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Bashiri G, Bulloch EMM, Bramley WR, Davidson M, Stuteley SM, Young PG, Harris PWR, Naqvi MSH, Middleditch MJ, Schmitz M, Chang WC, Baker EN, Squire CJ. Poly-γ-glutamylation of biomolecules. Nat Commun 2024; 15:1310. [PMID: 38346985 PMCID: PMC10861534 DOI: 10.1038/s41467-024-45632-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Accepted: 01/24/2024] [Indexed: 02/15/2024] Open
Abstract
Poly-γ-glutamate tails are a distinctive feature of archaeal, bacterial, and eukaryotic cofactors, including the folates and F420. Despite decades of research, key mechanistic questions remain as to how enzymes successively add glutamates to poly-γ-glutamate chains while maintaining cofactor specificity. Here, we show how poly-γ-glutamylation of folate and F420 by folylpolyglutamate synthases and γ-glutamyl ligases, non-homologous enzymes, occurs via processive addition of L-glutamate onto growing γ-glutamyl chain termini. We further reveal structural snapshots of the archaeal γ-glutamyl ligase (CofE) in action, crucially including a bulged-chain product that shows how the cofactor is retained while successive glutamates are added to the chain terminus. This bulging substrate model of processive poly-γ-glutamylation by terminal extension is arguably ubiquitous in such biopolymerisation reactions, including addition to folates, and demonstrates convergent evolution in diverse species from archaea to humans.
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Affiliation(s)
- Ghader Bashiri
- School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand.
- Maurice Wilkins Center for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand.
| | - Esther M M Bulloch
- School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand
- Maurice Wilkins Center for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand
| | - William R Bramley
- School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand
| | - Madison Davidson
- Department of Chemistry, North Carolina State University, Raleigh, NC, 27695, USA
| | - Stephanie M Stuteley
- School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand
- Maurice Wilkins Center for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand
| | - Paul G Young
- School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand
- Maurice Wilkins Center for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand
| | - Paul W R Harris
- School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand
- Maurice Wilkins Center for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand
| | - Muhammad S H Naqvi
- School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand
| | - Martin J Middleditch
- School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand
| | - Michael Schmitz
- School of Chemical Sciences, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand
| | - Wei-Chen Chang
- Department of Chemistry, North Carolina State University, Raleigh, NC, 27695, USA
| | - Edward N Baker
- School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand
- Maurice Wilkins Center for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand
| | - Christopher J Squire
- School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand.
- Maurice Wilkins Center for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland, 1142, New Zealand.
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2
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Kordus SL, Baughn AD. Revitalizing antifolates through understanding mechanisms that govern susceptibility and resistance. MEDCHEMCOMM 2019; 10:880-895. [PMID: 31303985 PMCID: PMC6595967 DOI: 10.1039/c9md00078j] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Accepted: 05/07/2019] [Indexed: 12/12/2022]
Abstract
In prokaryotes and eukaryotes, folate (vitamin B9) is an essential metabolic cofactor required for all actively growing cells. Specifically, folate serves as a one-carbon carrier in the synthesis of amino acids (such as methionine, serine, and glycine), N-formylmethionyl-tRNA, coenzyme A, purines and thymidine. Many microbes are unable to acquire folates from their environment and rely on de novo folate biosynthesis. In contrast, mammals lack the de novo folate biosynthesis pathway and must obtain folate from commensal microbiota or the environment using proton-coupled folate transporters. The essentiality and dichotomy between mammalian and bacterial folate biosynthesis and utilization pathways make it an ideal drug target for the development of antimicrobial agents and cancer chemotherapeutics. In this minireview, we discuss general aspects of folate biosynthesis and the underlying mechanisms that govern susceptibility and resistance of organisms to antifolate drugs.
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Affiliation(s)
- Shannon Lynn Kordus
- Department of Microbiology and Immunology , University of Minnesota , Minneapolis , MN , USA .
| | - Anthony David Baughn
- Department of Microbiology and Immunology , University of Minnesota , Minneapolis , MN , USA .
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3
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Folate biosynthesis pathway: mechanisms and insights into drug design for infectious diseases. Future Med Chem 2018; 10:935-959. [PMID: 29629843 DOI: 10.4155/fmc-2017-0168] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Folate pathway is a key target for the development of new drugs against infectious diseases since the discovery of sulfa drugs and trimethoprim. The knowledge about this pathway has increased in the last years and the catalytic mechanism and structures of all enzymes of the pathway are fairly understood. In addition, differences among enzymes from prokaryotes and eukaryotes could be used for the design of specific inhibitors. In this review, we show a panorama of progress that has been achieved within the folate pathway obtained in the last years. We explored the structure and mechanism of enzymes, several genetic features, strategies, and approaches used in the design of new inhibitors that have been used as targets in pathogen chemotherapy.
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4
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Ramakrishnan G, Chandra NR, Srinivasan N. Recognizing drug targets using evolutionary information: implications for repurposing FDA-approved drugs against Mycobacterium tuberculosis H37Rv. MOLECULAR BIOSYSTEMS 2016; 11:3316-31. [PMID: 26429199 DOI: 10.1039/c5mb00476d] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Drug repurposing to explore target space has been gaining pace over the past decade with the upsurge in the use of systematic approaches for computational drug discovery. Such a cost and time-saving approach gains immense importance for pathogens of special interest, such as Mycobacterium tuberculosis H37Rv. We report a comprehensive approach to repurpose drugs, based on the exploration of evolutionary relationships inferred from the comparative sequence and structural analyses between targets of FDA-approved drugs and the proteins of M. tuberculosis. This approach has facilitated the identification of several polypharmacological drugs that could potentially target unexploited M. tuberculosis proteins. A total of 130 FDA-approved drugs, originally intended against other diseases, could be repurposed against 78 potential targets in M. tuberculosis. Additionally, we have also made an attempt to augment the chemical space by recognizing compounds structurally similar to FDA-approved drugs. For three of the attractive cases we have investigated the probable binding modes of the drugs in their corresponding M. tuberculosis targets by means of structural modelling. Such prospective targets and small molecules could be prioritized for experimental endeavours, and could significantly influence drug-discovery and drug-development programmes for tuberculosis.
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Affiliation(s)
- Gayatri Ramakrishnan
- Indian Institute of Science Mathematics Initiative, Indian Institute of Science, Bangalore-560012, India and Molecular Biophysics Unit, Indian Institute of Science, Bangalore-560012, India.
| | - Nagasuma R Chandra
- Department of Biochemistry, Indian Institute of Science, Bangalore-560012, India
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5
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Minato Y, Thiede JM, Kordus SL, McKlveen EJ, Turman BJ, Baughn AD. Mycobacterium tuberculosis folate metabolism and the mechanistic basis for para-aminosalicylic acid susceptibility and resistance. Antimicrob Agents Chemother 2015; 59:5097-106. [PMID: 26033719 PMCID: PMC4538520 DOI: 10.1128/aac.00647-15] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
para-Aminosalicylic acid (PAS) entered clinical use in 1946 as the second exclusive drug for the treatment of tuberculosis (TB). While PAS was initially a first-line TB drug, the introduction of more potent antitubercular agents relegated PAS to the second-line tier of agents used for the treatment of drug-resistant Mycobacterium tuberculosis infections. Despite the long history of PAS usage, an understanding of the molecular and biochemical mechanisms governing the susceptibility and resistance of M. tuberculosis to this drug has lagged behind that of most other TB drugs. Herein, we discuss previous studies that demonstrate PAS-mediated disruption of iron acquisition, as well as recent genetic, biochemical, and metabolomic studies that have revealed that PAS is a prodrug that ultimately corrupts one-carbon metabolism through inhibition of the formation of reduced folate species. We also discuss findings from laboratory and clinical isolates that link alterations in folate metabolism to PAS resistance. These advancements in our understanding of the basis of the susceptibility and resistance of M. tuberculosis to PAS will enable the development of novel strategies to revitalize this and other antimicrobial agents for use in the global effort to eradicate TB.
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Affiliation(s)
- Yusuke Minato
- Department of Microbiology, Center for Infectious Diseases and Microbiology Translational Research, University of Minnesota Medical School, Minneapolis, Minnesota, USA
| | - Joshua M Thiede
- Department of Microbiology, Center for Infectious Diseases and Microbiology Translational Research, University of Minnesota Medical School, Minneapolis, Minnesota, USA
| | - Shannon Lynn Kordus
- Department of Microbiology, Center for Infectious Diseases and Microbiology Translational Research, University of Minnesota Medical School, Minneapolis, Minnesota, USA
| | - Edward J McKlveen
- Department of Chemistry, Harvard University, Cambridge, Massachusetts, USA
| | - Breanna J Turman
- Department of Microbiology, Center for Infectious Diseases and Microbiology Translational Research, University of Minnesota Medical School, Minneapolis, Minnesota, USA
| | - Anthony D Baughn
- Department of Microbiology, Center for Infectious Diseases and Microbiology Translational Research, University of Minnesota Medical School, Minneapolis, Minnesota, USA
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6
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Utility of the Biosynthetic Folate Pathway for Targets in Antimicrobial Discovery. Antibiotics (Basel) 2014; 3:1-28. [PMID: 27025730 PMCID: PMC4790348 DOI: 10.3390/antibiotics3010001] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Revised: 01/08/2014] [Accepted: 01/09/2014] [Indexed: 01/07/2023] Open
Abstract
The need for new antimicrobials is great in face of a growing pool of resistant pathogenic organisms. This review will address the potential for antimicrobial therapy based on polypharmacological activities within the currently utilized bacterial biosynthetic folate pathway. The folate metabolic pathway leads to synthesis of required precursors for cellular function and contains a critical node, dihydrofolate reductase (DHFR), which is shared between prokaryotes and eukaryotes. The DHFR enzyme is currently targeted by methotrexate in anti-cancer therapies, by trimethoprim for antibacterial uses, and by pyrimethamine for anti-protozoal applications. An additional anti-folate target is dihyropteroate synthase (DHPS), which is unique to prokaryotes as they cannot acquire folate through dietary means. It has been demonstrated as a primary target for the longest standing antibiotic class, the sulfonamides, which act synergistically with DHFR inhibitors. Investigations have revealed most DHPS enzymes possess the ability to utilize sulfa drugs metabolically, producing alternate products that presumably inhibit downstream enzymes requiring the produced dihydropteroate. Recent work has established an off-target effect of sulfonamide antibiotics on a eukaryotic enzyme, sepiapterin reductase, causing alterations in neurotransmitter synthesis. Given that inhibitors of both DHFR and DHPS are designed to mimic their cognate substrate, which contain shared substructures, it is reasonable to expect such “off-target” effects. These inhibitors are also likely to interact with the enzymatic neighbors in the folate pathway that bind products of the DHFR or DHPS enzymes and/or substrates of similar substructure. Computational studies designed to assess polypharmacology reiterate these conclusions. This leads to hypotheses exploring the vast utility of multiple members of the folate pathway for modulating cellular metabolism, and includes an appealing capacity for prokaryotic-specific polypharmacology for antimicrobial applications.
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7
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Binding pocket alterations in dihydrofolate synthase confer resistance to para-aminosalicylic acid in clinical isolates of Mycobacterium tuberculosis. Antimicrob Agents Chemother 2013; 58:1479-87. [PMID: 24366731 DOI: 10.1128/aac.01775-13] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The mechanistic basis for the resistance of Mycobacterium tuberculosis to para-aminosalicylic acid (PAS), an important agent in the treatment of multidrug-resistant tuberculosis, has yet to be fully defined. As a substrate analog of the folate precursor para-aminobenzoic acid, PAS is ultimately bioactivated to hydroxy dihydrofolate, which inhibits dihydrofolate reductase and disrupts the operation of folate-dependent metabolic pathways. As a result, the mutation of dihydrofolate synthase, an enzyme needed for the bioactivation of PAS, causes PAS resistance in M. tuberculosis strain H37Rv. Here, we demonstrate that various missense mutations within the coding sequence of the dihydropteroate (H2Pte) binding pocket of dihydrofolate synthase (FolC) confer PAS resistance in laboratory isolates of M. tuberculosis and Mycobacterium bovis. From a panel of 85 multidrug-resistant M. tuberculosis clinical isolates, 5 were found to harbor mutations in the folC gene within the H2Pte binding pocket, resulting in PAS resistance. While these alterations in the H2Pte binding pocket resulted in reduced dihydrofolate synthase activity, they also abolished the bioactivation of hydroxy dihydropteroate to hydroxy dihydrofolate. Consistent with this model for abolished bioactivation, the introduction of a wild-type copy of folC fully restored PAS susceptibility in folC mutant strains. Confirmation of this novel PAS resistance mechanism will be beneficial for the development of molecular method-based diagnostics for M. tuberculosis clinical isolates and for further defining the mode of action of this important tuberculosis drug.
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Meigh L, Greenhalgh SA, Rodgers TL, Cann MJ, Roper DI, Dale N. CO₂directly modulates connexin 26 by formation of carbamate bridges between subunits. eLife 2013; 2:e01213. [PMID: 24220509 PMCID: PMC3821526 DOI: 10.7554/elife.01213] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Homeostatic regulation of the partial pressure of CO2 (PCO2) is vital for life. Sensing of pH has been proposed as a sufficient proxy for determination of PCO2 and direct CO2-sensing largely discounted. Here we show that connexin 26 (Cx26) hemichannels, causally linked to respiratory chemosensitivity, are directly modulated by CO2. A ‘carbamylation motif’, present in CO2-sensitive connexins (Cx26, Cx30, Cx32) but absent from a CO2-insensitive connexin (Cx31), comprises Lys125 and four further amino acids that orient Lys125 towards Arg104 of the adjacent subunit of the connexin hexamer. Introducing the carbamylation motif into Cx31 created a mutant hemichannel (mCx31) that was opened by increases in PCO2. Mutation of the carbamylation motif in Cx26 and mCx31 destroyed CO2 sensitivity. Course-grained computational modelling of Cx26 demonstrated that the proposed carbamate bridge between Lys125 and Arg104 biases the hemichannel to the open state. Carbamylation of Cx26 introduces a new transduction principle for physiological sensing of CO2. DOI:http://dx.doi.org/10.7554/eLife.01213.001 A number of gaseous molecules, including nitric oxide and carbon monoxide, play important roles in many cellular processes by acting as signalling molecules. Surprisingly, however, it has long been assumed that carbon dioxide – a gaseous molecule that is produced during cellular metabolism – is not a signalling molecule. Controlling the concentration of carbon dioxide (CO2) in a biological system is essential to sustain life, and it was thought that the body used pH – which is the concentration of hydrogen ions – as a proxy for the level of CO2. The concentration of CO2 is related to pH because CO2 reacts with water to form carbonic acid, which quickly breaks down to form hydrogen ions and bicarbonate ions. This close relationship has led many researchers to equate pH-sensing with CO2-sensing, and to suggest that a physiological receptor for CO2 does not exist. Recent research into structures called connexin hemichannels has challenged this view. Researchers found that when pH levels were held constant, increasing the level of CO2 caused the structures to open up, suggesting that CO2 could be directly detected by the hemichannels. Each hemichannel contains six connexin subunits, but the details of how the CO2 molecules interact with the individual connexin subunits to open up the hemichannels remained mysterious. Now Meigh et al. show that CO2 molecules bind to a specific amino acid (lysine) at a particular place (residue 125) in one of the connexin subunits to form a carbamate group. This group then interacts with the amino acid (arginine) at residue 104 in a neighbouring connexin subunit to form a carbamate bridge between the two subunits. This leads to structural changes that cause the gap junction hemichannels to open and release signals that can activate other cells. Since connexin hemichannels are found throughout the human body, these results suggest that CO2 might act as a signalling molecule in processes as diverse as the control of blood flow, breathing, hearing and reproduction. DOI:http://dx.doi.org/10.7554/eLife.01213.002
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Affiliation(s)
- Louise Meigh
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
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9
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Zheng J, Rubin EJ, Bifani P, Mathys V, Lim V, Au M, Jang J, Nam J, Dick T, Walker JR, Pethe K, Camacho LR. para-Aminosalicylic acid is a prodrug targeting dihydrofolate reductase in Mycobacterium tuberculosis. J Biol Chem 2013; 288:23447-56. [PMID: 23779105 DOI: 10.1074/jbc.m113.475798] [Citation(s) in RCA: 129] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
para-Aminosalicylic acid (PAS) is one of the antimycobacterial drugs currently used for multidrug-resistant tuberculosis. Although it has been in clinical use for over 60 years, its mechanism(s) of action remains elusive. Here we report that PAS is a prodrug targeting dihydrofolate reductase (DHFR) through an unusual and novel mechanism of action. We provide evidences that PAS is incorporated into the folate pathway by dihydropteroate synthase (DHPS) and dihydrofolate synthase (DHFS) to generate a hydroxyl dihydrofolate antimetabolite, which in turn inhibits DHFR enzymatic activity. Interestingly, PAS is recognized by DHPS as efficiently as its natural substrate para-amino benzoic acid. Chemical inhibition of DHPS or mutation in DHFS prevents the formation of the antimetabolite, thereby conferring resistance to PAS. In addition, we identified a bifunctional enzyme (riboflavin biosynthesis protein (RibD)), a putative functional analog of DHFR in a knock-out strain. This finding is further supported by the identification of PAS-resistant clinical isolates encoding a RibD overexpression mutation displaying cross-resistance to genuine DHFR inhibitors. Our findings reveal that a metabolite of PAS inhibits DHFR in the folate pathway. RibD was shown to act as a functional analog of DHFR, and as for DHFS, both were shown to be associated in PAS resistance in laboratory strains and clinical isolates.
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Affiliation(s)
- Jun Zheng
- Novartis Institute for Tropical Diseases, Singapore 138670.
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10
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Danchin A, Binder PM, Noria S. Antifragility and Tinkering in Biology (and in Business) Flexibility Provides an Efficient Epigenetic Way to Manage Risk. Genes (Basel) 2011; 2:998-1016. [PMID: 24710302 PMCID: PMC3927596 DOI: 10.3390/genes2040998] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Revised: 10/25/2011] [Accepted: 11/16/2011] [Indexed: 12/25/2022] Open
Abstract
The notion of antifragility, an attribute of systems that makes them thrive under variable conditions, has recently been proposed by Nassim Taleb in a business context. This idea requires the ability of such systems to 'tinker', i.e., to creatively respond to changes in their environment. A fairly obvious example of this is natural selection-driven evolution. In this ubiquitous process, an original entity, challenged by an ever-changing environment, creates variants that evolve into novel entities. Analyzing functions that are essential during stationary-state life yield examples of entities that may be antifragile. One such example is proteins with flexible regions that can undergo functional alteration of their side residues or backbone and thus implement the tinkering that leads to antifragility. This in-built property of the cell chassis must be taken into account when considering construction of cell factories driven by engineering principles.
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Affiliation(s)
- Antoine Danchin
- AMAbiotics SAS, CEA/Genoscope, 2 rue Gaston Crémieux, 91057 Evry Cedex, France.
| | - Philippe M Binder
- Natural Sciences Division, University of Hawaii, Hilo, HI 96720-4091, USA.
| | - Stanislas Noria
- Fondation Fourmentin-Guilbert, 2 avenue du Pavé Neuf, 93160 Noisy-le-Grand, France.
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11
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Li Y, Yu X, Ho J, Fushman D, Allewell NM, Tuchman M, Shi D. Reversible post-translational carboxylation modulates the enzymatic activity of N-acetyl-L-ornithine transcarbamylase. Biochemistry 2010; 49:6887-95. [PMID: 20695527 DOI: 10.1021/bi1007386] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
N-Acetyl-l-ornithine transcarbamylase (AOTCase), rather than ornithine transcarbamylase (OTCase), is the essential carbamylase enzyme in the arginine biosynthesis of several plant and human pathogens. The specificity of this unique enzyme provides a potential target for controlling the spread of these pathogens. Recently, several crystal structures of AOTCase from Xanthomonas campestris (xc) have been determined. In these structures, an unexplained electron density at the tip of the Lys302 side chain was observed. Using (13)C NMR spectroscopy, we show herein that Lys302 is post-translationally carboxylated. The structure of wild-type AOTCase in a complex with the bisubstrate analogue N(delta)-(phosphonoacetyl)-N(alpha)-acetyl-l-ornithine (PALAO) indicates that the carboxyl group on Lys302 forms a strong hydrogen bonding network with surrounding active site residues, Lys252, Ser253, His293, and Glu92 from the adjacent subunit either directly or via a water molecule. Furthermore, the carboxyl group is involved in binding N-acetyl-l-ornithine via a water molecule. Activity assays with the wild-type enzyme and several mutants demonstrate that the post-translational modification of lysine 302 has an important role in catalysis.
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Affiliation(s)
- Yongdong Li
- Research Center for Genetic Medicine and Department of Integrative Systems Biology, Children's National Medical Center, The George Washington University, Washington, DC 20010, USA
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12
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Wang P, Wang Q, Yang Y, Coward JK, Nzila A, Sims PF, Hyde JE. Characterisation of the bifunctional dihydrofolate synthase-folylpolyglutamate synthase from Plasmodium falciparum; a potential novel target for antimalarial antifolate inhibition. Mol Biochem Parasitol 2010; 172:41-51. [PMID: 20350571 PMCID: PMC2877875 DOI: 10.1016/j.molbiopara.2010.03.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2010] [Revised: 03/15/2010] [Accepted: 03/16/2010] [Indexed: 11/20/2022]
Abstract
Unusually for a eukaryote, the malaria parasite Plasmodium falciparum expresses dihydrofolate synthase (DHFS) and folylpolyglutamate synthase (FPGS) as a single bifunctional protein. The two activities contribute to the essential pathway of folate biosynthesis and modification. The DHFS activity of recombinant PfDHFS–FPGS exhibited non-standard kinetics at high co-substrate (glutamate and ATP) concentrations, being partially inhibited by increasing concentrations of its principal substrate, dihydropteroate (DHP). Binding of DHP to the catalytic and inhibitory sites exhibited dissociation constants of 0.50 μM and 1.25 μM, respectively. DHFS activity measured under lower co-substrate concentrations, where data fitted the Michaelis–Menten equation, yielded apparent Km values of 0.88 μM for DHP, 22.8 μM for ATP and 5.97 μM for glutamate. Of the substrates tested in FPGS assays, only tetrahydrofolate (THF) was efficiently converted to polyglutamylated forms, exhibiting standard kinetics with an apparent Km of 0.96 μM; dihydrofolate, folate and the folate analogue methotrexate (MTX) were negligibly processed, emphasising the importance of the oxidation state of the pterin moiety. Moreover, MTX inhibited neither DHFS nor FPGS, even at high concentrations. Conversely, two phosphinate analogues of 7,8-dihydrofolate that mimic tetrahedral intermediates formed during DHFS- and FPGS-catalysed glutamylation were powerfully inhibitory. The Ki value of an aryl phosphinate analogue against DHFS was 0.14 μM and for an alkyl phosphinate against FPGS 0.091 μM, with each inhibitor showing a high degree of specificity. This, combined with the absence of DHFS activity in humans, suggests PfDHFS–FPGS might represent a potential new drug target in the previously validated folate pathway of P. falciparum.
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Affiliation(s)
- Ping Wang
- Manchester Interdisciplinary Biocentre, Faculty of Life Sciences, University of Manchester, 131 Princess Street, Manchester M1 7DN, UK
| | - Qi Wang
- Manchester Interdisciplinary Biocentre, Faculty of Life Sciences, University of Manchester, 131 Princess Street, Manchester M1 7DN, UK
| | - Yonghong Yang
- Department of Medicinal Chemistry, University of Michigan, 930 N. University, Ann Arbor, MI 48109-1055, USA
- Department of Chemistry, University of Michigan, 930 N. University, Ann Arbor, MI 48109-1055, USA
| | - James K. Coward
- Department of Medicinal Chemistry, University of Michigan, 930 N. University, Ann Arbor, MI 48109-1055, USA
- Department of Chemistry, University of Michigan, 930 N. University, Ann Arbor, MI 48109-1055, USA
| | - Alexis Nzila
- KEMRI, Wellcome Trust Collaborative Research Programme, Kilifi 80108, Kenya
| | - Paul F.G. Sims
- Manchester Interdisciplinary Biocentre, Faculty of Life Sciences, University of Manchester, 131 Princess Street, Manchester M1 7DN, UK
| | - John E. Hyde
- Manchester Interdisciplinary Biocentre, Faculty of Life Sciences, University of Manchester, 131 Princess Street, Manchester M1 7DN, UK
- Corresponding author at: University of Manchester, Faculty of Life Sciences, Manchester Interdisciplinary Biocentre, 131 Princess St, Manchester M1 7DN, UK. Tel.: +44 161 306 4185; fax: +44 161 306 5201.
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