylglucosamine (UDP-GlcNAc) donor, has not been identified in any Apicomplexa. We scanned the genomes of Plasmodium falciparum and representatives from six additional main lineages of the phylum for proteins containing the Gcn5-related N-acetyltransferase (GNAT) domain. One family of GNAT-domain containing proteins, composed by a P. falciparum sequence and its six apicomplexan orthologs, rescued the growth of a yeast temperature-sensitive GNA1 mutant. Heterologous expression and in vitro assays confirmed the GNA1 enzymatic activity in all lineages. Sequence, phylogenetic and synteny analyses suggest an independent origin of the Apicomplexa-specific GNA1 family, parallel to the evolution of a different GNA1 family in other eukaryotes. The inability to disrupt an otherwise modifiable gene target suggests that the enzyme is essential for P. falciparum growth. The relevance of UDP-GlcNAc for parasite viability, together with the independent evolution and unique sequence features of Apicomplexa GNA1, highlights the potential of this enzyme as a selective therapeutic target against apicomplexans.
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Affiliation(s)
- Marta Cova
- ISGlobal, Barcelona Ctr. Int. Health Res. (CRESIB), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain
| | - Borja López-Gutiérrez
- ISGlobal, Barcelona Ctr. Int. Health Res. (CRESIB), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain
| | - Sara Artigas-Jerónimo
- ISGlobal, Barcelona Ctr. Int. Health Res. (CRESIB), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain
| | - Aida González-Díaz
- ISGlobal, Barcelona Ctr. Int. Health Res. (CRESIB), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain
| | - Giulia Bandini
- Department of Molecular and Cell Biology, Boston University Goldman School of Dental Medicine, Boston, USA
| | - Steven Maere
- Ghent University, Department of Plant Biotechnology and Bioinformatics, B-9052, Ghent, Belgium
- VIB Center for Plant Systems Biology, B-9052, Ghent, Belgium
- Bioinformatics Institute Ghent, Ghent University, B-9052, Ghent, Belgium
| | - Lorenzo Carretero-Paulet
- Ghent University, Department of Plant Biotechnology and Bioinformatics, B-9052, Ghent, Belgium.
- VIB Center for Plant Systems Biology, B-9052, Ghent, Belgium.
- Bioinformatics Institute Ghent, Ghent University, B-9052, Ghent, Belgium.
| | - Luis Izquierdo
- ISGlobal, Barcelona Ctr. Int. Health Res. (CRESIB), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain.
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11
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Aboalroub AA, Bachman AB, Zhang Z, Keramisanou D, Merkler DJ, Gelis I. Acetyl group coordinated progression through the catalytic cycle of an arylalkylamine N-acetyltransferase. PLoS One 2017; 12:e0177270. [PMID: 28486510 PMCID: PMC5423648 DOI: 10.1371/journal.pone.0177270] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 04/25/2017] [Indexed: 11/18/2022] Open
Abstract
The transfer of an acetyl group from acetyl-CoA to an acceptor amine is a ubiquitous biochemical transformation catalyzed by Gcn5-related N-acetyltransferases (GNATs). Although it is established that the reaction proceeds through a sequential ordered mechanism, the role of the acetyl group in driving the ordered formation of binary and ternary complexes remains elusive. Herein, we show that CoA and acetyl-CoA alter the conformation of the substrate binding site of an arylalkylamine N-acetyltransferase (AANAT) to facilitate interaction with acceptor substrates. However, it is the presence of the acetyl group within the catalytic funnel that triggers high affinity binding. Acetyl group occupancy is relayed through a conserved salt bridge between the P-loop and the acceptor binding site, and is manifested as differential dynamics in the CoA and acetyl-CoA-bound states. The capacity of the acetyl group carried by an acceptor to promote its tight binding even in the absence of CoA, but also its mutually exclusive position to the acetyl group of acetyl-CoA underscore its importance in coordinating the progression of the catalytic cycle.
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Affiliation(s)
- Adam A. Aboalroub
- Department of Chemistry, University of South Florida, Tampa, Florida, United States of America
| | - Ashleigh B. Bachman
- Department of Chemistry, University of South Florida, Tampa, Florida, United States of America
| | - Ziming Zhang
- Department of Chemistry, University of South Florida, Tampa, Florida, United States of America
| | - Dimitra Keramisanou
- Department of Chemistry, University of South Florida, Tampa, Florida, United States of America
| | - David J. Merkler
- Department of Chemistry, University of South Florida, Tampa, Florida, United States of America
| | - Ioannis Gelis
- Department of Chemistry, University of South Florida, Tampa, Florida, United States of America
- * E-mail:
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12
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Salah Ud-Din AIM, Tikhomirova A, Roujeinikova A. Structure and Functional Diversity of GCN5-Related N-Acetyltransferases (GNAT). Int J Mol Sci 2016; 17:E1018. [PMID: 27367672 PMCID: PMC4964394 DOI: 10.3390/ijms17071018] [Citation(s) in RCA: 104] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Revised: 06/14/2016] [Accepted: 06/20/2016] [Indexed: 12/17/2022] Open
Abstract
General control non-repressible 5 (GCN5)-related N-acetyltransferases (GNAT) catalyze the transfer of an acyl moiety from acyl coenzyme A (acyl-CoA) to a diverse group of substrates and are widely distributed in all domains of life. This review of the currently available data acquired on GNAT enzymes by a combination of structural, mutagenesis and kinetic methods summarizes the key similarities and differences between several distinctly different families within the GNAT superfamily, with an emphasis on the mechanistic insights obtained from the analysis of the complexes with substrates or inhibitors. It discusses the structural basis for the common acetyltransferase mechanism, outlines the factors important for the substrate recognition, and describes the mechanism of action of inhibitors of these enzymes. It is anticipated that understanding of the structural basis behind the reaction and substrate specificity of the enzymes from this superfamily can be exploited in the development of novel therapeutics to treat human diseases and combat emerging multidrug-resistant microbial infections.
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Affiliation(s)
- Abu Iftiaf Md Salah Ud-Din
- Infection and Immunity Program, Monash Biomedicine Discovery Institute; Department of Microbiology, Monash University, Clayton, Victoria 3800, Australia.
| | - Alexandra Tikhomirova
- Infection and Immunity Program, Monash Biomedicine Discovery Institute; Department of Microbiology, Monash University, Clayton, Victoria 3800, Australia.
| | - Anna Roujeinikova
- Infection and Immunity Program, Monash Biomedicine Discovery Institute; Department of Microbiology, Monash University, Clayton, Victoria 3800, Australia.
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia.
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13
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Qin Z, Xiao Y, Yang X, Mesters JR, Yang S, Jiang Z. A unique GCN5-related glucosamine N-acetyltransferase region exist in the fungal multi-domain glycoside hydrolase family 3 β-N-acetylglucosaminidase. Sci Rep 2015; 5:18292. [PMID: 26669854 PMCID: PMC4680927 DOI: 10.1038/srep18292] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Accepted: 11/16/2015] [Indexed: 11/17/2022] Open
Abstract
Glycoside hydrolase (GH) family 3 β-N-acetylglucosaminidases widely exist in the filamentous fungi, which may play a key role in chitin metabolism of fungi. A multi-domain GH family 3 β-N-acetylglucosaminidase from Rhizomucor miehei (RmNag), exhibiting a potential N-acetyltransferase region, has been recently reported to show great potential in industrial applications. In this study, the crystal structure of RmNag was determined at 2.80 Å resolution. The three-dimensional structure of RmNag showed four distinctive domains, which belong to two distinguishable functional regions — a GH family 3 β-N-acetylglucosaminidase region (N-terminal) and a N-acetyltransferase region (C-terminal). From structural and functional analysis, the C-terminal region of RmNag was identified as a unique tandem array linking general control non-derepressible 5 (GCN5)-related N-acetyltransferase (GNAT), which displayed glucosamine N-acetyltransferase activity. Structural analysis of this glucosamine N-acetyltransferase region revealed that a unique glucosamine binding pocket is located in the pantetheine arm binding terminal region of the conserved CoA binding pocket, which is different from all known GNAT members. This is the first structural report of a glucosamine N-acetyltransferase, which provides novel structural information about substrate specificity of GNATs. The structural and functional features of this multi-domain β-N-acetylglucosaminidase could be useful in studying the catalytic mechanism of GH family 3 proteins.
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Affiliation(s)
- Zhen Qin
- College of Food Science and Nutritional Engineering, Beijing Advanced Innovation Center for Food Nutrition and Human Health, China Agricultural University, Beijing 100083, China
| | - Yibei Xiao
- Institute of Biochemistry, Center for Structural and Cell Biology in Medicine, University of Lübeck, Ratzeburger Allee 160, 23538, Lübeck, Germany
| | - Xinbin Yang
- College of Food Science and Nutritional Engineering, Beijing Advanced Innovation Center for Food Nutrition and Human Health, China Agricultural University, Beijing 100083, China
| | - Jeroen R Mesters
- Institute of Biochemistry, Center for Structural and Cell Biology in Medicine, University of Lübeck, Ratzeburger Allee 160, 23538, Lübeck, Germany
| | - Shaoqing Yang
- College of Food Science and Nutritional Engineering, Beijing Advanced Innovation Center for Food Nutrition and Human Health, China Agricultural University, Beijing 100083, China
| | - Zhengqiang Jiang
- College of Food Science and Nutritional Engineering, Beijing Advanced Innovation Center for Food Nutrition and Human Health, China Agricultural University, Beijing 100083, China
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14
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Brockhausen I, Nair DG, Chen M, Yang X, Allingham JS, Szarek WA, Anastassiades T. Human acetyl-CoA:glucosamine-6-phosphate N-acetyltransferase 1 has a relaxed donor specificity and transfers acyl groups up to four carbons in length. Biochem Cell Biol 2015; 94:197-204. [PMID: 26935656 DOI: 10.1139/bcb-2015-0115] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Glucosamine-6-phosphate N-acetyltransferase1 (GNA1) catalyses the transfer of an acetyl group from acetyl coenzyme A (AcCoA) to glucosamine-6-phosphate (GlcN6P) to form N-acetylglucosamine-6-phosphate (GlcNAc6P), which is an essential intermediate in UDP-GlcNAc biosynthesis. An analog of GlcNAc, N-butyrylglucosamine (GlcNBu) has shown healing properties for bone and articular cartilage in animal models of arthritis. The goal of this work was to examine whether GNA1 has the ability to transfer a butyryl group from butyryl-CoA to GlcN6P to form GlcNBu6P, which can then be converted to GlcNBu. We developed fluorescent and radioactive assays and examined the donor specificity of human GNA1. Acetyl, propionyl, n-butyryl, and isobutyryl groups were all transferred to GlcN6P, but isovaleryl-CoA and decanoyl-CoA did not serve as donor substrates. Site-specific mutants were produced to examine the role of amino acids potentially affecting the size and properties of the AcCoA binding pocket. All of the wild type and mutant enzymes showed activities of both acetyl and butyryl transfer and can therefore be used for the enzymatic synthesis of GlcNBu for biomedical applications.
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Affiliation(s)
- Inka Brockhausen
- a Department of Medicine, Division of Rheumatology, Queen's University, Kingston, ON K7L 3N6, Canada.,b Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Dileep G Nair
- a Department of Medicine, Division of Rheumatology, Queen's University, Kingston, ON K7L 3N6, Canada.,c Ministry of Higher Education, Sur College of Applied Sciences, Sur, Sultanate of Oman
| | - Min Chen
- b Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L 3N6, Canada.,d School of Life Sciences and The State Key Laboratory of Microbial Technology, Shandong University, Jinan, Shandong, 250100, China
| | - Xiaojing Yang
- b Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L 3N6, Canada
| | - John S Allingham
- b Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Walter A Szarek
- e Department of Chemistry, Queen's University, Kingston, ON K7L 3N6, Canada
| | - Tassos Anastassiades
- a Department of Medicine, Division of Rheumatology, Queen's University, Kingston, ON K7L 3N6, Canada.,b Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON K7L 3N6, Canada
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15
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Ma Y, Ghoshdastider U, Wang J, Ye W, Dötsch V, Filipek S, Bernhard F, Wang X. Cell-free expression of human glucosamine 6-phosphate N-acetyltransferase (HsGNA1) for inhibitor screening. Protein Expr Purif 2012; 86:120-6. [PMID: 23036358 DOI: 10.1016/j.pep.2012.09.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2012] [Revised: 09/20/2012] [Accepted: 09/23/2012] [Indexed: 12/27/2022]
Abstract
Glucosamine 6-phosphate N-acetyltransferase (GNA1; EC 2.3.1.4) is required for the de novo synthesis of N-acetyl-d-glucosamine-6-phosphate (GlcNAc-6P), which is an essential precursor in Uridine diphosphate N-acetylglucosamine (UDP-GlcNAc) biosynthesis pathway. Therefore, GNA1 is indispensable for the viability of organisms. Here, a novel cell-free expression strategy was developed to efficiently produce large amounts of human GNA1(HsGNA1) and HsGNA1-sGFP for throughput inhibitor screening. The binding site of inhibitor glucose-6-phosphate (G6P) to hGNA was identified by simulated annealing. Subtle differences to the binding site of Aspergillius GNA1(AfGNA1) can be harnessed for inhibitor design. HsGNA1 may be also useful as an antimicrobial and chemotherapeutic target against cancer. Additionally HsGNA1 inhibitors/modulators can possibly be administered with other drugs in the next generation of personalized medicine.
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Affiliation(s)
- Yi Ma
- School of Bioscience and Bioengineering, South China University of Technology, Guangzhou, China
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16
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Dorfmueller HC, Fang W, Rao FV, Blair DE, Attrill H, van Aalten DMF. Structural and biochemical characterization of a trapped coenzyme A adduct of Caenorhabditis elegans glucosamine-6-phosphate N-acetyltransferase 1. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2012; 68:1019-29. [PMID: 22868768 PMCID: PMC3413214 DOI: 10.1107/s0907444912019592] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Accepted: 05/02/2012] [Indexed: 01/31/2023]
Abstract
Glucosamine-6-phosphate N-acetyltransferase is an essential enzyme of the eukaryotic UDP-GlcNAc biosynthetic pathway. A crystal structure at 1.55 Å resolution revealed a highly unusual covalent product complex and biochemical studies investigated the function of a fully conserved active-site cysteine. Glucosamine-6-phosphate N-acetyltransferase 1 (GNA1) produces GlcNAc-6-phosphate from GlcN-6-phosphate and acetyl coenzyme A. Early mercury-labelling experiments implicated a conserved cysteine in the reaction mechanism, whereas recent structural data appear to support a mechanism in which this cysteine plays no role. Here, two crystal structures of Caenorhabditis elegans GNA1 are reported, revealing an unusual covalent complex between this cysteine and the coenzyme A product. Mass-spectrometric and reduction studies showed that this inactive covalent complex can be reactivated through reduction, yet mutagenesis of the cysteine supports a previously reported bi-bi mechanism. The data unify the apparently contradictory earlier reports on the role of a cysteine in the GNA1 active site.
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Affiliation(s)
- Helge C Dorfmueller
- Division of Molecular Microbiology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland
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Evolution of insect arylalkylamine N-acetyltransferases: structural evidence from the yellow fever mosquito, Aedes aegypti. Proc Natl Acad Sci U S A 2012; 109:11669-74. [PMID: 22753468 DOI: 10.1073/pnas.1206828109] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Arylalkylamine N-acetyltransferase (aaNAT) catalyzes the transacetylation from acetyl-CoA to arylalkylamines. aaNATs are involved in sclerotization and neurotransmitter inactivation in insects. Phyletic distribution analysis confirms three clusters of aaNAT-like sequences in insects: typical insect aaNAT, polyamine NAT-like aaNAT, and mosquito unique putative aaNAT (paaNAT). Here we studied three proteins: aaNAT2, aaNAT5b, and paaNAT7, each from a different cluster. aaNAT2, a protein from the typical insect aaNAT cluster, uses histamine as a substrate as well as the previously identified arylalkylamines. aaNAT5b, a protein from polyamine NAT -like aaNAT cluster, uses hydrazine and histamine as substrates. The crystal structure of aaNAT2 was determined using single-wavelength anomalous dispersion methods, and that of native aaNAT2, aaNAT5b and paaNAT7 was detected using molecular replacement techniques. All three aaNAT structures have a common fold core of GCN5-related N-acetyltransferase superfamily proteins, along with a unique structural feature: helix/helices between β3 and β4 strands. Our data provide a start toward a more comprehensive understanding of the structure-function relationship and physiology of aaNATs from the mosquito Aedes aegypti and serve as a reference for studying the aaNAT family of proteins from other insect species. The structures of three different types of aaNATs may provide targets for designing insecticides for use in mosquito control.
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18
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Characterization, localization, essentiality, and high-resolution crystal structure of glucosamine 6-phosphate N-acetyltransferase from Trypanosoma brucei. EUKARYOTIC CELL 2011; 10:985-97. [PMID: 21531872 DOI: 10.1128/ec.05025-11] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A gene predicted to encode Trypanosoma brucei glucosamine 6-phosphate N-acetyltransferase (TbGNA1; EC 2.3.1.4) was cloned and expressed in Escherichia coli. The recombinant protein was enzymatically active, and its high-resolution crystal structure was obtained at 1.86 Å. Endogenous TbGNA1 protein was localized to the peroxisome-like microbody, the glycosome. A bloodstream-form T. brucei GNA1 conditional null mutant was constructed and shown to be unable to sustain growth in vitro under nonpermissive conditions, demonstrating that there are no metabolic or nutritional routes to UDP-GlcNAc other than via GlcNAc-6-phosphate. Analysis of the protein glycosylation phenotype of the TbGNA1 mutant under nonpermissive conditions revealed that poly-N-acetyllactosamine structures were greatly reduced in the parasite and that the glycosylation profile of the principal parasite surface coat component, the variant surface glycoprotein (VSG), was modified. The significance of results and the potential of TbGNA1 as a novel drug target for African sleeping sickness are discussed.
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Hu X, Zhang W, Carmichael I, Serianni AS. Amide cis-trans isomerization in aqueous solutions of methyl N-formyl-D-glucosaminides and methyl N-acetyl-D-glucosaminides: chemical equilibria and exchange kinetics. J Am Chem Soc 2010; 132:4641-52. [PMID: 20225805 DOI: 10.1021/ja9086787] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Amide cis-trans isomerization (CTI) in methyl 2-deoxy-2-acylamido-d-glucopyranosides was investigated by (1)H and (13)C NMR spectroscopy. Singly (13)C-labeled methyl 2-deoxy-2-formamido-d-glucopyranoside (MeGlcNFm) anomers provided standard (1)H and (13)C chemical shifts and (1)H-(1)H and (13)C-(13)C spin-coupling constants for cis and trans amides that are detected readily in aqueous solution. Equipped with this information, doubly (13)C-labeled methyl 2-deoxy-2-acetamido-d-glucopyranoside (MeGlcNAc) anomers were investigated, leading to the detection and quantification of cis and trans amides in this biologically important aminosugar. In comparison to MeGlcNFm anomers, the percentage of cis amide in aqueous solutions of MeGlcNAc anomers is small ( approximately 23% for MeGlcNFm versus approximately 1.8% for MeGlcNAc at 42 degrees C) but nevertheless observable with assistance from (13)C-labeling. Temperature studies gave thermodynamic parameters DeltaG degrees , DeltaH degrees , and DeltaS degrees for cis-trans interconversion in MeGlcNFm and MeGlcNAc anomers. Cis/trans equilibria depended on anomeric configuration, with solutions of alpha-anomers containing less cis amide than those of beta-anomers. Confirmation of the presence of cis amide in MeGlcNAc solutions derived from quantitative (13)C saturation transfer measurements of CTI rate constants as a function of solution temperature, yielding activation parameters E(act), DeltaG degrees (), DeltaH degrees (), and DeltaS degrees () for saccharide CTI. Rate constants for the conversion of trans to cis amide in MeGlcNFm and MeGlcNAc anomers ranged from 0.02 to 3.59 s(-1) over 31-85 degrees C, compared to 0.24-80 s(-1) for the conversion of cis to trans amide over the same temperature range. Energies of activation ranged from 16-19 and 19-20 kcal/mol for the cis --> trans and trans --> cis processes, respectively. Complementary DFT calculations on MeGlcNFm and MeGlcNAc model structures were conducted to evaluate the effects of an acyl side chain and anomeric structure, as well as C2-N2 bond rotation, on CTI energetics. These studies show that aqueous solutions of GlcNAc-containing structures contain measurable amounts of both cis and trans amides, which may influence their biological properties.
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Affiliation(s)
- Xiaosong Hu
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA
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