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Murch AL, Skipp PJ, Roach PL, Oyston PCF. Whole genome transcriptomics reveals global effects including up-regulation of Francisella pathogenicity island gene expression during active stringent response in the highly virulent Francisella tularensis subsp. tularensis SCHU S4. Microbiology (Reading) 2017; 163:1664-1679. [PMID: 29034854 PMCID: PMC5845702 DOI: 10.1099/mic.0.000550] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
During conditions of nutrient limitation bacteria undergo a series of global gene expression changes to survive conditions of amino acid and fatty acid starvation. Rapid reallocation of cellular resources is brought about by gene expression changes coordinated by the signalling nucleotides' guanosine tetraphosphate or pentaphosphate, collectively termed (p)ppGpp and is known as the stringent response. The stringent response has been implicated in bacterial virulence, with elevated (p)ppGpp levels being associated with increased virulence gene expression. This has been observed in the highly pathogenic Francisella tularensis sub spp. tularensis SCHU S4, the causative agent of tularaemia. Here, we aimed to artificially induce the stringent response by culturing F. tularensis in the presence of the amino acid analogue l-serine hydroxamate. Serine hydroxamate competitively inhibits tRNAser aminoacylation, causing an accumulation of uncharged tRNA. The uncharged tRNA enters the A site on the translating bacterial ribosome and causes ribosome stalling, in turn stimulating the production of (p)ppGpp and activation of the stringent response. Using the essential virulence gene iglC, which is encoded on the Francisella pathogenicity island (FPI) as a marker of active stringent response, we optimized the culture conditions required for the investigation of virulence gene expression under conditions of nutrient limitation. We subsequently used whole genome RNA-seq to show how F. tularensis alters gene expression on a global scale during active stringent response. Key findings included up-regulation of genes involved in virulence, stress responses and metabolism, and down-regulation of genes involved in metabolite transport and cell division. F. tularensis is a highly virulent intracellular pathogen capable of causing debilitating or fatal disease at extremely low infectious doses. However, virulence mechanisms are still poorly understood. The stringent response is widely recognized as a diverse and complex bacterial stress response implicated in virulence. This work describes the global gene expression profile of F. tularensis SCHU S4 under active stringent response for the first time. Herein we provide evidence for an association of active stringent response with FPI virulence gene expression. Our results further the understanding of the molecular basis of virulence and regulation thereof in F. tularensis. These results also support research into genes involved in (p)ppGpp production and polyphosphate biosynthesis and their applicability as targets for novel antimicrobials.
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Affiliation(s)
- Amber L Murch
- CBR Division, Defence Science and Technology Laboratory, Salisbury, UK
| | - Paul J Skipp
- School of Chemistry, University of Southampton, Southampton, UK
| | - Peter L Roach
- School of Chemistry, University of Southampton, Southampton, UK
| | - Petra C F Oyston
- CBR Division, Defence Science and Technology Laboratory, Salisbury, UK
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Dinis P, Wieckowski BM, Roach PL. Metallocofactor assembly for [FeFe]-hydrogenases. Curr Opin Struct Biol 2016; 41:90-97. [PMID: 27344601 DOI: 10.1016/j.sbi.2016.06.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2016] [Revised: 06/05/2016] [Accepted: 06/06/2016] [Indexed: 11/27/2022]
Abstract
Hydrogenases are a potential source of environmentally benign bioenergy, using complex cofactors to catalyze the reversible reduction of protons to form hydrogen. The most active subclass, the [FeFe]-hydrogenases, is dependent on a metallocofactor, the H cluster, that consists of a two iron subcluster ([2Fe]H) bridging to a classical cubane cluster ([4Fe-4S]H). The ligands coordinating to the diiron subcluster include an azadithiolate, three carbon monoxides, and two cyanides. To assemble this complex cofactor, three maturase enzymes, HydG, HydE and HydF are required. The biosynthesis of the diatomic ligands proceeds by an unusual fragmentation mechanism, and structural studies in combination with spectroscopic analysis have started to provide insights into the HydG mediated assembly of a [2Fe]H subcluster precursor.
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Affiliation(s)
- Pedro Dinis
- Chemistry and the Institute for Life Sciences, University of Southampton, Highfield Campus, Southampton SO17 1BJ, UK
| | - Beata M Wieckowski
- Chemistry and the Institute for Life Sciences, University of Southampton, Highfield Campus, Southampton SO17 1BJ, UK
| | - Peter L Roach
- Chemistry and the Institute for Life Sciences, University of Southampton, Highfield Campus, Southampton SO17 1BJ, UK.
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McKelvie JC, Richards MI, Harmer JE, Milne TS, Roach PL, Oyston PCF. Inhibition of Yersinia pestis DNA adenine methyltransferase in vitro by a stibonic acid compound: identification of a potential novel class of antimicrobial agents. Br J Pharmacol 2014; 168:172-88. [PMID: 22889062 DOI: 10.1111/j.1476-5381.2012.02134.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Revised: 07/04/2012] [Accepted: 07/14/2012] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND AND PURPOSE Multiple antibiotic resistant strains of plague are emerging, driving a need for the development of novel antibiotics effective against Yersinia pestis. DNA adenine methylation regulates numerous fundamental processes in bacteria and alteration of DNA adenine methlytransferase (Dam) expression is attenuating for several pathogens, including Y. pestis. The lack of a functionally similar enzyme in humans makes Dam a suitable target for development of novel therapeutics for plague. EXPERIMENTAL APPROACH Compounds were evaluated for their ability to inhibit Dam activity in a high-throughput screening assay. DNA was isolated from Yersinia grown in the presence of lead compounds and restricted to determine the effect of inhibitors on DNA methylation. Transcriptional analysis was undertaken to determine the effect of an active inhibitor on virulence-associated phenotypes. KEY RESULTS We have identified a series of aryl stibonic acids which inhibit Dam in vitro. The most active, 4-stibonobenzenesulfonic acid, exhibited a competitive mode of inhibition with respect to DNA and a K(i) of 6.46 nM. One compound was found to inhibit DNA methylation in cultured Y. pestis. The effects of this inhibition on the physiology of the cell were widespread, and included altered expression of known virulence traits, including iron acquisition and Type III secretion. CONCLUSIONS AND IMPLICATIONS We have identified a novel class of potent Dam inhibitors. Treatment of bacterial cell cultures with these inhibitors resulted in a decrease in DNA methylation. Expression of virulence factors was affected, suggesting these inhibitors may attenuate bacterial infectivity and function as antibiotics.
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Affiliation(s)
- J C McKelvie
- School of Chemistry, University of Southampton, UK
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Driesener RC, Duffus BR, Shepard EM, Bruzas IR, Duschene KS, Coleman NJR, Marrison APG, Salvadori E, Kay CWM, Peters JW, Broderick JB, Roach PL. Biochemical and kinetic characterization of radical S-adenosyl-L-methionine enzyme HydG. Biochemistry 2013; 52:8696-707. [PMID: 24206022 DOI: 10.1021/bi401143s] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The radical S-adenosyl-L-methionine (AdoMet) enzyme HydG is one of three maturase enzymes involved in [FeFe]-hydrogenase H-cluster assembly. It catalyzes L-tyrosine cleavage to yield the H-cluster cyanide and carbon monoxide ligands as well as p-cresol. Clostridium acetobutylicum HydG contains the conserved CX3CX2C motif coordinating the AdoMet binding [4Fe-4S] cluster and a C-terminal CX2CX22C motif proposed to coordinate a second [4Fe-4S] cluster. To improve our understanding of the roles of each of these iron-sulfur clusters in catalysis, we have generated HydG variants lacking either the N- or C-terminal cluster and examined these using spectroscopic and kinetic methods. We have used iron analyses, UV-visible spectroscopy, and electron paramagnetic resonance (EPR) spectroscopy of an N-terminal C96/100/103A triple HydG mutant that cannot coordinate the radical AdoMet cluster to unambiguously show that the C-terminal cysteine motif coordinates an auxiliary [4Fe-4S] cluster. Spectroscopic comparison with a C-terminally truncated HydG (ΔCTD) harboring only the N-terminal cluster demonstrates that both clusters have similar UV-visible and EPR spectral properties, but that AdoMet binding and cleavage occur only at the N-terminal radical AdoMet cluster. To elucidate which steps in the catalytic cycle of HydG require the auxiliary [4Fe-4S] cluster, we compared the Michaelis-Menten constants for AdoMet and L-tyrosine for reconstituted wild-type, C386S, and ΔCTD HydG and demonstrate that these C-terminal modifications do not affect the affinity for AdoMet but that the affinity for L-tyrosine is drastically reduced compared to that of wild-type HydG. Further detailed kinetic characterization of these HydG mutants demonstrates that the C-terminal cluster and residues are not essential for L-tyrosine cleavage to p-cresol but are necessary for conversion of a tyrosine-derived intermediate to cyanide and CO.
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Affiliation(s)
- Rebecca C Driesener
- Chemistry, Faculty of Natural and Engineering Sciences, University of Southampton , Highfield SO17 1BJ, U.K
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Challand MR, Salvadori E, Driesener RC, Kay CWM, Roach PL, Spencer J. Cysteine methylation controls radical generation in the Cfr radical AdoMet rRNA methyltransferase. PLoS One 2013; 8:e67979. [PMID: 23861844 PMCID: PMC3702613 DOI: 10.1371/journal.pone.0067979] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 05/23/2013] [Indexed: 11/18/2022] Open
Abstract
The 'radical S-adenosyl-L-methionine (AdoMet)' enzyme Cfr methylates adenosine 2503 of the 23S rRNA in the peptidyltransferase centre (P-site) of the bacterial ribosome. This modification protects host bacteria, notably methicillin-resistant Staphylococcus aureus (MRSA), from numerous antibiotics, including agents (e.g. linezolid, retapamulin) that were developed to treat such organisms. Cfr contains a single [4Fe-4S] cluster that binds two separate molecules of AdoMet during the reaction cycle. These are used sequentially to first methylate a cysteine residue, Cys338; and subsequently generate an oxidative radical intermediate that facilitates methyl transfer to the unreactive C8 (and/or C2) carbon centres of adenosine 2503. How the Cfr active site, with its single [4Fe-4S] cluster, catalyses these two distinct activities that each utilise AdoMet as a substrate remains to be established. Here, we use absorbance and electron paramagnetic resonance (EPR) spectroscopy to investigate the interactions of AdoMet with the [4Fe-4S] clusters of wild-type Cfr and a Cys338 Ala mutant, which is unable to accept a methyl group. Cfr binds AdoMet with high (∼ 10 µM) affinity notwithstanding the absence of the RNA cosubstrate. In wild-type Cfr, where Cys338 is methylated, AdoMet binding leads to rapid oxidation of the [4Fe-4S] cluster and production of 5'-deoxyadenosine (DOA). In contrast, while Cys338 Ala Cfr binds AdoMet with equivalent affinity, oxidation of the [4Fe-4S] cluster is not observed. Our results indicate that the presence of a methyl group on Cfr Cys338 is a key determinant of the activity of the enzyme towards AdoMet, thus enabling a single active site to support two distinct modes of AdoMet cleavage.
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Affiliation(s)
- Martin R. Challand
- School of Cellular and Molecular Medicine, University of Bristol Medical Sciences Building, Bristol, United Kingdom
| | - Enrico Salvadori
- Institute of Structural and Molecular Biology, University College London, London, United Kingdom
- London Centre for Nanotechnology, University College London, London, United Kingdom
| | | | - Christopher W. M. Kay
- Institute of Structural and Molecular Biology, University College London, London, United Kingdom
- London Centre for Nanotechnology, University College London, London, United Kingdom
- * E-mail: (CWMK); (PLR); (JS)
| | - Peter L. Roach
- Chemistry, University of Southampton, Highfield, Southampton, United Kingdom
- Institute for Life Sciences, University of Southampton, Highfield, Southampton, United Kingdom
- * E-mail: (CWMK); (PLR); (JS)
| | - James Spencer
- School of Cellular and Molecular Medicine, University of Bristol Medical Sciences Building, Bristol, United Kingdom
- * E-mail: (CWMK); (PLR); (JS)
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Hobley G, McKelvie JC, Harmer JE, Howe J, Oyston PC, Roach PL. Development of rationally designed DNA N6 adenine methyltransferase inhibitors. Bioorg Med Chem Lett 2012; 22:3079-82. [DOI: 10.1016/j.bmcl.2012.03.072] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2011] [Revised: 03/16/2012] [Accepted: 03/19/2012] [Indexed: 01/12/2023]
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Hakim MMA, Lombardini M, Sun K, Giustiniano F, Roach PL, Davies DE, Howarth PH, de Planque MRR, Morgan H, Ashburn P. Thin film polycrystalline silicon nanowire biosensors. Nano Lett 2012; 12:1868-1872. [PMID: 22432636 DOI: 10.1021/nl2042276] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Polysilicon nanowire biosensors have been fabricated using a top-down process and were used to determine the binding constant of two inflammatory biomarkers. A very low cost nanofabrication process was developed, based on simple and mature photolithography, thin film technology, and plasma etching, enabling an easy route to mass manufacture. Antibody-functionalized nanowire sensors were used to detect the proteins interleukin-8 (IL-8) and tumor necrosis factor-alpha (TNF-α) over a wide range of concentrations, demonstrating excellent sensitivity and selectivity, exemplified by a detection sensitivity of 10 fM in the presence of a 100,000-fold excess of a nontarget protein. Nanowire titration curves gave antibody-antigen dissociation constants in good agreement with low-salt enzyme-linked immunosorbent assays (ELISAs). This fabrication process produces high-quality nanowires that are suitable for low-cost mass production, providing a realistic route to the realization of disposable nanoelectronic point-of-care (PoC) devices.
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Affiliation(s)
- Mohammad M A Hakim
- School of Electronics & Computer Science, University of Southampton, Southampton, SO17 1BJ, UK.
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Hiscox MJ, Driesener RC, Roach PL. Enzyme catalyzed formation of radicals from S-adenosylmethionine and inhibition of enzyme activity by the cleavage products. Biochim Biophys Acta 2012; 1824:1165-77. [PMID: 22504666 DOI: 10.1016/j.bbapap.2012.03.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2011] [Revised: 03/06/2012] [Accepted: 03/27/2012] [Indexed: 01/06/2023]
Abstract
A large superfamily of enzymes have been identified that make use of radical intermediates derived by reductive cleavage of S-adenosylmethionine. The primary nature of the radical intermediates makes them highly reactive and potent oxidants. They are used to initiate biotransformations by hydrogen atom abstraction, a process that allows a particularly diverse range of substrates to be functionalized, including substrates with relatively inert chemical structures. In the first part of this review, we discuss the evidence supporting the mechanism of radical formation from S-adenosylmethionine. In the second part of the review, we examine the potential of reaction products arising from S-adenosylmethionine to cause product inhibition. The effects of this product inhibition on kinetic studies of 'radical S-adenosylmethionine' enzymes are discussed and strategies to overcome these issues are reviewed. This article is part of a Special Issue entitled: Radical SAM enzymes and Radical Enzymology.
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Affiliation(s)
- Martyn J Hiscox
- School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK
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Affiliation(s)
- Martin R Challand
- School of Cellular and Molecular Medicine, Medical Sciences Building, University of Bristol, University Walk, Bristol BS81TD, USA
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10
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Broder GR, Ranasinghe RT, Neylon C, Morgan H, Roach PL. Kinetics and Thermodynamics of Biotinylated Oligonucleotide Probe Binding to Particle-Immobilized Avidin and Implications for Multiplexing Applications. Anal Chem 2011; 83:2005-11. [DOI: 10.1021/ac102762q] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | | | - Cameron Neylon
- STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot OX11 0QX, U.K
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11
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Roach PL. Radicals from S-adenosylmethionine and their application to biosynthesis. Curr Opin Chem Biol 2010; 15:267-75. [PMID: 21159543 DOI: 10.1016/j.cbpa.2010.11.015] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2010] [Revised: 11/04/2010] [Accepted: 11/16/2010] [Indexed: 01/15/2023]
Abstract
The radical SAM superfamily of enzymes catalyzes a broad spectrum of biotransformations by employing a common obligate intermediate, the 5'-deoxyadenosyl radical (DOA). Radical formation occurs via the reductive cleavage of S-adenosylmethionine (SAM or AdoMet). The resultant highly reactive primary radical is a potent oxidant that enables the functionalization of relatively inert substrates, including unactivated C-H bonds. The reactions initiated by the DOA are breathtaking in their efficiency, elegance and in many cases, the complexity of the biotransformation achieved. This review describes the common features shared by enzymes that generate the DOA and the intriguing variations or modifications that have recently been reported. The review also highlights selected examples of the diverse biotransformations that ensue.
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Affiliation(s)
- Peter L Roach
- School of Chemistry, University of Southampton, Southampton SO17 1BJ, UK.
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Booth MP, Challand MR, Emery DC, Roach PL, Spencer J. High-level expression and reconstitution of active Cfr, a radical-SAM rRNA methyltransferase that confers resistance to ribosome-acting antibiotics. Protein Expr Purif 2010; 74:204-10. [DOI: 10.1016/j.pep.2010.07.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2010] [Revised: 07/25/2010] [Accepted: 07/26/2010] [Indexed: 11/25/2022]
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Shepard EM, Duffus BR, George SJ, McGlynn SE, Challand MR, Swanson KD, Roach PL, Cramer SP, Peters JW, Broderick JB. [FeFe]-Hydrogenase Maturation: HydG-Catalyzed Synthesis of Carbon Monoxide. J Am Chem Soc 2010; 132:9247-9. [DOI: 10.1021/ja1012273] [Citation(s) in RCA: 119] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Eric M. Shepard
- Department of Chemistry & Biochemistry and Astrobiology Biogeocatalysis Research Center, Montana State University, Bozeman, Montana 59717, Department of Applied Science, University of California—Davis, Davis, California 95616, Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and School of Chemistry, University of Southampton, Southampton SO17 1BJ, U.K
| | - Benjamin R. Duffus
- Department of Chemistry & Biochemistry and Astrobiology Biogeocatalysis Research Center, Montana State University, Bozeman, Montana 59717, Department of Applied Science, University of California—Davis, Davis, California 95616, Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and School of Chemistry, University of Southampton, Southampton SO17 1BJ, U.K
| | - Simon J. George
- Department of Chemistry & Biochemistry and Astrobiology Biogeocatalysis Research Center, Montana State University, Bozeman, Montana 59717, Department of Applied Science, University of California—Davis, Davis, California 95616, Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and School of Chemistry, University of Southampton, Southampton SO17 1BJ, U.K
| | - Shawn E. McGlynn
- Department of Chemistry & Biochemistry and Astrobiology Biogeocatalysis Research Center, Montana State University, Bozeman, Montana 59717, Department of Applied Science, University of California—Davis, Davis, California 95616, Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and School of Chemistry, University of Southampton, Southampton SO17 1BJ, U.K
| | - Martin R. Challand
- Department of Chemistry & Biochemistry and Astrobiology Biogeocatalysis Research Center, Montana State University, Bozeman, Montana 59717, Department of Applied Science, University of California—Davis, Davis, California 95616, Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and School of Chemistry, University of Southampton, Southampton SO17 1BJ, U.K
| | - Kevin D. Swanson
- Department of Chemistry & Biochemistry and Astrobiology Biogeocatalysis Research Center, Montana State University, Bozeman, Montana 59717, Department of Applied Science, University of California—Davis, Davis, California 95616, Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and School of Chemistry, University of Southampton, Southampton SO17 1BJ, U.K
| | - Peter L. Roach
- Department of Chemistry & Biochemistry and Astrobiology Biogeocatalysis Research Center, Montana State University, Bozeman, Montana 59717, Department of Applied Science, University of California—Davis, Davis, California 95616, Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and School of Chemistry, University of Southampton, Southampton SO17 1BJ, U.K
| | - Stephen P. Cramer
- Department of Chemistry & Biochemistry and Astrobiology Biogeocatalysis Research Center, Montana State University, Bozeman, Montana 59717, Department of Applied Science, University of California—Davis, Davis, California 95616, Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and School of Chemistry, University of Southampton, Southampton SO17 1BJ, U.K
| | - John W. Peters
- Department of Chemistry & Biochemistry and Astrobiology Biogeocatalysis Research Center, Montana State University, Bozeman, Montana 59717, Department of Applied Science, University of California—Davis, Davis, California 95616, Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and School of Chemistry, University of Southampton, Southampton SO17 1BJ, U.K
| | - Joan B. Broderick
- Department of Chemistry & Biochemistry and Astrobiology Biogeocatalysis Research Center, Montana State University, Bozeman, Montana 59717, Department of Applied Science, University of California—Davis, Davis, California 95616, Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, and School of Chemistry, University of Southampton, Southampton SO17 1BJ, U.K
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Driesener RC, Challand MR, McGlynn SE, Shepard EM, Boyd ES, Broderick JB, Peters JW, Roach PL. [FeFe]-hydrogenase cyanide ligands derived from S-adenosylmethionine-dependent cleavage of tyrosine. Angew Chem Int Ed Engl 2010; 49:1687-90. [PMID: 20108298 DOI: 10.1002/anie.200907047] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Abstract
A real-time assay for CpG-specific cytosine-C5 methyltransferase activity has been developed. The assay applies a break light oligonucleotide in which the methylation of an unmethylated 5′-CG-3′ site is enzymatically coupled to the development of a fluorescent signal. This sensitive assay can measure rates of DNA methylation down to 0.34 ± 0.06 fmol/s. The assay is reproducible, with a coefficient of variation over six independent measurements of 4.5%. Product concentration was accurately measured from fluorescence signals using a linear calibration curve, which achieved a goodness of fit (R2) above 0.98. The oligonucleotide substrate contains three C5-methylated cytosine residues and one unmethylated 5′-CG-3′ site. Methylation yields an oligonucleotide containing the optimal substrate for the restriction enzyme GlaI. Cleavage of the fully methylated oligonucleotide leads to separation of fluorophore from quencher, giving a proportional increase in fluorescence. This method has been used to assay activity of DNMT1, the principle maintenance methyltransferase in human cells, and for the kinetic characterization of the bacterial cytosine-C5 methyltransferase M.SssI. The assay has been shown to be suitable for the real-time monitoring of DNMT1 activity in a high-throughput format, with low background signal and the ability to obtain linear rates of methylation over long periods, making this a promising method of high-throughput screening for inhibitors.
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Affiliation(s)
- Robert J Wood
- School of Chemistry, University of Southampton, Southampton, Hampshire, SO17 1BJ, UK
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Challand MR, Martins FT, Roach PL. Catalytic activity of the anaerobic tyrosine lyase required for thiamine biosynthesis in Escherichia coli. J Biol Chem 2009; 285:5240-8. [PMID: 19923213 DOI: 10.1074/jbc.m109.056606] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Thiazole synthase in Escherichia coli is an alphabeta heterodimer of ThiG and ThiH. ThiH is a tyrosine lyase that cleaves the C alpha-C beta bond of tyrosine, generating p-cresol as a by-product, to form dehydroglycine. This reactive intermediate acts as one of three substrates for the thiazole cyclization reaction catalyzed by ThiG. ThiH is a radical S-adenosylmethionine (AdoMet) enzyme that utilizes a [4Fe-4S](+) cluster to reductively cleave AdoMet, forming methionine and a 5'-deoxyadenosyl radical. Analysis of the time-dependent formation of the reaction products 5'-deoxyadenosine (DOA) and p-cresol has demonstrated catalytic behavior of the tyrosine lyase. The kinetics of product formation showed a pre-steady state burst phase, and the involvement of DOA in product inhibition was identified by the addition of 5'-methylthioadenosine/S-adenosylhomocysteine nucleosidase to activity assays. This hydrolyzed the DOA and changed the rate-determining step but, in addition, substantially increased the uncoupled turnover of AdoMet. Addition of glyoxylate and ammonium inhibited the tyrosine cleavage reaction, but the reductive cleavage of AdoMet continued in an uncoupled manner. Tyrosine analogues were incubated with ThiGH, which showed a strong preference for phenolic substrates. 4-Hydroxyphenylpropionic acid analogues allowed uncoupled AdoMet cleavage but did not result in further reaction (C alpha-C beta bond cleavage). The results of the substrate analogue studies and the product inhibition can be explained by a mechanistic hypothesis involving two reaction pathways, a product-forming pathway and a futile cycle.
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Affiliation(s)
- Martin R Challand
- School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, United Kingdom
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17
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Broder GR, Ranasinghe RT, She JK, Banu S, Birtwell SW, Cavalli G, Galitonov GS, Holmes D, Martins HFP, Macdonald KF, Neylon C, Zheludev N, Roach PL, Morgan H. Diffractive micro bar codes for encoding of biomolecules in multiplexed assays. Anal Chem 2008; 80:1902-9. [PMID: 18271565 DOI: 10.1021/ac7018574] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Microparticles incorporating micrometer-sized diffractive bar codes have been modified with oligonucleotides and immunoglobulin Gs to enable DNA hybridization and immunoassays. The bar codes are manufactured using photolithography of a chemically functional commercial epoxy photoresist (SU-8). When attached by suitable linkers, immobilized probe molecules exhibit high affinity for analytes and fast reaction kinetics, allowing detection of single nucleotide differences in DNA sequences and multiplexed immunoassays in <45 min. Analysis of raw data from assays carried out on the diffractive microparticles indicates that the reproducibility and sensitivity approach those of commercial encoding platforms. Micrometer-sized particles, imprinted with several superimposed diffraction gratings, can encode many million unique codes. The high encoding capacity of this technology along with the applicability of the manufactured bar codes to multiplexed assays will allow accurate measurement of a wide variety of molecular interactions, leading to new opportunities in diverse areas of biotechnology such as genomics, proteomics, high-throughput screening, and medical diagnostics.
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Affiliation(s)
- Graham R Broder
- School of Chemistry, School of Electronics and Computer Science, Optoelectronics Research Centre, and School of Physics and Astronomy, University of Southampton, Highfield, Southampton, SO17 1BJ, UK
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18
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Kriek M, Martins F, Challand MR, Croft A, Roach PL. Thiamine biosynthesis in Escherichia coli: identification of the intermediate and by-product derived from tyrosine. Angew Chem Int Ed Engl 2008; 46:9223-6. [PMID: 17969213 DOI: 10.1002/anie.200702554] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Marco Kriek
- School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK
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19
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Wood RJ, Maynard-Smith MD, Robinson VL, Oyston PC, Titball RW, Roach PL. Kinetic analysis of Yersinia pestis DNA adenine methyltransferase activity using a hemimethylated molecular break light oligonucleotide. PLoS One 2007; 2:e801. [PMID: 17726531 PMCID: PMC1949145 DOI: 10.1371/journal.pone.0000801] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2007] [Accepted: 08/05/2007] [Indexed: 11/19/2022] Open
Abstract
Background DNA adenine methylation plays an important role in several critical bacterial processes including mismatch repair, the timing of DNA replication and the transcriptional control of gene expression. The dependence of bacterial virulence on DNA adenine methyltransferase (Dam) has led to the proposal that selective Dam inhibitors might function as broad spectrum antibiotics. Methodology/Principal Findings Herein we report the expression and purification of Yersinia pestis Dam and the development of a continuous fluorescence based assay for DNA adenine methyltransferase activity that is suitable for determining the kinetic parameters of the enzyme and for high throughput screening against potential Dam inhibitors. The assay utilised a hemimethylated break light oligonucleotide substrate containing a GATC methylation site. When this substrate was fully methylated by Dam, it became a substrate for the restriction enzyme DpnI, resulting in separation of fluorophore (fluorescein) and quencher (dabcyl) and therefore an increase in fluorescence. The assays were monitored in real time using a fluorescence microplate reader in 96 well format and were used for the kinetic characterisation of Yersinia pestis Dam, its substrates and the known Dam inhibitor, S-adenosylhomocysteine. The assay has been validated for high throughput screening, giving a Z-factor of 0.71±0.07 indicating that it is a sensitive assay for the identification of inhibitors. Conclusions/Significance The assay is therefore suitable for high throughput screening for inhibitors of DNA adenine methyltransferases and the kinetic characterisation of the inhibition.
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Affiliation(s)
- Robert J. Wood
- School of Chemistry, University of Southampton, Southampton, United Kingdom
- * To whom correspondence should be addressed. E-mail: (RW); (PR)
| | | | - Victoria L. Robinson
- Chemical and Biological Sciences, Defence Science and Technology Laboratory, Salisbury, United Kingdom
| | - Petra C.F. Oyston
- Chemical and Biological Sciences, Defence Science and Technology Laboratory, Salisbury, United Kingdom
| | - Rick W. Titball
- Chemical and Biological Sciences, Defence Science and Technology Laboratory, Salisbury, United Kingdom
| | - Peter L. Roach
- School of Chemistry, University of Southampton, Southampton, United Kingdom
- * To whom correspondence should be addressed. E-mail: (RW); (PR)
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20
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Abstract
A microfabricated flow cytometer has been developed for the analysis of micron-sized polymer beads onto which fluorescently labelled proteins have been immobilised. Fluorescence measurements were made on the beads as they flowed through the chip. Binding of antibodies to surface-immobilised antigens was quantitatively assayed using the device. Particles were focused through a detection zone in the centre of the flow channel using negative dielectrophoresis. Impedance measurements of the particles (at 703 kHz) were used to determine particle size and to trigger capture of the fluorescence signal. Antibody binding was measured by fluorescence at single and dual excitation wavelengths (532 nm and 633 nm). Fluorescence compensation techniques were implemented to correct for spectral overspill between optical detection channels. The data from the microfabricated flow cytometer was shown to be comparable to that of a commercial flow cytometer (BD-FACSAria).
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Affiliation(s)
- David Holmes
- School of Electronics and Computing Science, University of Southampton, Highfield, Southampton, UK SO17 1BJ.
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21
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Abstract
Thiamine is biosynthesized by combining two heterocyclic precursors. In Escherichia coli and other anaerobes, one of the heterocycles, 4-methyl-5-(beta-hydroxyethyl) thiazole phosphate, is biosynthesized from 1-deoxyxylulose-5-phosphate, tyrosine, and cysteine. Genetic evidence has identified thiH, thiG, thiS, and thiF as essential for thiazole biosynthesis in E. coli. In this paper, we describe the measurement of the thiazole phosphate-forming reaction using purified protein components. The activity is shown to require four proteins isolated as heterodimers: ThiGH and ThiFS. Reconstitution of the [4Fe-4S] cluster in ThiH was essential for activity, as was the use of ThiS in the thiocarboxylate form. Spectroscopic studies with ThiGH strongly suggested that S-adenosylmethionine (AdoMet) bound to the [4Fe-4S] cluster, which became more susceptible to reduction to the +1 state. Assays of thiazole phosphate formation showed that, in addition to the proteins, Dxp, tyrosine, AdoMet, and a reductant were required. The analysis showed that no more than 1 mol eq of thiazole phosphate was formed per ThiGH. Furthermore, for each mole of thiazole-P formed, 1 eq of AdoMet and 1 eq of tyrosine were utilized, and 1 eq of 5'-deoxyadenosine was produced. These results demonstrate that ThiH is a member of the "radical-AdoMet" family and support a mechanistic hypothesis in which AdoMet is reductively cleaved to yield a highly reactive 5'-deoxyadenosyl radical. This radical is proposed to abstract the phenolic hydrogen atom from tyrosine, and the resultant substrate radical cleaves to yield dehydroglycine, which is required by ThiG for the thiazole cyclization reaction.
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Affiliation(s)
- Marco Kriek
- Chemical Biology Section, School of Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, United Kingdom
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22
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Cavalli G, Banu S, Ranasinghe RT, Broder GR, Martins HFP, Neylon C, Morgan H, Bradley M, Roach PL. Multistep synthesis on SU-8: combining microfabrication and solid-phase chemistry on a single material. ACTA ACUST UNITED AC 2007; 9:462-72. [PMID: 17417911 DOI: 10.1021/cc060079p] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
SU-8 is an epoxy-novolac resin and a well-established negative photoresist for microfabrication and microengineering. The photopolymerized resist is an extremely highly crosslinked polymer showing outstanding chemical and physical robustness with residual surface epoxy groups amenable for chemical functionalization. In this paper we describe, for the first time, the preparation and surface modification of SU-8 particles shaped as microbars, the attachment of appropriate linkers, and the successful application of these particles to multistep solid-phase synthesis leading to oligonucleotides and peptides attached in an unambiguous manner to the support surface.
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Affiliation(s)
- Gabriel Cavalli
- School of Chemistry, Highfield Campus, University of Southampton, Southampton SO17 1BJ, UK
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23
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Howard-Jones AR, Elkins JM, Clifton IJ, Roach PL, Adlington RM, Baldwin JE, Rutledge PJ. Interactions of Isopenicillin N Synthase with Cyclopropyl-Containing Substrate Analogues Reveal New Mechanistic Insight,. Biochemistry 2007; 46:4755-62. [PMID: 17397141 DOI: 10.1021/bi062314q] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Isopenicillin N synthase (IPNS), a non-heme iron oxidase central to penicillin and cephalosporin biosynthesis, catalyzes an energetically demanding chemical transformation to produce isopenicillin N from the tripeptide delta-(l-alpha-aminoadipoyl)-l-cysteinyl-d-valine (ACV). We describe the synthesis of two cyclopropyl-containing tripeptide analogues, delta-(l-alpha-aminoadipoyl)-l-cysteinyl-beta-methyl-d-cyclopropylglycine and delta-(l-alpha-aminoadipoyl)-l-cysteinyl-d-cyclopropylglycine, designed as probes for the mechanism of IPNS. We have solved the X-ray crystal structures of these substrates in complex with IPNS and propose a revised mechanism for the IPNS-mediated turnover of these compounds. Relative to the previously determined IPNS-Fe(II)-ACV structure, key differences exist in substrate orientation and water occupancy, which allow for an explanation of the differences in reactivity of these substrates.
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24
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Affiliation(s)
- Paul Douglas
- School of Chemistry, University of Southampton, Southampton SO17 1BJ, UK
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25
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Douglas P, Kriek M, Bryant P, Roach PL. Lipoyl Synthase Inserts Sulfur Atoms into an Octanoyl Substrate in a Stepwise Manner. Angew Chem Int Ed Engl 2006. [DOI: 10.1002/ange.200601910] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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26
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Bryant P, Kriek M, Wood RJ, Roach PL. The activity of a thermostable lipoyl synthase from Sulfolobus solfataricus with a synthetic octanoyl substrate. Anal Biochem 2006; 351:44-9. [PMID: 16500612 DOI: 10.1016/j.ab.2006.01.023] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2005] [Revised: 12/06/2005] [Accepted: 01/11/2006] [Indexed: 11/25/2022]
Abstract
The protein lipoyl synthase (LipA) is essential for lipoic acid biosynthesis via sulfur insertions into a protein-bound octanoyl group. We have developed an in vitro assay for LipA using a synthetic tetrapeptide substrate, containing an N(epsilon)-octanoyl lysine residue, corresponding in sequence to the lipoyl binding domain of the E2 subunit of pyruvate dehydrogenase. A putative LipA from the hypothermophilic archaea Sulfolobus solfataricus was expressed in Escherichia coli and purified, and the activity was measured using this novel assay. The optimal temperature for the S. solfataricus LipA-dependent formation of the lipoyl group was found to be 60 degrees C.
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Affiliation(s)
- Penny Bryant
- School of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK
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27
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Abstract
Several methods for ultra high-throughput DNA sequencing are currently under investigation. Many of these methods yield very short blocks of sequence information (reads). Here we report on an analysis showing the level of genome sequencing possible as a function of read length. It is shown that re-sequencing and de novo sequencing of the majority of a bacterial genome is possible with read lengths of 20–30 nt, and that reads of 50 nt can provide reconstructed contigs (a contiguous fragment of sequence data) of 1000 nt and greater that cover 80% of human chromosome 1.
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Affiliation(s)
| | | | | | - Adam Prügel-Bennett
- School of Electronics and Computer Science, University of SouthamptonSouthampton SO17 1BJ, UK
| | | | | | - Mark Bradley
- School of Chemistry, University of EdinburghEdinburgh EH9 3JJ, UK
| | - Cameron Neylon
- To whom correspondence should be addressed. Tel: +44 23 8059 4164; Fax: +44 23 8059 6805;
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28
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Long AJ, Clifton IJ, Roach PL, Baldwin JE, Rutledge PJ, Schofield CJ. Structural Studies on the Reaction of Isopenicillin N Synthase with the Truncated Substrate Analogues δ-(l-α-aminoadipoyl)-l-cysteinyl-glycine and δ-(l-α-aminoadipoyl)-l-cysteinyl-d-alanine,. Biochemistry 2005; 44:6619-28. [PMID: 15850395 DOI: 10.1021/bi047478q] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Isopenicillin N synthase (IPNS), a non-heme iron(II)-dependent oxidase, catalyzes conversion of the tripeptide delta-(l-alpha-aminoadipoyl)-l-cysteinyl-d-valine (ACV) to bicyclic isopenicillin N (IPN), concomitant with the reduction of dioxygen to two molecules of water. Incubation of the "truncated"substrate analogues delta-(l-alpha-aminoadipoyl)-l-cysteinyl-glycine (ACG) and delta-(l-alpha-aminoadipoyl)-l-cysteinyl-d-alanine (ACA) with IPNS has previously been shown to afford acyclic products, in which the substrate cysteinyl residue has undergone a two-electron oxidation. We report X-ray crystal structures for the anaerobic IPNS/Fe(II)/ACG and IPNS/Fe(II)/ACA complexes, both in the absence and presence of the dioxygen analogue nitric oxide. The overall protein structures are very similar to those of the corresponding IPNS/Fe(II)/ACV complexes; however, significant differences are apparent in the vicinity of the active site iron. The structure of the IPNS/Fe(II)/ACG complex reveals that the C-terminal carboxylate of this substrate is oriented toward the active site iron atom, apparently hydrogen-bonded to an additional water ligand at the metal; this is a different binding mode to that observed in the IPNS/Fe(II)/ACV complex. ACA binds to the metal in a manner that is intermediate between those observed for ACV and ACG. The addition of NO to these complexes initiates conformational changes such that both the IPNS/Fe(II)/ACG/NO and IPNS/Fe(II)/ACA/NO structures closely resemble the IPNS/Fe(II)/ACV/NO complex. These results further demonstrate the feasibility of metal-centered rearrangements in catalysis by non-heme iron enzymes and provide insight into the delicate balance between hydrophilic-hydrophobic interactions and steric effects in the IPNS active site.
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29
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Wood RJ, Pascoe DD, Brown ZK, Medlicott EM, Kriek M, Neylon C, Roach PL. Optimized conjugation of a fluorescent label to proteins via intein-mediated activation and ligation. Bioconjug Chem 2004; 15:366-72. [PMID: 15025533 DOI: 10.1021/bc0341728] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Intein-mediated ligation provides a site-specific method for the attachment of molecular probes to proteins. The method is inherently flexible with regard to either the protein sequence or the attached probe, but practical difficulties have limited the widespread use of this valuable labeling system for the attachment of small- to medium-sized molecules. We report herein studies to improve the efficiency and practical application of these reactions, including the assembly of plasmids for the expression of target-intein fusion proteins and the analysis of their reaction with a fluorescent cysteine derivative under a range of conditions. Optimal ligation of the fluorophore to the target protein is critically dependent on the degree of oxidation of the fluorescent cysteine derivative. Efficient ligation has been achieved with freshly prepared fluorescent cysteine derivative under rigorously anaerobic conditions. Similar ligation yields have also been achieved using more practically convenient conditions including anaerobic reaction with addition of thiophenol, or aerobic reaction with the further addition of tricarboxyethylphosphine.
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Affiliation(s)
- Robert J Wood
- School of Chemistry, University of Southampton, Highfield, Southampton, Hampshire, UK
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30
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Abstract
The biosynthesis of thiamine in Escherichia coli requires the formation of an intermediate thiazole from tyrosine, 1-deoxy-d-xylulose-5-phosphate (Dxp), and cysteine using at least six structural proteins, ThiFSGH, IscS, and ThiI. We describe for the first time the reconstitution of thiazole synthase activity using cell-free extracts and proteins derived from adenosine-treated E. coli 83-1 cells. The addition of adenosine or adenine to growing cultures of Aerobacter aerogenes, Salmonella typhimurium, and E. coli has been shown previously to relieve the repression by thiamine of its own biosynthesis and increase the expression levels of the thiamine biosynthetic enzymes. By exploiting this effect, we show that the in vitro thiazole synthase activity of cleared lysates or desalted proteins from E. coli 83-1 cells is dependent upon the addition of purified ThiGH-His complex, tyrosine (but not cysteine or 1-deoxy-d-xylulose-5-phosphate), and an as yet unidentified intermediate present in the protein fraction from these cells. The activity is strongly stimulated by the addition of S-adenosylmethionine and NADPH.
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Affiliation(s)
- Roberta Leonardi
- School of Chemistry, University of Southampton, Southampton SO17 1BJ, United Kingdom
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31
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Long AJ, Clifton IJ, Roach PL, Baldwin JE, Schofield CJ, Rutledge PJ. Structural studies on the reaction of isopenicillin N synthase with the substrate analogue delta-(l-alpha-aminoadipoyl)-l-cysteinyl-d-alpha-aminobutyrate. Biochem J 2003; 372:687-93. [PMID: 12622704 PMCID: PMC1223433 DOI: 10.1042/bj20021627] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2002] [Revised: 03/04/2003] [Accepted: 03/06/2003] [Indexed: 11/17/2022]
Abstract
Isopenicillin N synthase (IPNS) is a non-haem iron(II) oxidase which catalyses the biosynthesis of isopenicillin N from the tripeptide delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-valine (ACV). Herein we report crystallographic studies to investigate the reaction of IPNS with the truncated substrate analogue delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-alpha-aminobutyrate (ACAb). It has been reported previously that this analogue gives rise to three beta-lactam products when incubated with IPNS: two methyl penams and a cepham. Crystal structures of the IPNS-Fe(II)-ACAb and IPNS-Fe(II)-ACAb-NO complexes have now been solved and are reported herein. These structures and modelling studies based on them shed light on the diminished product selectivity shown by IPNS in its reaction with ACAb and further rationalize the presence of certain key residues at the IPNS active site.
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Affiliation(s)
- Alexandra J Long
- The Dyson Perrins Laboratory and the Oxford Centre for Molecular Sciences, University of Oxford, South Parks Road, UK
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32
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Elkins JM, Rutledge PJ, Burzlaff NI, Clifton IJ, Adlington RM, Roach PL, Baldwin JE. Crystallographic studies on the reaction of isopenicillin N synthase with an unsaturated substrate analogue. Org Biomol Chem 2003; 1:1455-60. [PMID: 12926272 DOI: 10.1039/b212270g] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Isopenicillin N synthase (IPNS) catalyses conversion of the linear tripeptide delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-valine (ACV) to isopenicillin N (IPN), the central step in biosynthesis of the beta-lactam antibiotics. The unsaturated substrate analogue delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-vinylglycine (ACvG) has previously been incubated with IPNS and single product was isolated, a 2-alpha-hydroxymethyl isopenicillin N (HMPen), formed via a monooxygenase mode of reactivity. ACvG has now been crystallised with IPNS and the structure of the anaerobic IPNS:Fe(II):ACvG complex determined to 1.15 A resolution. Furthermore, by exposing the anaerobically grown crystals to high-pressure oxygen gas, a structure corresponding to the bicyclic product HMPen has been obtained at 1.60 A resolution. In light of these and other IPNS structures, and recent developments with related dioxygenases, the [2 + 2] cycloaddition mechanism for HMPen formation from ACvG has been revised, and a stepwise radical mechanism is proposed. This revised mechanism remains consistent with the observed stereospecificity of the transformation, but fits better with apparent constraints on the coordination geometry around the active site iron atom.
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Affiliation(s)
- Jonathan M Elkins
- Dyson Perrins Laboratory, Oxford Centre for Molecular Sciences, University of Oxford, South Parks Road, Oxford, UK OX1 3QY
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33
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Kriek M, Peters L, Takahashi Y, Roach PL. Effect of iron-sulfur cluster assembly proteins on the expression of Escherichia coli lipoic acid synthase. Protein Expr Purif 2003; 28:241-5. [PMID: 12699687 DOI: 10.1016/s1046-5928(02)00680-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Lipoic Acid Synthase (LipA) can accommodate a [4Fe-4S] cluster that is thought to be essential for the insertion of sulfur into an octanoyl substrate during the biosynthesis of lipoic acid. With the objective of improving soluble holo-LipA expression, a series of multi-cistronic plasmids were constructed carrying lipA in combination with one of the three systems: groE/SL, trxA, or the isc operon. Co-expression of lipA with the isc operon approximately trebled the isolated yield of soluble LipA and resulted in efficient assembly of the Fe-S cluster. This strategy may be helpful in the soluble expression of a wide range of Fe-S cluster-dependent proteins.
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Affiliation(s)
- Marco Kriek
- Department of Chemistry, Southampton University, Highfield, Southampton SO17 1BJ, UK
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34
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Leonardi R, Fairhurst SA, Kriek M, Lowe DJ, Roach PL. Thiamine biosynthesis in Escherichia coli: isolation and initial characterisation of the ThiGH complex. FEBS Lett 2003; 539:95-9. [PMID: 12650933 DOI: 10.1016/s0014-5793(03)00204-7] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In Escherichia coli, two of the proteins required for the biosynthesis of the thiazole moiety of thiamine (vitamin B(1)) are ThiG and ThiH, encoded as part of the thiCEFSGH operon. In this study, a C-terminally hexahistidine-tagged ThiH (ThiH-His) was expressed in E. coli as a soluble protein from thiGH-His-tag and thiFSGH-His-tag-bearing plasmids. When isolated under anaerobic conditions, ThiG and ThiH-His co-purify as a large multimeric non-covalent complex. Electron paramagnetic resonance and UV-visible spectroscopy together with iron and sulfide analyses revealed the presence of an iron-sulfur cluster within this complex.
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Affiliation(s)
- Roberta Leonardi
- Department of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ, UK
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35
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Abstract
A system has been developed for subjecting protein crystals to hyperbaric pressures of oxygen gas in order to promote enzymatic reaction. Crystals of an oxygenase or oxidase enzyme are grown anaerobically by hanging drop vapor diffusion, under crystallization conditions modified to eliminate combustible materials such as plastic coverslips and grease. The crystalline enzyme:substrate complex can then be exposed to oxygen gas at pressures up to 60 bar using a custom-built device or "bomb." In this way, reaction is initiated synchronously throughout the crystal and subsequent flash freezing allows the trapping of enzyme:product complexes in high occupancy. These complexes can then be structurally characterized by conventional monochromatic X-ray crystallography. The bomb is furnished from naval brass and lubricated with Fomblin RT15 perfluorinated polyether grease in order to ensure compatibility with the highly oxidizing environment.
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Affiliation(s)
- Peter J Rutledge
- The Dyson Perrins Laboratory and the Oxford Centre for Molecular Sciences, University of Oxford, UK.
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36
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Elkins JM, Ryle MJ, Clifton IJ, Dunning Hotopp JC, Lloyd JS, Burzlaff NI, Baldwin JE, Hausinger RP, Roach PL. X-ray crystal structure of Escherichia coli taurine/alpha-ketoglutarate dioxygenase complexed to ferrous iron and substrates. Biochemistry 2002; 41:5185-92. [PMID: 11955067 DOI: 10.1021/bi016014e] [Citation(s) in RCA: 165] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Taurine/alpha-ketoglutarate dioxygenase (TauD), a non-heme Fe(II) oxygenase, catalyses the conversion of taurine (2-aminoethanesulfonate) to sulfite and aminoacetaldehyde concurrent with the conversion of alpha-ketoglutarate (alphaKG) to succinate and CO(2). The enzyme allows Escherichia coli to use taurine, widely available in the environment, as an alternative sulfur source. Here we describe the X-ray crystal structure of TauD complexed to Fe(II) and both substrates, alphaKG and taurine. The tertiary structure and fold of TauD are similar to those observed in other enzymes from the broad family of Fe(II)/alphaKG-dependent oxygenases, with closest structural similarity to clavaminate synthase. Using the TauD coordinates, a model was determined for the closely related enzyme 2,4-dichlorophenoxyacetate/alphaKG dioxygenase (TfdA), supporting predictions derived from site-directed mutagenesis and other studies of that biodegradative protein. The TauD structure and TfdA model define the metal ligands and the positions of nearby aromatic residues that undergo post-translational modifications involving self-hydroxylation reactions. The substrate binding residues of TauD were identified and those of TfdA predicted. These results, along with sequence alignment information, reveal how TauD selects a tetrahedral substrate anion in preference to the planar carboxylate selected by TfdA, providing insight into the mechanism of enzyme catalysis.
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Affiliation(s)
- Jonathan M Elkins
- Dyson Perrins Laboratory, Oxford University, South Parks Road, Oxford, England, OX1 3QY, and Departments of Microbiology & Molecular Genetics and Biochemistry & Molecular Biology, Michigan State University, East Lansing, Michigan 48824-1011
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37
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Hewitson KS, Ollagnier-de Choudens S, Sanakis Y, Shaw NM, Baldwin JE, Münck E, Roach PL, Fontecave M. The iron-sulfur center of biotin synthase: site-directed mutants. J Biol Inorg Chem 2002; 7:83-93. [PMID: 11862544 DOI: 10.1007/s007750100268] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2001] [Accepted: 05/17/2001] [Indexed: 11/26/2022]
Abstract
Biotin synthase contains an essential [4Fe-4S]+ cluster that is thought to provide an electron for the cleavage of S-adenosylmethionine, a cofactor required for biotin formation. The conserved cysteine residues Cys53, Cys57 and Cys60 have been proposed as ligands to the [4Fe-4S] cluster. These residues belong to a C-X3-C-X2-C motif which is also found in pyruvate formate lyase-activating enzyme, lysine 2,3-aminomutase and the anaerobic ribonucleotide reductase-activating component. To investigate the role of the cysteine residues, Cys-->Ala mutants of the eight cysteine residues of Escherichia coli biotin synthase were prepared and assayed for activity. Our results show that six cysteines are important for biotin formation. Only two mutant proteins, C276A and C288A, closely resembled the wild-type protein, indicating that the corresponding cysteines are not involved in iron chelation and biotin formation. The six other mutant proteins, C53A, C57A, C60A, C97A, C128A and C188A, were inactive but capable of assembling a [4Fe-4S] cluster, as shown by Mössbauer spectroscopy. The C53A, C57A and C60A mutant proteins are unique in that their cluster could not undergo reduction to the [4Fe-4S]+ state, as shown by EPR and Mössbauer spectroscopy. On this basis and by analogy with pyruvate formate lyase-activating enzyme and the anaerobic ribonucleotide reductase-activating component, it is suggested that the corresponding cysteines coordinate the cluster even though one cannot fully exclude the possibility that other cysteines play that role as well. Therefore it appears that for activity biotin synthase absolutely requires cysteines that are not involved in iron chelation.
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Affiliation(s)
- Kirsty S Hewitson
- Oxford Center for Molecular Sciences, Dyson Perrins Laboratory, South Parks Road, Oxford OX1 3QY, UK
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38
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Ogle JM, Clifton IJ, Rutledge PJ, Elkins JM, Burzlaff NI, Adlington RM, Roach PL, Baldwin JE. Alternative oxidation by isopenicillin N synthase observed by X-ray diffraction. Chem Biol 2001; 8:1231-7. [PMID: 11755401 DOI: 10.1016/s1074-5521(01)00090-4] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
BACKGROUND Isopenicillin N synthase (IPNS) catalyses formation of bicyclic isopenicillin N, precursor to all penicillin and cephalosporin antibiotics, from the linear tripeptide delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-valine. IPNS is a non-haem iron(II)-dependent enzyme which utilises the full oxidising potential of molecular oxygen in catalysing the bicyclisation reaction. The reaction mechanism is believed to involve initial formation of the beta-lactam ring (via a thioaldehyde intermediate) to give an iron(IV)-oxo species, which then mediates closure of the 5-membered thiazolidine ring. RESULTS Here we report experiments employing time-resolved crystallography to observe turnover of an isosteric substrate analogue designed to intercept the catalytic pathway at an early stage. Reaction in the crystalline enzyme-substrate complex was initiated by the application of high-pressure oxygen, and subsequent flash freezing allowed an oxygenated product to be trapped, bound at the iron centre. A mechanism for formation of the observed thiocarboxylate product is proposed. CONCLUSIONS In the absence of its natural reaction partner (the N-H proton of the L-cysteinyl-D-valine amide bond), the proposed hydroperoxide intermediate appears to attack the putative thioaldehyde species directly. These results shed light on the events preceding beta-lactam closure in the IPNS reaction cycle, and enhance our understanding of the mechanism for reaction of the enzyme with its natural substrate.
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Affiliation(s)
- J M Ogle
- The Dyson Perrins Laboratory, University of Oxford, UK
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39
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Birch OM, Hewitson KS, Fuhrmann M, Burgdorf K, Baldwin JE, Roach PL, Shaw NM. MioC is an FMN-binding protein that is essential for Escherichia coli biotin synthase activity in vitro. J Biol Chem 2000; 275:32277-80. [PMID: 10913144 DOI: 10.1074/jbc.m004497200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Biotin synthase is required for the conversion of dethiobiotin to biotin and requires a number of accessory proteins and small molecule cofactors for activity in vitro. We have previously identified two of these proteins as flavodoxin and ferredoxin (flavodoxin) NADP(+) reductase. We now report the identification of MioC as a third essential protein, together with its cloning, purification, and characterization. Purified MioC has a UV-visible spectrum characteristic of a flavoprotein and contains flavin mononucleotide. The presence of flavin mononucleotide and the primary sequence similarity to flavodoxin suggest that MioC may function as an electron transport protein. The role of MioC in the biotin synthase reaction is discussed, and the structure and function of MioC is compared with that of flavodoxin.
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Affiliation(s)
- O M Birch
- Biotechnology Research, Lonza A.G., CH-3930 Visp, Switzerland, Dyson Perrins Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QY, United Kingdom
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40
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Abstract
Biotin synthase (BioB) is a member of a family of enzymes that includes anaerobic ribonucleotide reductase and pyruvate formate lyase activating enzyme. These enzymes all use S-adenosylmethionine during turnover and contain three highly conserved cysteine residues that may act as ligands to an iron-sulfur cluster required for activity. Three mutant enzymes of BioB have been made, each with one cysteine residue (C53, 57, 60) mutated to alanine. All three mutant enzymes were inactive, but they still exhibited the characteristic UV-visible spectrum of a [2Fe-2S]2+ cluster similar to that of the wild-type enzyme.
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Affiliation(s)
- K S Hewitson
- Dyson Perrins Laboratory, University of Oxford, UK
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41
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Burzlaff NI, Rutledge PJ, Clifton IJ, Hensgens CM, Pickford M, Adlington RM, Roach PL, Baldwin JE. The reaction cycle of isopenicillin N synthase observed by X-ray diffraction. Nature 1999; 401:721-4. [PMID: 10537113 DOI: 10.1038/44400] [Citation(s) in RCA: 157] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Isopenicillin N synthase (IPNS), a non-haem iron-dependent oxidase, catalyses the biosynthesis of isopenicillin N (IPN), the precursor of all penicillins and cephalosporins. The key steps in this reaction are the two iron-dioxygen-mediated ring closures of the tripeptide delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-valine (ACV). It has been proposed that the four-membered beta-lactam ring forms initially, associated with a highly oxidized iron(iv)-oxo (ferryl) moiety, which subsequently mediates closure of the five-membered thiazolidine ring. Here we describe observation of the IPNS reaction in crystals by X-ray crystallography. IPNS Fe2+ substrate crystals were grown anaerobically, exposed to high pressures of oxygen to promote reaction and frozen, and their structures were elucidated by X-ray diffraction. Using the natural substrate ACV, this resulted in the IPNS x Fe2+ x IPN product complex. With the substrate analogue, delta-(L-alpha-aminoadipoyl)-L-cysteinyl-L-S-methylcysteine (ACmC) in the crystal, the reaction cycle was interrupted at the monocyclic stage. These mono- and bicyclic structures support our hypothesis of a two-stage reaction sequence leading to penicillin. Furthermore, the formation of a monocyclic sulphoxide product from ACmC is most simply explained by the interception of a high-valency iron-oxo species.
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Affiliation(s)
- N I Burzlaff
- The Dyson Perrins Laboratory and the Oxford Centre for Molecular Sciences, University of Oxford, UK
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42
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Roach PL, Clifton IJ, Hensgens CM, Shibata N, Schofield CJ, Hajdu J, Baldwin JE. Structure of isopenicillin N synthase complexed with substrate and the mechanism of penicillin formation. Nature 1997; 387:827-30. [PMID: 9194566 DOI: 10.1038/42990] [Citation(s) in RCA: 322] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The biosynthesis of penicillin and cephalosporin antibiotics in microorganisms requires the formation of the bicyclic nucleus of penicillin. Isopenicillin N synthase (IPNS), a non-haem iron-dependent oxidase, catalyses the reaction of a tripeptide, delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-valine (ACV), and dioxygen to form isopenicillin N and two water molecules. Mechanistic studies suggest the reaction is initiated by ligation of the substrate thiolate to the iron centre, and proceeds through an enzyme-bound monocyclic intermediate. Here we report the crystal structure of IPNS complexed to ferrous iron and ACV, determined to 1.3 A resolution. Based on the structure, we propose a mechanism for penicillin formation that involves ligation of ACV to the iron centre, creating a vacant iron coordination site into which dioxygen can bind. Subsequently, iron-dioxygen and iron-oxo species remove the requisite hydrogens from ACV without the direct assistance of protein residues. The crystal structure of the complex with the dioxygen analogue, NO and ACV bound to the active-site iron supports this hypothesis.
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Affiliation(s)
- P L Roach
- The Dyson Perrins Laboratory, University of Oxford, UK
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43
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Wilmouth RC, Clifton IJ, Robinson CV, Roach PL, Aplin RT, Westwood NJ, Hajdu J, Schofield CJ. Structure of a specific acyl-enzyme complex formed between beta-casomorphin-7 and porcine pancreatic elastase. Nat Struct Biol 1997; 4:456-62. [PMID: 9187653 DOI: 10.1038/nsb0697-456] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Mass spectrometric screening reveals that an unmodified natural heptapeptide--human beta-casomorphin-7, an internal sequence of human beta-casein that possesses opioid-like activity--reacts with porcine pancreatic elastase to form an unusually stable acyl-enzyme complex at low pH. X-ray crystallographic analysis (to 1.9 A resolution) at pH 5 shows continuous electron density linking the C-terminal isoleucine of beta-casomorphin-7 to Ser 195 through an ester bond. The structure reveals a well defined water molecule (Wat 317), equidistant between the carbon of the ester carbonyl and N epsilon 2 of His 57. Deprotonation of Wat 317 will produce a hydroxide ion positioned to attack the ester carbonyl through the favoured Bürgi-Dunitz trajectory.
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44
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Abstract
The non-heme ferrous dependent oxidase isopenicillin N synthase (IPNS) catalyses the biosynthesis of isopenicillin N from a tripeptide substrate. The crystal structure of Aspergillus nidulans IPNS complexed to manganese reveals a six co-ordinate metal ligated by two water molecules and four protein ligands: His-214, His-270, Asp-216 and Gln-330 (the penultimate C-terminal residue). Modification of Gln-330 to Ala or Leu, or deletion of 2 or 6 residues from the C-terminus resulted in lowering of specific activity; no activity was observed after deletion of 8 residues. The results demonstrate that metal ligation by Gln-330 is not required for catalytic activity.
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Affiliation(s)
- M Sami
- Dyson Perrins Laboratory and the Oxford Center for Molecular Sciences, UK
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45
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Barlow JN, Baldwin JE, Clifton IJ, Gibson E, Hensgens CM, Hajdu J, Hara T, Hassan A, John P, Lloyd MD, Roach PL, Prescott A, Robinson JK, Zhang ZH, Schofield CJ. Studies on non-haem ferrous-dependent oxygenases and oxidases. Biochem Soc Trans 1997; 25:86-90. [PMID: 9056849 DOI: 10.1042/bst0250086] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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46
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Roach PL, Clifton IJ, Hensgens CM, Shibata N, Long AJ, Strange RW, Hasnain SS, Schofield CJ, Baldwin JE, Hajdu J. Anaerobic crystallisation of an isopenicillin N synthase.Fe(II).substrate complex demonstrated by X-ray studies. Eur J Biochem 1996; 242:736-40. [PMID: 9022704 DOI: 10.1111/j.1432-1033.1996.0736r.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Isopenicillin N synthase (IPNS) was cocrystallised with ferrous sulphate and its substrate, delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-valine (Aad-Cys-Val). Vital to the successful procedure was the maintenance of a rigorously anaerobic environment. Hanging-drop vapour-diffusion crystallisation experiments, using lithium sulphate as the precipitant produced three crystal forms. Form I crystals, with a plate habit, diffracted X-rays to at least 0.11-nm resolution at the European Synchrotron Radiation Facility and belong to the space group P2(1)2(1)2(1), with unit-cell dimensions a = 4.68, b = 7.15, c = 10.10 nm. Their asymmetric unit contains a single IPNS.Fe(II).Aad-Cys-Val complex with a solvent content of 38.5%. Form II crystals, with a hexagonal habit, diffract X-rays to at least 0.21 nm resolution at the European Synchrotron Radiation Facility and belong to the space group P3(1)21, with unit-cell dimensions a = 10.10, b = 10.10, c = 11.567 nm. Their asymmetric unit also contains a single IPNS.Fe(II).Aad-Cys-Val complex with a solvent content of 69.5%. Form III crystals, needles, do not show well-ordered diffraction. Although all three forms were initially produced in crystallisation experiments under identical conditions, appropriate micro and streak seeding allows selective crystallisation of form I or form II crystals. Extended X-ray-absorption fine-structure studies on a crystalline slurry of the form I crystals demonstrate the presence of an Fe-S(Aad-Cys-Val) bond length of 0.234 +/- 0.003 nm.
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Affiliation(s)
- P L Roach
- Dyson Perrins Laboratory, University of Oxford, UK
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47
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Roach PL, Clifton IJ, Fülöp V, Harlos K, Barton GJ, Hajdu J, Andersson I, Schofield CJ, Baldwin JE. Crystal structure of isopenicillin N synthase is the first from a new structural family of enzymes. Nature 1995; 375:700-4. [PMID: 7791906 DOI: 10.1038/375700a0] [Citation(s) in RCA: 329] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Penicillin antibiotics are all produced from fermentation-derived penicillins because their chemical synthesis is not commercially viable. The key step in penicillin biosynthesis, in which both the beta-lactam and thiazolidine rings of the nucleus are created, is mediated by isopenicillin N synthase (IPNS), which binds ferrous iron and uses dioxygen as a cosubstrate. In a unique enzymatic step, with no chemical precedent, IPNS catalyses the transfer of four hydrogen atoms from its tripeptide substrate to dioxygen forming, in a single reaction, the complete bicyclic nucleus of the penicillins. We now report the structure of IPNS complexed with manganese, which reveals the active site is unusually buried within a 'jelly-roll' motif and lined by hydrophobic residues, and suggest how this structure permits the process of penicillin formation. Sequence analyses indicate IPNS, 1-aminocyclopropane-1-carboxylic acid oxidase and many of the 2-oxo-acid-dependent oxygenases contain a conserved jelly-roll motif, forming a new structural family of enzymes.
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Affiliation(s)
- P L Roach
- Dyson Perrins Laboratory, University of Oxford, UK
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48
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Roach PL, Schofield CJ, Baldwin JE, Clifton IJ, Hajdu J. Crystallization and preliminary X-ray diffraction studies on recombinant isopenicillin N synthase from Aspergillus nidulans. Protein Sci 1995; 4:1007-9. [PMID: 7663335 PMCID: PMC2143123 DOI: 10.1002/pro.5560040521] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Recombinant Aspergillus nidulans isopenicillin N synthase was purified from an Escherichia coli expression system. The apoenzyme in the presence of saturating concentrations of MnCl2 could be crystallized by either macro- or microseeding, using the hanging drop vapor diffusion technique with polyethylene glycol 8000 as precipitant. The crystals (0.5-1.0 mm overall dimensions) diffract X-rays to at least 2.0 A resolution at synchrotrons and belong to space group P212121 with unit cell dimensions of a = 59.2 A, b = 127.0 A, and c = 139.6 A. The asymmetric unit contains one dimer, and the solvent content of the crystals is 60%. The crystals are radiation sensitive.
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Affiliation(s)
- P L Roach
- Dyson Perrins Laboratory, University of Oxford, United Kingdom
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49
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Roach PL, Baldwin JE, Aplin RT, Robinson CV, Schofield CJ. Peptide mapping of the active site of Bacillus cereusβ-lactamase I by the use of high pressure liquid chromatography coupled to electrospray ionisation mass spectrometry. ACTA ACUST UNITED AC 1994. [DOI: 10.1039/c39940000849] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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50
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Aplin RT, Baldwin JE, Roach PL, Robinson CV, Schofield CJ. Investigations into the post-translational modification and mechanism of isopenicillin N:acyl-CoA acyltransferase using electrospray mass spectrometry. Biochem J 1993; 294 ( Pt 2):357-63. [PMID: 8396910 PMCID: PMC1134462 DOI: 10.1042/bj2940357] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Electrospray mass spectrometry (e.s.m.s.) was used to confirm the position of the post-translational cleavage of the isopenicillin N:acyl-CoA acyltransferase preprotein to give the alpha- and beta-subunits. The e.s.m.s. studies suggested partial modification of the alpha-subunit in vivo by exogenously added substituted acetic acids. E.s.m.s. has also allowed the observation in vitro of the transfer of the acyl group from several acyl-CoAs to the beta-subunit. N.m.r. data for the CoA species have been deposited as Supplementary Publication SUP 500173 (2 pages) at the British Library Document Supply Centre (DSC), Boston Spa, Wetherby, West Yorkshire LS23 7BQ, from whom copies can be obtained on the terms indicated in Biochem. J. (1993) 289, 9.
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Affiliation(s)
- R T Aplin
- Dyson Perrins Laboratory, Oxford, U.K
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