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Characterization of opposing responses to phenol by Bacillus subtilis chemoreceptors. J Bacteriol 2022; 204:e0044121. [PMID: 35007157 DOI: 10.1128/jb.00441-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacillus subtilis employs ten chemoreceptors to move in response to chemicals in its environment. While the sensing mechanisms have been determined for many attractants, little is known about the sensing mechanisms for repellents. In this work, we investigated phenol chemotaxis in B. subtilis. Phenol is an attractant at low, micromolar concentrations, and a repellent at high, millimolar concentrations. McpA was found to be the principal chemoreceptor governing the repellent response to phenol and other related aromatic compounds. In addition, the chemoreceptors McpC and HemAT were found to govern the attractant response to phenol and related compounds. Using chemoreceptor chimeras, McpA was found to sense phenol using its signaling domain rather than its sensing domain. These observations were substantiated in vitro, where direct binding of phenol to the signaling domain of McpA was observed using saturation-transfer difference nuclear magnetic resonance. These results further advance our understanding of B. subtilis chemotaxis and further demonstrate that the signaling domain of B. subtilis chemoreceptors can directly sense chemoeffectors. IMPORTANCE Bacterial chemotaxis is commonly thought to employ a sensing mechanism involving the extracellular sensing domain of chemoreceptors. Some ligands, however, appear to be sensed by the signaling domain. Phenolic compounds, commonly found in soil and root exudates, provide environmental cues for soil microbes like Bacillus subtilis. We show that phenol is sensed both as an attractant and a repellent. While the mechanism for sensing phenol as an attractant is still unknown, we found that phenol is sensed as a repellent by the signaling domain of the chemoreceptor McpA. This study furthers our understanding of the unconventional sensing mechanisms employed by the B. subtilis chemotaxis pathway.
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2
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Biosynthesis of Galactan in Mycobacterium tuberculosis as a Viable TB Drug Target? Antibiotics (Basel) 2020; 9:antibiotics9010020. [PMID: 31935842 PMCID: PMC7168186 DOI: 10.3390/antibiotics9010020] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 12/27/2019] [Accepted: 01/02/2020] [Indexed: 12/21/2022] Open
Abstract
While target-based drug design has proved successful in several therapeutic areas, this approach has not yet provided compelling outcomes in the field of antibacterial agents. This statement remains especially true for the development of novel therapeutic interventions against tuberculosis, an infectious disease that is among the top ten leading causes of death globally. Mycobacterial galactan is an important component of the protective cell wall core of the tuberculosis pathogen and it could provide a promising target for the design of new drugs. In this review, we summarize the current knowledge on galactan biosynthesis in Mycobacterium tuberculosis, including landmark findings that led to the discovery and understanding of three key enzymes in this pathway: UDP-galactose mutase, and galactofuranosyl transferases GlfT1 and GlfT2. Moreover, we recapitulate the efforts aimed at their inhibition. The predicted common transition states of the three enzymes provide the lucrative possibility of multitargeting in pharmaceutical development, a favourable property in the mitigation of drug resistance. We believe that a tight interplay between target-based computational approaches and experimental methods will result in the development of original inhibitors that could serve as the basis of a new generation of drugs against tuberculosis.
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Bettencourt P, Müller J, Nicastri A, Cantillon D, Madhavan M, Charles PD, Fotso CB, Wittenberg R, Bull N, Pinpathomrat N, Waddell SJ, Stylianou E, Hill AVS, Ternette N, McShane H. Identification of antigens presented by MHC for vaccines against tuberculosis. NPJ Vaccines 2020; 5:2. [PMID: 31908851 PMCID: PMC6941960 DOI: 10.1038/s41541-019-0148-y] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Accepted: 11/25/2019] [Indexed: 11/09/2022] Open
Abstract
Mycobacterium tuberculosis (M.tb) is responsible for more deaths globally than any other pathogen. The only available vaccine, bacillus Calmette-Guérin (BCG), has variable efficacy throughout the world. A more effective vaccine is urgently needed. The immune response against tuberculosis relies, at least in part, on CD4+ T cells. Protective vaccines require the induction of antigen-specific CD4+ T cells via mycobacterial peptides presented by MHC class-II in infected macrophages. In order to identify mycobacterial antigens bound to MHC, we have immunoprecipitated MHC class-I and class-II complexes from THP-1 macrophages infected with BCG, purified MHC class-I and MHC class-II peptides and analysed them by liquid chromatography tandem mass spectrometry. We have successfully identified 94 mycobacterial peptides presented by MHC-II and 43 presented by MHC-I, from 76 and 41 antigens, respectively. These antigens were found to be highly expressed in infected macrophages. Gene ontology analysis suggests most of these antigens are associated with membranes and involved in lipid biosynthesis and transport. The sequences of selected peptides were confirmed by spectral match validation and immunogenicity evaluated by IFN-gamma ELISpot against peripheral blood mononuclear cell from volunteers vaccinated with BCG, M.tb latently infected subjects or patients with tuberculosis disease. Three antigens were expressed in viral vectors, and evaluated as vaccine candidates alone or in combination in a murine aerosol M.tb challenge model. When delivered in combination, the three candidate vaccines conferred significant protection in the lungs and spleen compared with BCG alone, demonstrating proof-of-concept for this unbiased approach to identifying new candidate antigens. Protective vaccines against Mycobacterium tuberculosis (M.tb), such as bacillus Calmette-Guérin (BCG), trigger strong CD4 T-cell responses specific to mycobacterium peptides, but their efficacy is variable. Paulo Bettencourt and colleagues now identify a set of mycobacterium peptides presented by BCG-infected macrophages via major compatibility complexes (MHC), and show that three of these antigens can be combined to formulate a vaccine that confers improved protection to Mtb infection in mice. After identifying 94 MHC-II-associated and 43 MHC-I-associated mycobacterium peptides, the researchers performed immunogenicity assays with peripheral blood mononuclear cells from BCG-vaccinated donors, latent Mtb-infected patients and patients with tuberculosis, and show that a set of these peptides was recognised by the immune cells, validating their potential as possible components for new Mtb vaccine formulations. These findings further support the value of immunopeptidomics for the identification of new antigens for effective vaccine alternatives.
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Affiliation(s)
| | - Julius Müller
- 1Jenner Institute, University of Oxford, Oxford, OX3 7DQ UK
| | - Annalisa Nicastri
- 2Target Discovery Institute, University of Oxford, Oxford, OX3 7FZ UK
| | - Daire Cantillon
- 3Department of Global Health and Infection, Brighton and Sussex Medical School, University of Sussex, Brighton, BN1 9PX UK
| | - Meera Madhavan
- 1Jenner Institute, University of Oxford, Oxford, OX3 7DQ UK
| | - Philip D Charles
- 2Target Discovery Institute, University of Oxford, Oxford, OX3 7FZ UK
| | - Carine B Fotso
- 1Jenner Institute, University of Oxford, Oxford, OX3 7DQ UK
| | | | - Naomi Bull
- 1Jenner Institute, University of Oxford, Oxford, OX3 7DQ UK
| | | | - Simon J Waddell
- 3Department of Global Health and Infection, Brighton and Sussex Medical School, University of Sussex, Brighton, BN1 9PX UK
| | | | | | - Nicola Ternette
- 1Jenner Institute, University of Oxford, Oxford, OX3 7DQ UK.,2Target Discovery Institute, University of Oxford, Oxford, OX3 7FZ UK
| | - Helen McShane
- 1Jenner Institute, University of Oxford, Oxford, OX3 7DQ UK
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Zhu C, Miller M, Lusskin N, Mahlich Y, Wang Y, Zeng Z, Bromberg Y. Fingerprinting cities: differentiating subway microbiome functionality. Biol Direct 2019; 14:19. [PMID: 31666099 PMCID: PMC6822482 DOI: 10.1186/s13062-019-0252-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Accepted: 10/02/2019] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Accumulating evidence suggests that the human microbiome impacts individual and public health. City subway systems are human-dense environments, where passengers often exchange microbes. The MetaSUB project participants collected samples from subway surfaces in different cities and performed metagenomic sequencing. Previous studies focused on taxonomic composition of these microbiomes and no explicit functional analysis had been done till now. RESULTS As a part of the 2018 CAMDA challenge, we functionally profiled the available ~ 400 subway metagenomes and built predictor for city origin. In cross-validation, our model reached 81% accuracy when only the top-ranked city assignment was considered and 95% accuracy if the second city was taken into account as well. Notably, this performance was only achievable if the similarity of distribution of cities in the training and testing sets was similar. To assure that our methods are applicable without such biased assumptions we balanced our training data to account for all represented cities equally well. After balancing, the performance of our method was slightly lower (76/94%, respectively, for one or two top ranked cities), but still consistently high. Here we attained an added benefit of independence of training set city representation. In testing, our unbalanced model thus reached (an over-estimated) performance of 90/97%, while our balanced model was at a more reliable 63/90% accuracy. While, by definition of our model, we were not able to predict the microbiome origins previously unseen, our balanced model correctly judged them to be NOT-from-training-cities over 80% of the time. Our function-based outlook on microbiomes also allowed us to note similarities between both regionally close and far-away cities. Curiously, we identified the depletion in mycobacterial functions as a signature of cities in New Zealand, while photosynthesis related functions fingerprinted New York, Porto and Tokyo. CONCLUSIONS We demonstrated the power of our high-speed function annotation method, mi-faser, by analysing ~ 400 shotgun metagenomes in 2 days, with the results recapitulating functional signals of different city subway microbiomes. We also showed the importance of balanced data in avoiding over-estimated performance. Our results revealed similarities between both geographically close (Ofa and Ilorin) and distant (Boston and Porto, Lisbon and New York) city subway microbiomes. The photosynthesis related functional signatures of NYC were previously unseen in taxonomy studies, highlighting the strength of functional analysis.
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Affiliation(s)
- Chengsheng Zhu
- Department of Biochemistry and Microbiology, Rutgers University, 76 Lipman Dr, New Brunswick, NJ, 08873, USA.
| | - Maximilian Miller
- Department of Biochemistry and Microbiology, Rutgers University, 76 Lipman Dr, New Brunswick, NJ, 08873, USA
- Computational Biology & Bioinformatics - i12 Informatics, Technical University of Munich (TUM), Boltzmannstrasse 3, 85748, Garching/Munich, Germany
- TUM Graduate School, Center of Doctoral Studies in Informatics and its Applications (CeDoSIA), Technische Universität München, 85748, Garching/Munich, Germany
| | - Nick Lusskin
- Department of Biochemistry and Microbiology, Rutgers University, 76 Lipman Dr, New Brunswick, NJ, 08873, USA
| | - Yannick Mahlich
- Department of Biochemistry and Microbiology, Rutgers University, 76 Lipman Dr, New Brunswick, NJ, 08873, USA
- Computational Biology & Bioinformatics - i12 Informatics, Technical University of Munich (TUM), Boltzmannstrasse 3, 85748, Garching/Munich, Germany
- TUM Graduate School, Center of Doctoral Studies in Informatics and its Applications (CeDoSIA), Technische Universität München, 85748, Garching/Munich, Germany
- Institute for Advanced Study, Technische Universität München, Lichtenbergstrasse 2 a, 85748, Garching, Germany
| | - Yanran Wang
- Department of Biochemistry and Microbiology, Rutgers University, 76 Lipman Dr, New Brunswick, NJ, 08873, USA
| | - Zishuo Zeng
- Department of Biochemistry and Microbiology, Rutgers University, 76 Lipman Dr, New Brunswick, NJ, 08873, USA
| | - Yana Bromberg
- Department of Biochemistry and Microbiology, Rutgers University, 76 Lipman Dr, New Brunswick, NJ, 08873, USA.
- Institute for Advanced Study, Technische Universität München, Lichtenbergstrasse 2 a, 85748, Garching, Germany.
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5
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Ota R, Okamoto Y, Vavricka CJ, Oka T, Matsunaga E, Takegawa K, Kiyota H, Izumi M. Chemo-enzymatic synthesis of p-nitrophenyl β-D-galactofuranosyl disaccharides from Aspergillus sp. fungal-type galactomannan. Carbohydr Res 2019; 473:99-103. [PMID: 30658252 DOI: 10.1016/j.carres.2019.01.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 01/10/2019] [Accepted: 01/10/2019] [Indexed: 11/28/2022]
Abstract
β-d-Galactofuranose (Galf) is a component of polysaccharides and glycoconjugates. There are few reports about the involvement of galactofuranosyltransferases and galactofuranosidases (Galf-ases) in the synthesis and degradation of galactofuranose-containing glycans. The cell walls of filamentous fungi in the genus Aspergillus include galactofuranose-containing polysaccharides and glycoconjugates, such as O-glycans, N-glycans, and fungal-type galactomannan, which are important for cell wall integrity. In this study, we investigated the synthesis of p-nitrophenyl β-d-galactofuranoside and its disaccharides by chemo-enzymatic methods including use of galactosidase. The key step was selective removal of the concomitant pyranoside by enzymatic hydrolysis to purify p-nitrophenyl β-d-galactofuranoside, a promising substrate for β-d-galactofuranosidase from Streptomyces species.
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Affiliation(s)
- Ryo Ota
- Graduate School of Environmental and Life Science, Okayama University, Tsushima-naka 1-1-1, Okayama, 700-8530, Japan
| | - Yumi Okamoto
- Graduate School of Environmental and Life Science, Okayama University, Tsushima-naka 1-1-1, Okayama, 700-8530, Japan
| | - Christopher J Vavricka
- Graduate School of Science, Technology and Innovation, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501, Japan
| | - Takuji Oka
- Department of Applied Microbial Technology, Faculty of Biotechnology and Life Science, Sojo University, Ikeda, 4-22-1, Kumamoto 860-0082, Japan
| | - Emiko Matsunaga
- Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University, Hakozaki 6-10-1, Fukuoka, 812-8581, Japan
| | - Kaoru Takegawa
- Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University, Hakozaki 6-10-1, Fukuoka, 812-8581, Japan
| | - Hiromasa Kiyota
- Graduate School of Environmental and Life Science, Okayama University, Tsushima-naka 1-1-1, Okayama, 700-8530, Japan
| | - Minoru Izumi
- Graduate School of Environmental and Life Science, Okayama University, Tsushima-naka 1-1-1, Okayama, 700-8530, Japan.
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Abstract
Actinobacteria is a group of diverse bacteria. Most species in this class of bacteria are filamentous aerobes found in soil, including the genus Streptomyces perhaps best known for their fascinating capabilities of producing antibiotics. These bacteria typically have a Gram-positive cell envelope, comprised of a plasma membrane and a thick peptidoglycan layer. However, there is a notable exception of the Corynebacteriales order, which has evolved a unique type of outer membrane likely as a consequence of convergent evolution. In this chapter, we will focus on the unique cell envelope of this order. This cell envelope features the peptidoglycan layer that is covalently modified by an additional layer of arabinogalactan . Furthermore, the arabinogalactan layer provides the platform for the covalent attachment of mycolic acids , some of the longest natural fatty acids that can contain ~100 carbon atoms per molecule. Mycolic acids are thought to be the main component of the outer membrane, which is composed of many additional lipids including trehalose dimycolate, also known as the cord factor. Importantly, a subset of bacteria in the Corynebacteriales order are pathogens of human and domestic animals, including Mycobacterium tuberculosis. The surface coat of these pathogens are the first point of contact with the host immune system, and we now know a number of host receptors specific to molecular patterns exposed on the pathogen's surface, highlighting the importance of understanding how the cell envelope of Actinobacteria is structured and constructed. This chapter describes the main structural and biosynthetic features of major components found in the actinobacterial cell envelopes and highlights the key differences between them.
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Affiliation(s)
- Kathryn C Rahlwes
- Department of Microbiology, University of Massachusetts, 639 North Pleasant Street, Amherst, MA, 01003, USA
| | - Ian L Sparks
- Department of Microbiology, University of Massachusetts, 639 North Pleasant Street, Amherst, MA, 01003, USA
| | - Yasu S Morita
- Department of Microbiology, University of Massachusetts, 639 North Pleasant Street, Amherst, MA, 01003, USA.
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Ati J, Colas C, Lafite P, Sweeney RP, Zheng RB, Lowary TL, Daniellou R. The LPG1x family from Leishmania major is constituted of rare eukaryotic galactofuranosyltransferases with unprecedented catalytic properties. Sci Rep 2018; 8:17566. [PMID: 30514885 PMCID: PMC6279836 DOI: 10.1038/s41598-018-35847-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Accepted: 11/09/2018] [Indexed: 12/15/2022] Open
Abstract
Galactofuranosyltransferases are poorly described enzymes despite their crucial role in the virulence and the pathogenicity of numerous microorganisms. These enzymes are considered as potential targets for therapeutic action. In addition to the only well-characterised prokaryotic GlfT2 from Mycobacterium tuberculosis, four putative genes in Leishmania major were previously described as potential galactofuranosyltransferases. In this study, we have cloned, over-expressed, purified and fully determined the kinetic parameters of these four eukaryotic enzymes, thus demonstrating their unique potency in catalysing the transfer of the galactofuranosyl moiety into acceptors. Their individual promiscuity revealed to be different, as some of them could efficiently use NDP-pyranoses as donor substrates in addition to the natural UDP-galactofuranose. Such results pave the way for the development of chemoenzymatic synthesis of furanosyl-containing glycoconjugates as well as the design of improved drugs against leishmaniasis.
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Affiliation(s)
- Jihen Ati
- Institut de Chimie Organique et Analytique, UMR CNRS 7311, Université d'Orléans, Rue de Chartres, BP6759, Orléans, Cedex 02, France
| | - Cyril Colas
- Institut de Chimie Organique et Analytique, UMR CNRS 7311, Université d'Orléans, Rue de Chartres, BP6759, Orléans, Cedex 02, France
| | - Pierre Lafite
- Institut de Chimie Organique et Analytique, UMR CNRS 7311, Université d'Orléans, Rue de Chartres, BP6759, Orléans, Cedex 02, France
| | - Ryan P Sweeney
- Alberta Glycomics Centre and Department of Chemistry, The University of Alberta, Edmonton, AB, T6G 2G2, Canada
| | - Ruixiang Blake Zheng
- Alberta Glycomics Centre and Department of Chemistry, The University of Alberta, Edmonton, AB, T6G 2G2, Canada
| | - Todd L Lowary
- Alberta Glycomics Centre and Department of Chemistry, The University of Alberta, Edmonton, AB, T6G 2G2, Canada
| | - Richard Daniellou
- Institut de Chimie Organique et Analytique, UMR CNRS 7311, Université d'Orléans, Rue de Chartres, BP6759, Orléans, Cedex 02, France.
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Kuhaudomlarp S, Walpole S, Stevenson CEM, Nepogodiev SA, Lawson DM, Angulo J, Field RA. Unravelling the Specificity of Laminaribiose Phosphorylase from Paenibacillus sp. YM-1 towards Donor Substrates Glucose/Mannose 1-Phosphate by Using X-ray Crystallography and Saturation Transfer Difference NMR Spectroscopy. Chembiochem 2018; 20:181-192. [PMID: 29856496 DOI: 10.1002/cbic.201800260] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Indexed: 12/13/2022]
Abstract
Glycoside phosphorylases (GPs) carry out a reversible phosphorolysis of carbohydrates into oligosaccharide acceptors and the corresponding sugar 1-phosphates. The reversibility of the reaction enables the use of GPs as biocatalysts for carbohydrate synthesis. Glycosyl hydrolase family 94 (GH94), which only comprises GPs, is one of the most studied GP families that have been used as biocatalysts for carbohydrate synthesis, in academic research and in industrial production. Understanding the mechanism of GH94 enzymes is a crucial step towards enzyme engineering to improve and expand the applications of these enzymes in synthesis. In this work with a GH94 laminaribiose phosphorylase from Paenibacillus sp. YM-1 (PsLBP), we have demonstrated an enzymatic synthesis of disaccharide 1 (β-d-mannopyranosyl-(1→3)-d-glucopyranose) by using a natural acceptor glucose and noncognate donor substrate α-mannose 1-phosphate (Man1P). To investigate how the enzyme recognises different sugar 1-phosphates, the X-ray crystal structures of PsLBP in complex with Glc1P and Man1P have been solved, providing the first molecular detail of the recognition of a noncognate donor substrate by GPs, which revealed the importance of hydrogen bonding between the active site residues and hydroxy groups at C2, C4, and C6 of sugar 1-phosphates. Furthermore, we used saturation transfer difference NMR spectroscopy to support crystallographic studies on the sugar 1-phosphates, as well as to provide further insights into the PsLBP recognition of the acceptors and disaccharide products.
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Affiliation(s)
- Sakonwan Kuhaudomlarp
- Department of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK
| | - Samuel Walpole
- School of Pharmacy, University of East Anglia, Norwich, NR4 7TJ, UK
| | - Clare E M Stevenson
- Department of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK
| | - Sergey A Nepogodiev
- Department of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK
| | - David M Lawson
- Department of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK
| | - Jesus Angulo
- School of Pharmacy, University of East Anglia, Norwich, NR4 7TJ, UK
| | - Robert A Field
- Department of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK
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Xue X, Zheng RB, Koizumi A, Han L, Klassen JS, Lowary TL. Synthetic polyprenol-pyrophosphate linked oligosaccharides are efficient substrates for mycobacterial galactan biosynthetic enzymes. Org Biomol Chem 2018; 16:1939-1957. [DOI: 10.1039/c8ob00316e] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Synthetic glycosyl polyprenol phosphates are substrates for enzymes required for cell wall assembly in mycobacteria, including the organism that causes tuberculosis.
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Affiliation(s)
- Xiaochao Xue
- Alberta Glycomics Centre and Department of Chemistry
- University of Alberta
- Edmonton
- Canada
| | - Ruixiang Blake Zheng
- Alberta Glycomics Centre and Department of Chemistry
- University of Alberta
- Edmonton
- Canada
| | - Akihiko Koizumi
- Alberta Glycomics Centre and Department of Chemistry
- University of Alberta
- Edmonton
- Canada
| | - Ling Han
- Alberta Glycomics Centre and Department of Chemistry
- University of Alberta
- Edmonton
- Canada
| | - John S. Klassen
- Alberta Glycomics Centre and Department of Chemistry
- University of Alberta
- Edmonton
- Canada
| | - Todd L. Lowary
- Alberta Glycomics Centre and Department of Chemistry
- University of Alberta
- Edmonton
- Canada
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10
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Katafuchi Y, Li Q, Tanaka Y, Shinozuka S, Kawamitsu Y, Izumi M, Ekino K, Mizuki K, Takegawa K, Shibata N, Goto M, Nomura Y, Ohta K, Oka T. GfsA is a β1,5-galactofuranosyltransferase involved in the biosynthesis of the galactofuran side chain of fungal-type galactomannan in Aspergillus fumigatus. Glycobiology 2017; 27:568-581. [DOI: 10.1093/glycob/cwx028] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Accepted: 03/24/2017] [Indexed: 01/01/2023] Open
Affiliation(s)
- Yukako Katafuchi
- Department of Applied Microbial Technology, Faculty of Biotechnology and Life Science, Sojo University, Ikeda 4-22-1, Kumamoto 860-0082, Japan
| | - Qiushi Li
- Department of Applied Microbial Technology, Faculty of Biotechnology and Life Science, Sojo University, Ikeda 4-22-1, Kumamoto 860-0082, Japan
| | - Yutaka Tanaka
- Department of Infection and Host Defense, Tohoku Medical and Pharmaceutical University, Komatsushima 4-4-1, Sendai 981-8558, Japan
| | - Saki Shinozuka
- Graduate School of Environmental and Life Science, Okayama University, Tsushimanaka 1-1-1, Okayama 700-8530, Japan
| | - Yohei Kawamitsu
- Department of Applied Microbial Technology, Faculty of Biotechnology and Life Science, Sojo University, Ikeda 4-22-1, Kumamoto 860-0082, Japan
| | - Minoru Izumi
- Graduate School of Environmental and Life Science, Okayama University, Tsushimanaka 1-1-1, Okayama 700-8530, Japan
| | - Keisuke Ekino
- Department of Applied Microbial Technology, Faculty of Biotechnology and Life Science, Sojo University, Ikeda 4-22-1, Kumamoto 860-0082, Japan
| | - Keiji Mizuki
- Department of Nanoscience, Faculty of Engineering, Sojo University, Ikeda 4-22-1, Kumamoto 860-0082, Japan
| | - Kaoru Takegawa
- Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University, Hakozaki 6-10-1, Fukuoka 812-8581, Japan
| | - Nobuyuki Shibata
- Department of Infection and Host Defense, Tohoku Medical and Pharmaceutical University, Komatsushima 4-4-1, Sendai 981-8558, Japan
| | - Masatoshi Goto
- Department of Applied Biochemistry and Food Science, Saga University, Honjo-machi 1, Saga 840-8502, Japan
| | - Yoshiyuki Nomura
- Department of Applied Microbial Technology, Faculty of Biotechnology and Life Science, Sojo University, Ikeda 4-22-1, Kumamoto 860-0082, Japan
| | - Kazuyoshi Ohta
- Department of Applied Microbial Technology, Faculty of Biotechnology and Life Science, Sojo University, Ikeda 4-22-1, Kumamoto 860-0082, Japan
| | - Takuji Oka
- Department of Applied Microbial Technology, Faculty of Biotechnology and Life Science, Sojo University, Ikeda 4-22-1, Kumamoto 860-0082, Japan
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11
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Bolívar BE, Welch JT. Studies of the Binding of Modest Modulators of the Human Enzyme, Sirtuin 6, by STD NMR. Chembiochem 2017; 18:931-940. [PMID: 28222243 DOI: 10.1002/cbic.201600655] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Indexed: 01/02/2023]
Abstract
Pyrazinamide (PZA), an essential constituent of short-course tuberculosis chemotherapy, binds weakly but selectively to Sirtuin 6 (SIRT6). Despite the structural similarities between nicotinamide (NAM), PZA, and pyrazinoic acid (POA), these inhibitors modulate SIRT6 by different mechanisms and through different binding sites, as suggested by saturation transfer difference (STD) NMR. Available experimental evidence, such as that derived from crystal structures and kinetic experiments, has been of only limited utility in elucidation of the mechanistic details of sirtuin inhibition by NAM or other inhibitors. For instance, crystallographic structural analysis of sirtuin binding sites does not help us understand important differences in binding affinities among sirtuins or capture details of such dynamic process. Hence, STD NMR was utilized throughout this study. Our results not only agreed with the binding kinetics experiments but also gave a qualitative insight into the binding process. The data presented herein suggested some details about the geometry of the binding epitopes of the ligands in solution with the apo- and holoenzyme. Recognition that SIRT6 is affected selectively by PZA, an established clinical agent, suggests that the rational development of more potent and selective NAM surrogates might be possible. These derivatives might be accessible by employing the malleability of this scaffold to assist in the identification by STD NMR of the motifs that interact with the apo- and holoenzymes in solution.
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Affiliation(s)
- Beatriz E Bolívar
- Department of Chemistry, University at Albany, 1400 Washington Avenue, Albany, NY, 12205, USA
| | - John T Welch
- Department of Chemistry, University at Albany, 1400 Washington Avenue, Albany, NY, 12205, USA
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12
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Wesener DA, Levengood MR, Kiessling LL. Comparing Galactan Biosynthesis in Mycobacterium tuberculosis and Corynebacterium diphtheriae. J Biol Chem 2016; 292:2944-2955. [PMID: 28039359 DOI: 10.1074/jbc.m116.759340] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2016] [Revised: 12/28/2016] [Indexed: 11/06/2022] Open
Abstract
The suborder Corynebacterineae encompasses species like Corynebacterium glutamicum, which has been harnessed for industrial production of amino acids, as well as Corynebacterium diphtheriae and Mycobacterium tuberculosis, which cause devastating human diseases. A distinctive component of the Corynebacterineae cell envelope is the mycolyl-arabinogalactan (mAG) complex. The mAG is composed of lipid mycolic acids, and arabinofuranose (Araf) and galactofuranose (Galf) carbohydrate residues. Elucidating microbe-specific differences in mAG composition could advance biotechnological applications and lead to new antimicrobial targets. To this end, we compare and contrast galactan biosynthesis in C. diphtheriae and M. tuberculosis In each species, the galactan is constructed from uridine 5'-diphosphate-α-d-galactofuranose (UDP-Galf), which is generated by the enzyme UDP-galactopyranose mutase (UGM or Glf). UGM and the galactan are essential in M. tuberculosis, but their importance in Corynebacterium species was not known. We show that small molecule inhibitors of UGM impede C. glutamicum growth, suggesting that the galactan is critical in corynebacteria. Previous cell wall analysis data suggest the galactan polymer is longer in mycobacterial species than corynebacterial species. To explore the source of galactan length variation, a C. diphtheriae ortholog of the M. tuberculosis carbohydrate polymerase responsible for the bulk of galactan polymerization, GlfT2, was produced, and its catalytic activity was evaluated. The C. diphtheriae GlfT2 gave rise to shorter polysaccharides than those obtained with the M. tuberculosis GlfT2. These data suggest that GlfT2 alone can influence galactan length. Our results provide tools, both small molecule and genetic, for probing and perturbing the assembly of the Corynebacterineae cell envelope.
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Affiliation(s)
| | - Matthew R Levengood
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706
| | - Laura L Kiessling
- From the Department of Biochemistry and .,Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706
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13
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Frédéric CJM, Tikad A, Fu J, Pan W, Zheng RB, Koizumi A, Xue X, Lowary TL, Vincent SP. Synthesis of Unprecedented Sulfonylated Phosphono-exo-Glycals Designed as Inhibitors of the Three Mycobacterial Galactofuranose Processing Enzymes. Chemistry 2016; 22:15913-15920. [PMID: 27628709 DOI: 10.1002/chem.201603161] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Indexed: 11/06/2022]
Abstract
This study reports a new methodology to synthesize exo-glycals bearing both a sulfone and a phosphonate. This synthetic strategy provides a way to generate exo-glycals displaying two electron-withdrawing groups and was applied to eight different carbohydrates from the furanose and pyranose series. The Z/E configurations of these tetrasubstituted enol ethers could be ascertained using NMR spectroscopic techniques. Deprotection of an exo-glycal followed by an UMP (uridine monophosphate) coupling generated two new UDP (uridine diphosphate)-galactofuranose analogues. These two Z/E isomers were evaluated as inhibitors of UGM, GlfT1, and GlfT2, the three mycobacterial galactofuranose processing enzymes. Molecule 46-(E) is the first characterized inhibitor of GlfT1 reported to date and was also found to efficiently inhibit UGM in a reversible manner. Interestingly, GlfT2 showed a better affinity for the (Z) isomer. The three enzymes studied in the present work are not only interesting because, mechanistically, they are still the topic of intense investigations, but also because they constitute very important targets for the development of novel antimycobacterial agents.
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Affiliation(s)
- Christophe J-M Frédéric
- University of Namur (UNamur), Département de Chimie, Laboratoire de Chimie Bio-Organique, rue de Bruxelles 61, 5000, Namur, Belgium
| | - Abdellatif Tikad
- University of Namur (UNamur), Département de Chimie, Laboratoire de Chimie Bio-Organique, rue de Bruxelles 61, 5000, Namur, Belgium
| | - Jian Fu
- University of Namur (UNamur), Département de Chimie, Laboratoire de Chimie Bio-Organique, rue de Bruxelles 61, 5000, Namur, Belgium
| | - Weidong Pan
- The Key Laboratory of Chemistry for Natural Products of Guizhou Province, Chinese Academy of Sciences, 202, Sha-chong South Road, Guiyang, 550002, P. R. China
| | - Ruixiang B Zheng
- Department of Chemistry and Alberta Glycomics Centre, University of Alberta, Gunning-Lemieux Chemistry Centre, 11227 Saskatchewan Drive, Edmonton, AB T6G 2G2, Canada
| | - Akihiko Koizumi
- Department of Chemistry and Alberta Glycomics Centre, University of Alberta, Gunning-Lemieux Chemistry Centre, 11227 Saskatchewan Drive, Edmonton, AB T6G 2G2, Canada
| | - Xiaochao Xue
- Department of Chemistry and Alberta Glycomics Centre, University of Alberta, Gunning-Lemieux Chemistry Centre, 11227 Saskatchewan Drive, Edmonton, AB T6G 2G2, Canada
| | - Todd L Lowary
- Department of Chemistry and Alberta Glycomics Centre, University of Alberta, Gunning-Lemieux Chemistry Centre, 11227 Saskatchewan Drive, Edmonton, AB T6G 2G2, Canada
| | - Stéphane P Vincent
- University of Namur (UNamur), Département de Chimie, Laboratoire de Chimie Bio-Organique, rue de Bruxelles 61, 5000, Namur, Belgium.
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14
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Poulin MB, Lowary TL. Chemical Insight into the Mechanism and Specificity of GlfT2, a Bifunctional Galactofuranosyltransferase from Mycobacteria. J Org Chem 2016; 81:8123-30. [PMID: 27557056 DOI: 10.1021/acs.joc.6b01501] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mycobacteria, including the human pathogen Mycobacterium tuberculosis, produce a complex cell wall structure that is essential to survival. A key component of this structure is a glycoconjugate, the mycolyl-arabinogalactan-peptidoglycan complex, which has at its core a galactan domain composed of galactofuranose (Galf) residues linked to peptidoglycan. Because galactan biosynthesis is essential for mycobacterial viability, compounds that interfere with this process are potential therapeutic agents for treating mycobacterial diseases, including tuberculosis. Galactan biosynthesis in mycobacteria involves two glycosyltransferases, GlfT1 and GlfT2, which have been the subject of increasing interest in recent years. This Synopsis summarizes efforts to characterize the mechanism and specificity of GlfT2, which is responsible for introducing the majority of the Galf residues into mycobacterial galactan.
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Affiliation(s)
- Myles B Poulin
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta , 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
| | - Todd L Lowary
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta , 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2G2, Canada
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15
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Marchetti R, Perez S, Arda A, Imberty A, Jimenez‐Barbero J, Silipo A, Molinaro A. "Rules of Engagement" of Protein-Glycoconjugate Interactions: A Molecular View Achievable by using NMR Spectroscopy and Molecular Modeling. ChemistryOpen 2016; 5:274-96. [PMID: 27547635 PMCID: PMC4981046 DOI: 10.1002/open.201600024] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Indexed: 12/20/2022] Open
Abstract
Understanding the dynamics of protein-ligand interactions, which lie at the heart of host-pathogen recognition, represents a crucial step to clarify the molecular determinants implicated in binding events, as well as to optimize the design of new molecules with therapeutic aims. Over the last decade, advances in complementary biophysical and spectroscopic methods permitted us to deeply dissect the fine structural details of biologically relevant molecular recognition processes with high resolution. This Review focuses on the development and use of modern nuclear magnetic resonance (NMR) techniques to dissect binding events. These spectroscopic methods, complementing X-ray crystallography and molecular modeling methodologies, will be taken into account as indispensable tools to provide a complete picture of protein-glycoconjugate binding mechanisms related to biomedicine applications against infectious diseases.
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Affiliation(s)
- Roberta Marchetti
- Department of Chemical SciencestUniversity of Napoli Federico IIVia Cintia 480126NapoliItaly
| | - Serge Perez
- Department Molecular Pharmacochemistry UMR 5063CNRS and University of GrenobleAlpes, BP 5338041 Grenoble cedex 9France
| | - Ana Arda
- Bizkaia Technological ParkCIC bioGUNEBuilding 801A-148160Derio-BizkaiaSpain
| | - Anne Imberty
- Centre de Recherche sur les CNRSand University of Grenoble Macromolécules Végétales, UPR 5301Alpes, BP 5338041Grenoble cedex 9France
| | | | - Alba Silipo
- Department of Chemical SciencestUniversity of Napoli Federico IIVia Cintia 480126NapoliItaly
| | - Antonio Molinaro
- Department of Chemical SciencestUniversity of Napoli Federico IIVia Cintia 480126NapoliItaly
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16
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Abstract
![]()
The cell surface (or cell wall) of bacteria is coated with carbohydrate
(or glycan) structures that play a number of important roles. These
include providing structural integrity, serving as a permeability
barrier to extracellular compounds (e.g., drugs) and modulating the
immune system of the host. Of interest to this Account is the cell
wall structure of mycobacteria. There are a host of different mycobacterial
species, some of which cause human disease. The most well-known is Mycobacterium tuberculosis, the causative agent of tuberculosis.
The mycobacterial cell wall is characterized by the presence of unusual
carbohydrate structures that fulfill the roles described above. However,
in many cases, a molecular-level understanding of how mycobacterial
cell wall glycans mediate these processes is lacking. Inspired
by a seminar he heard as a postdoctoral fellow, the author
began his independent research program with a focus on the chemical
synthesis of mycobacterial glycans. The goals were not only to develop
synthetic approaches to these unique structures but also to provide
molecules that could be used to probe their biological function. Initial
work addressed the preparation of fragments of two key polysaccharides,
arabinogalactan and lipoarabinomannan, which contain large numbers
of sugar residues in the furanose (five-membered) ring form. At the
time these investigations began, there were few methods reported for
the synthesis of oligosaccharides containing furanose rings. Thus,
early in the program, a major area of interest was methodology development,
particularly for the preparation of 1,2-cis-furanosides.
To solve this challenge, a range of conformationally restricted donors
have been developed, both in the author’s group and others,
which provide 1,2-cis-furanosidic linkages with high
stereoselectivity. These investigations were followed by application
of the developed
methods to the synthesis of a range of target molecules containing
arabinofuranose and galactofuranose residues. These molecules have
now found application in biochemical, immunological, and structural
biology investigations, which have shed light on their biosynthesis
and how these motifs are recognized by both the innate and adaptive
immune systems. More recently, attention has been directed toward
the synthesis
of another class of immunologically active mycobacterial cell wall
glycans, the extractable glycolipids. In this case, efforts have been
primarily on phenolic glycolipids, and the compounds synthesized have
been used to evaluate their ability to modulate cytokine release.
Over the past 20 years, the use of chemical synthesis to provide increasingly
complex glycan structures has provided significant benefit to the
burgeoning field of mycobacterial glycobiology. Through the efforts
of groups from around the globe, access to these compounds is now
possible via relatively straightforward methods. As the pool of mycobacterial
glycans continues to grow, so too will our understanding of their
role in disease, which will undoubtedly lead to new strategies to
prevent or treat mycobacterial infections.
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Affiliation(s)
- Todd L. Lowary
- Alberta Glycomics Centre
and Department of Chemistry, University of Alberta, Gunning−Lemieux
Chemistry Centre, Edmonton, Alberta T6G 2G2, Canada
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17
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Abstract
The cell surface (or cell wall) of bacteria is coated with carbohydrate (or glycan) structures that play a number of important roles. These include providing structural integrity, serving as a permeability barrier to extracellular compounds (e.g., drugs) and modulating the immune system of the host. Of interest to this Account is the cell wall structure of mycobacteria. There are a host of different mycobacterial species, some of which cause human disease. The most well-known is Mycobacterium tuberculosis, the causative agent of tuberculosis. The mycobacterial cell wall is characterized by the presence of unusual carbohydrate structures that fulfill the roles described above. However, in many cases, a molecular-level understanding of how mycobacterial cell wall glycans mediate these processes is lacking. Inspired by a seminar he heard as a postdoctoral fellow, the author began his independent research program with a focus on the chemical synthesis of mycobacterial glycans. The goals were not only to develop synthetic approaches to these unique structures but also to provide molecules that could be used to probe their biological function. Initial work addressed the preparation of fragments of two key polysaccharides, arabinogalactan and lipoarabinomannan, which contain large numbers of sugar residues in the furanose (five-membered) ring form. At the time these investigations began, there were few methods reported for the synthesis of oligosaccharides containing furanose rings. Thus, early in the program, a major area of interest was methodology development, particularly for the preparation of 1,2-cis-furanosides. To solve this challenge, a range of conformationally restricted donors have been developed, both in the author's group and others, which provide 1,2-cis-furanosidic linkages with high stereoselectivity. These investigations were followed by application of the developed methods to the synthesis of a range of target molecules containing arabinofuranose and galactofuranose residues. These molecules have now found application in biochemical, immunological, and structural biology investigations, which have shed light on their biosynthesis and how these motifs are recognized by both the innate and adaptive immune systems. More recently, attention has been directed toward the synthesis of another class of immunologically active mycobacterial cell wall glycans, the extractable glycolipids. In this case, efforts have been primarily on phenolic glycolipids, and the compounds synthesized have been used to evaluate their ability to modulate cytokine release. Over the past 20 years, the use of chemical synthesis to provide increasingly complex glycan structures has provided significant benefit to the burgeoning field of mycobacterial glycobiology. Through the efforts of groups from around the globe, access to these compounds is now possible via relatively straightforward methods. As the pool of mycobacterial glycans continues to grow, so too will our understanding of their role in disease, which will undoubtedly lead to new strategies to prevent or treat mycobacterial infections.
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Affiliation(s)
- Todd L Lowary
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta , Gunning-Lemieux Chemistry Centre, Edmonton, Alberta T6G 2G2, Canada
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18
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Aguirre C, Cala O, Krimm I. Overview of Probing Protein‐Ligand Interactions Using NMR. ACTA ACUST UNITED AC 2015; 81:17.18.1-17.18.24. [DOI: 10.1002/0471140864.ps1718s81] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Clémentine Aguirre
- Institut des Sciences Analytiques, UMR5280 CNRS, Ecole Nationale Supérieure de Lyon Villeurbanne France
| | - Olivier Cala
- Institut des Sciences Analytiques, UMR5280 CNRS, Ecole Nationale Supérieure de Lyon Villeurbanne France
| | - Isabelle Krimm
- Institut des Sciences Analytiques, UMR5280 CNRS, Ecole Nationale Supérieure de Lyon Villeurbanne France
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19
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Marchetti R, Molinaro A, Silipo A. NMR as a Tool to Unveil the Molecular Basis of Glycan-mediated Host–Pathogen Interactions. CARBOHYDRATES IN DRUG DESIGN AND DISCOVERY 2015. [DOI: 10.1039/9781849739993-00021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The nature of the relationship between microbes and hosts spans the broad spectrum from beneficial (symbiosis) to pathogenic (disease); one of the key factors determining the establishment of any type of host–microbe interaction is the pattern of glycoconjugates exposed on cell surfaces, many known as virulence factors since they are pivotal for adhesion to host tissue, immunoevasion and immunosuppression, causing disease in the host. The recognition of these pathogen glycostructures by specific host receptors is an important means of immune defense. In this context, NMR represents a valuable tool to investigate the conformational properties of both host/pathogen signaling molecules and to disclose their interaction at a molecular level. This chapter provides an overview of several protein–carbohydrate interaction systems studied by NMR, and their implications in human and plant diseases.
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Affiliation(s)
- Roberta Marchetti
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario Monte Sant’Angelo Via Cintia 4 I-80126 Napoli Italy
| | - Antonio Molinaro
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario Monte Sant’Angelo Via Cintia 4 I-80126 Napoli Italy
| | - Alba Silipo
- Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario Monte Sant’Angelo Via Cintia 4 I-80126 Napoli Italy
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20
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Ardá A, Canales A, Cañada FJ, Jiménez-Barbero J. Carbohydrate–Protein Interactions: A 3D View by NMR. CARBOHYDRATES IN DRUG DESIGN AND DISCOVERY 2015. [DOI: 10.1039/9781849739993-00001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
NMR spectroscopy is a key tool for carbohydrate research. In studies with complex oligosaccharides there are limits to the amount of relevant structural information provided by these observables due to problems of signal overlapping, strong coupling and/or the scarcity of the key NOE information. Thus, there is an increasing need for additional parameters with structural information, such as residual dipolar couplings (RDCs), paramagnetic relaxation enhancements (PREs) or pseudo contact shifts (PCSs). Carbohydrates are rather flexible molecules. Therefore, NMR observables do not always correlate with a single conformer but with an ensemble of low free-energy conformers that can be accessed by thermal fluctuations. Depending on the system under study, different NMR approaches can be followed to characterize protein–carbohydrate interactions: the standard methodologies can usually be classified as “ligand-based” or “receptor-based”. The selection of the proper methodology is usually determined by the size of the receptor, the dissociation constant of the complex (KD), the availability of the labelled protein (15N, 13C) and the access to soluble receptors at enough concentration for NMR measurements.
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Affiliation(s)
- Ana Ardá
- Chemical and Physical Biology, CIB-CSIC Ramiro de Maeztu 9 28040 Madrid Spain
| | - Angeles Canales
- Chemical and Physical Biology, CIB-CSIC Ramiro de Maeztu 9 28040 Madrid Spain
| | - F. Javier Cañada
- Chemical and Physical Biology, CIB-CSIC Ramiro de Maeztu 9 28040 Madrid Spain
| | - Jesús Jiménez-Barbero
- Chemical and Physical Biology, CIB-CSIC Ramiro de Maeztu 9 28040 Madrid Spain
- CIC bioGUNE, Parque Tecnológico de Bizkaia Edif. 801A-1 48160 Derio-Bizkaia Spain
- Ikerbasque, Basque Foundation for Science Bilbao Spain
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21
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Eppe G, El Bkassiny S, Vincent SP. Galactofuranose Biosynthesis: Discovery, Mechanisms and Therapeutic Relevance. CARBOHYDRATES IN DRUG DESIGN AND DISCOVERY 2015. [DOI: 10.1039/9781849739993-00209] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Galactofuranose, the atypical and thermodynamically disfavored form of d-galactose, has in reality a very old history in chemistry and biochemistry. The purpose of this book chapter is to give an overview on the fundamental aspects of the galactofuranose biosynthesis, from the biological occurrence to the search of inhibitors.
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Affiliation(s)
- Guillaume Eppe
- University of Namur, Département de Chimie, Laboratoire de Chimie Bio-Organique rue de Bruxelles 61 B-5000 Namur Belgium
| | - Sandy El Bkassiny
- University of Namur, Département de Chimie, Laboratoire de Chimie Bio-Organique rue de Bruxelles 61 B-5000 Namur Belgium
| | - Stéphane P. Vincent
- University of Namur, Département de Chimie, Laboratoire de Chimie Bio-Organique rue de Bruxelles 61 B-5000 Namur Belgium
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22
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Alderwick LJ, Harrison J, Lloyd GS, Birch HL. The Mycobacterial Cell Wall--Peptidoglycan and Arabinogalactan. Cold Spring Harb Perspect Med 2015; 5:a021113. [PMID: 25818664 DOI: 10.1101/cshperspect.a021113] [Citation(s) in RCA: 133] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The mycobacterial bacillus is encompassed by a remarkably elaborate cell wall structure. The mycolyl-arabinogalactan-peptidoglycan (mAGP) complex is essential for the viability of Mycobacterium tuberculosis and maintains a robust basal structure supporting the upper "myco-membrane." M. tuberculosis peptidoglycan, although appearing to be unexceptional at first glance, contains a number of unique molecular subtleties that become particularly important as the TB-bacilli enters into nonreplicative growth during dormancy. Arabinogalactan, a highly branched polysaccharide, serves to connect peptidoglycan with the outer mycolic acid layer, and a variety of unique glycolsyltransferases are used for its assembly. In this review, we shall explore the microbial chemistry of this unique heteropolysacchride, examine the molecular genetics that underpins its fabrication, and discuss how the essential biosynthetic process might be exploited for the development of future anti-TB chemotherapies.
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Affiliation(s)
- Luke J Alderwick
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - James Harrison
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Georgina S Lloyd
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Helen L Birch
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom
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23
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Dumitrescu L, Eppe G, Tikad A, Pan W, El Bkassiny S, Gurcha SS, Ardá A, Jiménez-Barbero J, Besra GS, Vincent SP. Selectfluor and NFSI exo-glycal fluorination strategies applied to the enhancement of the binding affinity of galactofuranosyltransferase GlfT2 inhibitors. Chemistry 2014; 20:15208-15. [PMID: 25251918 DOI: 10.1002/chem.201404180] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Indexed: 12/31/2022]
Abstract
Two complementary methods for the synthesis of fluorinated exo-glycals have been developed, for which previously no general reaction had been available. First, a Selectfluor-mediated fluorination was optimized after detailed analysis of all the reaction parameters. A dramatic effect of molecular sieves on the course of the reaction was observed. The reaction was generalized with a set of biologically relevant furanosides and pyranosides. A second direct approach involving carbanionic chemistry and the use of N-fluorobenzenesulfonimide (NFSI) was performed and this method gave better diastereoselectivities. Assignment of the Z/E configuration of all the fluorinated exo-glycals was achieved based on the results of HOESY experiments. Furthermore, fluorinated exo-glycal analogues of UDP-galactofuranose were prepared and assayed against GlfT2, which is a key enzyme involved in the cell-wall biosynthesis of major pathogens. The fluorinated exo-glycals proved to be potent inhibitors as compared with a series of C-glycosidic analogues of UDP-Galf, thus demonstrating the double beneficial effect of the exocyclic enol ether functionality and the fluorine atom.
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Affiliation(s)
- Lidia Dumitrescu
- University of Namur (UNamur), Département de Chimie, Laboratoire de Chimie Bio-Organique rue de Bruxelles 61, B-5000 Namur (Belgium), Fax: (+32) 81-72-45-17
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24
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Fechner P, Bleher O, Ewald M, Freudenberger K, Furin D, Hilbig U, Kolarov F, Krieg K, Leidner L, Markovic G, Proll G, Pröll F, Rau S, Riedt J, Schwarz B, Weber P, Widmaier J. Size does matter! Label-free detection of small molecule-protein interaction. Anal Bioanal Chem 2014; 406:4033-51. [PMID: 24817356 DOI: 10.1007/s00216-014-7834-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Revised: 04/07/2014] [Accepted: 04/11/2014] [Indexed: 11/28/2022]
Abstract
This review is focused on methods for detecting small molecules and, in particular, the characterisation of their interaction with natural proteins (e.g. receptors, ion channels). Because there are intrinsic advantages to using label-free methods over labelled methods (e.g. fluorescence, radioactivity), this review only covers label-free techniques. We briefly discuss available techniques and their advantages and disadvantages, especially as related to investigating the interaction between small molecules and proteins. The reviewed techniques include well-known and widely used standard analytical methods (e.g. HPLC-MS, NMR, calorimetry, and X-ray diffraction), newer and more specialised analytical methods (e.g. biosensors), biological systems (e.g. cell lines and animal models), and in-silico approaches.
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Affiliation(s)
- Peter Fechner
- Biametrics GmbH, Auf der Morgenstelle 18, 72076, Tübingen, Germany,
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25
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Chlubnová I, Králová B, Dvořáková H, Hošek P, Spiwok V, Filipp D, Nugier-Chauvin C, Daniellou R, Ferrières V. The versatile enzyme Araf51 allowed efficient synthesis of rare pathogen-related β-d-galactofuranosyl-pyranoside disaccharides. Org Biomol Chem 2014; 12:3080-9. [DOI: 10.1039/c3ob42519c] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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26
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Li J, Lowary TL. Sulfonium ions as inhibitors of the mycobacterial galactofuranosyltransferase GlfT2. MEDCHEMCOMM 2014. [DOI: 10.1039/c4md00067f] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The mycobacterial cell wall possesses a core galactan moiety composed of approximately 30 galactofuranosyl residues attached via alternating β-(1→5) and β-(1→6) linkages.
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Affiliation(s)
- Jing Li
- Alberta Glycomics Centre and Department of Chemistry
- The University of Alberta
- Gunning–Lemieux Chemistry Centre
- Edmonton
- Canada
| | - Todd L. Lowary
- Alberta Glycomics Centre and Department of Chemistry
- The University of Alberta
- Gunning–Lemieux Chemistry Centre
- Edmonton
- Canada
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27
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NMR-based analysis of protein-ligand interactions. Anal Bioanal Chem 2013; 406:943-56. [PMID: 23591643 DOI: 10.1007/s00216-013-6931-0] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Revised: 03/12/2013] [Accepted: 03/19/2013] [Indexed: 10/27/2022]
Abstract
Physiological processes are mainly controlled by intermolecular recognition mechanisms involving protein-protein and protein-ligand (low molecular weight molecules) interactions. One of the most important tools for probing these interactions is high-field solution nuclear magnetic resonance (NMR) through protein-observed and ligand-observed experiments, where the protein receptor or the organic compounds are selectively detected. NMR binding experiments rely on comparison of NMR parameters of the free and bound states of the molecules. Ligand-observed methods are not limited by the protein molecular size and therefore have great applicability for analysing protein-ligand interactions. The use of these NMR techniques has considerably expanded in recent years, both in chemical biology and in drug discovery. We review here three major ligand-observed NMR methods that depend on the nuclear Overhauser effect-transferred nuclear Overhauser effect spectroscopy, saturation transfer difference spectroscopy and water-ligand interactions observed via gradient spectroscopy experiments-with the aim of reporting recent developments and applications for the characterization of protein-ligand complexes, including affinity measurements and structural determination.
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Liu C, Kang H, Wightman RH, Jiang S. Stereoselective synthesis of a novel Galf-disaccharide mimic: β-d-galactofuranosyl-(1-5)-β-d-galactofuranosyl motif of mycobacterial cell walls. Tetrahedron Lett 2013. [DOI: 10.1016/j.tetlet.2012.12.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Marino C, Lima C, Mariño K, de Lederkremer RM. Synthesis of a derivative of α-D-Glcp(1->2)-D-Galf suitable for further glycosylation and of α-D-Glcp(1->2)-D-Gal, a disaccharide fragment obtained from varianose. Beilstein J Org Chem 2012; 8:2142-8. [PMID: 23243476 PMCID: PMC3520571 DOI: 10.3762/bjoc.8.241] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Accepted: 11/22/2012] [Indexed: 11/23/2022] Open
Abstract
The presence of galactofuranoyl units in infectious microorganisms has prompted the study of the metabolic pathways involved in their incorporation in glycans. Although much progress has been made with respect to the biosynthesis of β-D-Galf-containing glycoconjugates, the mechanisms by which α-D-Galf units are incorporated remain unclear. Penicillium varians is a non-pathogenic fungus that produces varianose, a polysaccharide containing both α- and β-D-Galf units, which can be used as a model for biosynthetic studies on α-D-Galf incorporation. Synthetic oligosaccharide fragments related to varianose are useful as potential substrates or standards for characterization of the α-galactofuranosyl transferases. In this paper we report a straightforward procedure for the synthesis of α-D-Glcp(1→2)-D-Gal (1) and the use of this compound to monitor the natural disaccharide released from varianose by mild acid degradation. The synthesis, performed by the glycosylaldonolactone approach, involved a glucosylgalactofuranose derivative, suitable for the synthesis of higher oligosaccharides with an internal D-Galf.
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Affiliation(s)
- Carla Marino
- CIHIDECAR-CONICET-UBA, Departamento de Química Orgánica, Facultad de Ciencias Exactas y Naturales, UBA, Buenos Aires (1428), Argentina
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Wheatley RW, Zheng RB, Richards MR, Lowary TL, Ng KKS. Tetrameric structure of the GlfT2 galactofuranosyltransferase reveals a scaffold for the assembly of mycobacterial Arabinogalactan. J Biol Chem 2012; 287:28132-43. [PMID: 22707726 DOI: 10.1074/jbc.m112.347484] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Biosynthesis of the mycobacterial cell wall relies on the activities of many enzymes, including several glycosyltransferases (GTs). The polymerizing galactofuranosyltransferase GlfT2 (Rv3808c) synthesizes the bulk of the galactan portion of the mycolyl-arabinogalactan complex, which is the largest component of the mycobacterial cell wall. We used x-ray crystallography to determine the 2.45-Å resolution crystal structure of GlfT2, revealing an unprecedented multidomain structure in which an N-terminal β-barrel domain and two primarily α-helical C-terminal domains flank a central GT-A domain. The kidney-shaped protomers assemble into a C(4)-symmetric homotetramer with an open central core and a surface containing exposed hydrophobic and positively charged residues likely involved with membrane binding. The structure of a 3.1-Å resolution complex of GlfT2 with UDP reveals a distinctive mode of nucleotide recognition. In addition, models for the binding of UDP-galactofuranose and acceptor substrates in combination with site-directed mutagenesis and kinetic studies suggest a mechanism that explains the unique ability of GlfT2 to generate alternating β-(1→5) and β-(1→6) glycosidic linkages using a single active site. The topology imposed by docking a tetrameric assembly onto a membrane bilayer also provides novel insights into aspects of processivity and chain length regulation in this and possibly other polymerizing GTs.
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Affiliation(s)
- Robert W Wheatley
- Alberta Glycomics Centre, University of Calgary, Calgary, Alberta T2N 1N4, Canada
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31
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Poulin MB, Zhou R, Lowary TL. Synthetic UDP-galactofuranose analogs reveal critical enzyme-substrate interactions in GlfT2-catalyzed mycobacterial galactan assembly. Org Biomol Chem 2012; 10:4074-87. [PMID: 22499274 DOI: 10.1039/c2ob25159k] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Mycobacterial cell wall galactan, composed of alternating β-(1→5) and β-(1→6) galactofuranosyl residues, is assembled by the action of two bifunctional galactofuranosyltransferases, GlfT1 and GlfT2, which use UDP-galactofuranose (UDP-Galf) as the donor substrate. Kinetic analysis of synthetic UDP-Galf analogs identified critical interactions involved in donor substrate recognition by GlfT2, a processive polymerizing glycosyltransferase. Testing of methylated UDP-Galf analogs showed the donor substrate-binding pocket is sterically crowded. Evaluation of deoxy UDP-Galf analogs revealed that the C-6 hydroxyl group is not essential for substrate activity, and that interactions with the UDP-Galf C-3 hydroxyl group orient the substrate for turnover but appears to play no role in substrate recognition, making the 3-deoxy-analog a moderate competitive inhibitor of the enzyme. Moreover, the addition of a Galf residue deoxygenated at C-5 or C-6, or an l-arabinofuranose residue, to the growing galactan chain resulted in "dead end" reaction products, which no longer act as an acceptor for the enzyme. This finding shows dual recognition of both the terminal C-5 and C-6 hydroxyl groups of the acceptor substrate are required for GlfT2 activity, which is consistent with a recent model developed based upon a crystal structure of the enzyme. These observations provide insight into specific protein-carbohydrate interactions in the GlfT2 active site and may facilitate the design of future inhibitors.
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Affiliation(s)
- Myles B Poulin
- Alberta Glycomics Centre and Department of Chemistry, Gunning-Lemieux Chemistry Centre, University of Alberta, Edmonton, AB T6G 2G2, Canada
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Chlubnova I, Legentil L, Dureau R, Pennec A, Almendros M, Daniellou R, Nugier-Chauvin C, Ferrières V. Specific and non-specific enzymes for furanosyl-containing conjugates: biosynthesis, metabolism, and chemo-enzymatic synthesis. Carbohydr Res 2012; 356:44-61. [PMID: 22554502 DOI: 10.1016/j.carres.2012.04.002] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2012] [Revised: 04/02/2012] [Accepted: 04/03/2012] [Indexed: 11/27/2022]
Abstract
There is no doubt now that the synthesis of compounds of varying complexity such as saccharides and derivatives thereof continuously grows with enzymatic methods. This review focuses on recent basic knowledge on enzymes specifically involved in the biosynthesis and degradation of furanosyl-containing polysaccharides and conjugates. Moreover, and when possible, biocatalyzed approaches, alternative to standard synthesis, will be detailed in order to strengthen the high potential of these biocatalysts to go further with the preparation of rare furanosides. Interesting results will be also proposed with chemo-enzymatic processes based on nonfuranosyl-specific enzymes.
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Affiliation(s)
- Ilona Chlubnova
- Ecole Nationale Supérieure de Chimie de Rennes, CNRS, UMR 6226, Avenue du Général Leclerc, CS 50837, 35708 Rennes Cedex 7, France
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May JF, Levengood MR, Splain RA, Brown CD, Kiessling LL. A processive carbohydrate polymerase that mediates bifunctional catalysis using a single active site. Biochemistry 2012; 51:1148-59. [PMID: 22217153 DOI: 10.1021/bi201820p] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Even in the absence of a template, glycosyltransferases can catalyze the synthesis of carbohydrate polymers of specific sequence. The paradigm has been that one enzyme catalyzes the formation of one type of glycosidic linkage, yet certain glycosyltransferases generate polysaccharide sequences composed of two distinct linkage types. In principle, bifunctional glycosyltransferases can possess separate active sites for each catalytic activity or one active site with dual activities. We encountered the fundamental question of one or two distinct active sites in our investigation of the galactosyltransferase GlfT2. GlfT2 catalyzes the formation of mycobacterial galactan, a critical cell-wall polymer composed of galactofuranose residues connected with alternating, regioisomeric linkages. We found that GlfT2 mediates galactan polymerization using only one active site that manifests dual regioselectivity. Structural modeling of the bifunctional glycosyltransferases hyaluronan synthase and cellulose synthase suggests that these enzymes also generate multiple glycosidic linkages using a single active site. These results highlight the versatility of glycosyltransferases for generating polysaccharides of specific sequence. We postulate that a hallmark of processive elongation of a carbohydrate polymer by a bifunctional enzyme is that one active site can give rise to two separate types of glycosidic bonds.
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Affiliation(s)
- John F May
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706-1544, United States
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34
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Gannabathula S, Skinner MA, Rosendale D, Greenwood JM, Mutukumira AN, Steinhorn G, Stephens J, Krissansen GW, Schlothauer RC. Arabinogalactan proteins contribute to the immunostimulatory properties of New Zealand honeys. Immunopharmacol Immunotoxicol 2012; 34:598-607. [DOI: 10.3109/08923973.2011.641974] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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35
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Carbasugar Analogues of Galactofuranosides: Pseudodisaccharide Mimics of Fragments of Mycobacterial Arabinogalactan. European J Org Chem 2011. [DOI: 10.1002/ejoc.201001380] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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36
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Maurer T. Advancing fragment binders to lead-like compounds using ligand and protein-based NMR spectroscopy. Methods Enzymol 2011; 493:469-85. [PMID: 21371602 DOI: 10.1016/b978-0-12-381274-2.00018-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The application of NMR in fragment-based lead discovery (FBLD) has quickly developed from a sensitive method for the identification of low-affinity binders to an important tool in the hit-to-lead process. NMR can play a constructive role in the process from identifying those fragments with the best potential toward a biochemically active compound to developing them into molecules with high affinity and selectivity to a given target protein. NMR hit-to-lead involves revising the lead identification process at the beginning of a fragment-based drug discovery project, the primary screen, and also looking toward protein-detected NMR methods in advancing compounds from fragment hit into and through fragment hit-to-lead. With the development of higher sensitivity cold NMR probes, ligand-based NMR methods can be successfully applied to a majority of projects found in a pharmaceutical pipeline. Having matured from the original concepts such as SAR by NMR (Shuker, S. B., Hajduk, P. J., Meadows, R. P., Fesik, S. W. (1996) Discovering high-affinity ligands for proteins: SAR by NMR. Science274 (5292), 1531-1534.), projects that base their lead matter on fragment hits are close to or already in the clinic (Woodhead, A. J., Angove, H., Carr, M. G., Chessari, G., Congreve, M., Coyle, J. E., Cosme, J., Graham, B., Day, P. J., Downham, R., Fazal, L., Feltell, R., et al. (2010) discovery of (2,4-dihydroxy-5-isopropylphenyl)-[5-(4-methylpiperazin-1-ylmethyl)-1,3-dihydroisoindol-2-yl]methanone (AT13387), a novel inhibitor of the molecular chaperone Hsp90 by fragment based drug design. J. Med. Chem.53, 5956-5969, Chessari, G., and Woodhead, A. J. (2009). From fragment to clinical candidate: A historical perspective. Drug Discov. Today14 (13-14), 668-675.). Generating new ideas toward new binding modes and mechanisms of action as well as new intellectual property will be the standard by which the success of FBLD will need to be measured. A strategy outlining the various steps involved in NMR hit-to-lead is provided. By means of a specific example, the workflow is described to guide the reader through the experimental setup.
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Affiliation(s)
- Till Maurer
- Department of Structural Biology, Genentech Inc., South San Francisco, California, USA
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37
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Xia Y, Zhu Q, Jun KY, Wang J, Gao X. Clean STD-NMR spectrum for improved detection of ligand-protein interactions at low concentration of protein. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2010; 48:918-924. [PMID: 20957656 DOI: 10.1002/mrc.2687] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Saturation transfer difference (STD)-NMR has been widely used to screen ligand compound libraries for their binding activities to proteins and to determine the binding epitopes of the ligands. We report herein, a Clean STD-NMR method developed to overcome false positives (artifacts) observed in the STD-NMR spectrum due to the power spillover of RF irradiation. The method achieved higher degree of resonance saturation through digital editing of two STD-NMR spectra to generate a concatenated difference spectrum and three times of sensitivity enhancement for a loose binding complex involving DNA oligonucleotide and an RNA-binding protein, CUGBP-1ab (25.2 kDa). The interesting binding characteristics of the complex dCTGTCT-CUGBP1ab were obtained. The method was applied to a mixture of small ligand and bovine serum albumin protein (BSA, 66.3 kDa), and detected the intermolecular contacts at a BSA concentration as low as 0.1 µM, a working concentration useful for the detection of proteins of low solubility at biologically relevant conditions.
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Affiliation(s)
- Youlin Xia
- Department of Biology and Biochemistry, University of Houston, Houston, TX 77004, USA.
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Angulo J, Enríquez-Navas PM, Nieto PM. Ligand-receptor binding affinities from saturation transfer difference (STD) NMR spectroscopy: the binding isotherm of STD initial growth rates. Chemistry 2010; 16:7803-12. [PMID: 20496354 DOI: 10.1002/chem.200903528] [Citation(s) in RCA: 134] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The direct evaluation of dissociation constants (K(D)) from the variation of saturation transfer difference (STD) NMR spectroscopy values with the receptor-ligand ratio is not feasible due to the complex dependence of STD intensities on the spectral properties of the observed signals. Indirect evaluation, by competition experiments, allows the determination of K(D), as long as a ligand of known affinity is available for the protein under study. Herein, we present a novel protocol based on STD NMR spectroscopy for the direct measurements of receptor-ligand dissociation constants (K(D)) from single-ligand titration experiments. The influence of several experimental factors on STD values has been studied in detail, confirming the marked impact on standard determinations of protein-ligand affinities by STD NMR spectroscopy. These factors, namely, STD saturation time, ligand residence time in the complex, and the intensity of the signal, affect the accumulation of saturation in the free ligand by processes closely related to fast protein-ligand rebinding and longitudinal relaxation of the ligand signals. The proposed method avoids the dependence of the magnitudes of ligand STD signals at a given saturation time on spurious factors by constructing the binding isotherms using the initial growth rates of the STD amplification factors, in a similar way to the use of NOE growing rates to estimate cross relaxation rates for distance evaluations. Herein, it is demonstrated that the effects of these factors are cancelled out by analyzing the protein-ligand association curve using STD values at the limit of zero saturation time, when virtually no ligand rebinding or relaxation takes place. The approach is validated for two well-studied protein-ligand systems: the binding of the saccharides GlcNAc and GlcNAcbeta1,4GlcNAc (chitobiose) to the wheat germ agglutinin (WGA) lectin, and the interaction of the amino acid L-tryptophan to bovine serum albumin (BSA). In all cases, the experimental K(D) measured under different experimental conditions converged to the thermodynamic values. The proposed protocol allows accurate determinations of protein-ligand dissociation constants, extending the applicability of the STD NMR spectroscopy for affinity measurements, which is of particular relevance for those proteins for which a ligand of known affinity is not available.
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Affiliation(s)
- Jesús Angulo
- Department of Bioorganic Chemistry, Instituto de Investigaciones Químicas (CSIC-US), Américo Vespucio 49, 41092, Sevilla, Spain.
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Szczepina MG, Zheng RB, Completo GC, Lowary TL, Pinto BM. STD-NMR studies of two acceptor substrates of GlfT2, a galactofuranosyltransferase from Mycobacterium tuberculosis: epitope mapping studies. Bioorg Med Chem 2010; 18:5123-8. [PMID: 20591680 DOI: 10.1016/j.bmc.2010.05.069] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2010] [Revised: 05/23/2010] [Accepted: 05/25/2010] [Indexed: 10/19/2022]
Abstract
The major structural component of the mycobacterial cell wall, the mycolyl-arabinogalactan-peptidoglycan complex, possesses a galactan core composed of approximately 30 galactofuranosyl (Galf) resides attached via alternating beta-(1-->6) and beta-(1-->5) linkages. Recent studies have shown that the entire galactan is synthesized by two bifunctional galactofuranosyltransferases, GlfT1 and GlfT2. We report here saturation transfer difference (STD) NMR studies GlfT2 using two trisaccharide acceptor substrates, beta-D-Galf-(1-->6)-beta-D-Galf-(1-->5)-beta-D-Galf-O(CH2)7CH3 (2) and beta-D-Galf-(1-->5)-beta-D-Galf-(1-->6)-beta-D-Galf-O(CH2)7CH3 (3), as well as the donor substrate for the enzyme, UDP-Galf. Epitope mapping demonstrated a greater enhancement toward the 'reducing' ends of both trisaccharides, and that UDP-galactofuranose (UDP-Galf) made more intimate contacts through its nucleotide moiety. This observation is consistent with the greater flexibility required within the active site of the reaction between the growing polymer acceptor and the UDP-Galf donor. The addition of UDP-Galf to either 2 or 3 in the presence of GlfT2 generated a tetrasaccharide product, indicating that the enzyme was catalytically active.
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Affiliation(s)
- Monica G Szczepina
- Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
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Dureau R, Robert-Gangneux F, Gangneux JP, Nugier-Chauvin C, Legentil L, Daniellou R, Ferrières V. Synthetic UDP-furanoses inhibit the growth of the parasite Leishmania. Carbohydr Res 2010; 345:1299-305. [PMID: 20303072 DOI: 10.1016/j.carres.2010.02.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2010] [Revised: 02/11/2010] [Accepted: 02/20/2010] [Indexed: 11/28/2022]
Abstract
The chemical synthesis of UDP-6-NHAc-6-deoxy-Galf was performed and it led to the isolation of both pure anomers. They were then evaluated together with the previously prepared UDP-furanoses for their anti-parasitic properties against Leishmania donovani promastigotes, one of the agents responsible for visceral leishmaniasis. Amongst them, the unnatural 1,2-trans UDP-6-NHAc-Galf demonstrated a high potency in inhibiting the growth of the parasite.
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Affiliation(s)
- Rémy Dureau
- Ecole Nationale Supérieure de Chimie de Rennes, CNRS, UMR 6226, Avenue du Général Leclerc, CS 50837, 35708 Rennes Cedex 7, France
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Abstract
Carbohydrates in the thermodynamically disfavored furanose ring conformation are not present in mammalian glycoconjugates, but are widespread in the glycans produced by many bacterial pathogens. In bacteria, these furanose sugars are often found in cell surface glycoconjugates, and are essential for the viability or virulence of the organisms. As a result, the enzymes involved in the biosynthesis of bacterial furanosides are attractive targets as potential selective antimicrobial chemotherapeutics. However, before such chemotherapeutics can be designed, synthesized, and evaluated, more information about the activity and specificity of these enzymes is required. This chapter describes assays that have been used to study enzymes involved in the biosynthesis of one of the most abundant naturally occurring furanose residues, galactofuranose (Galf). In particular, the focus is on UDP-galactopyranose mutase and galactofuranosyltransferases. The assays described in this chapter require UDP-galactofuranose (UDP-Galf); therefore, a procedure for the preparation of UDP-Galf, as well as various UDP-Galf derivatives, using a three-enzyme chemoenzymatic procedure, is also described.
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Affiliation(s)
- Myles B Poulin
- The Alberta Ingenuity Centre for Carbohydrate Science, Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada
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