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Kormanec J, Novakova R, Csolleiova D, Feckova L, Rezuchova B, Sevcikova B, Homerova D. The antitumor antibiotic mithramycin: new advanced approaches in modification and production. Appl Microbiol Biotechnol 2020; 104:7701-7721. [DOI: 10.1007/s00253-020-10782-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 06/30/2020] [Accepted: 07/07/2020] [Indexed: 12/15/2022]
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Zabala D, Song L, Dashti Y, Challis GL, Salas JA, Méndez C. Heterologous reconstitution of the biosynthesis pathway for 4-demethyl-premithramycinone, the aglycon of antitumor polyketide mithramycin. Microb Cell Fact 2020; 19:111. [PMID: 32448325 PMCID: PMC7247220 DOI: 10.1186/s12934-020-01368-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 05/15/2020] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Mithramycin is an anti-tumor compound of the aureolic acid family produced by Streptomyces argillaceus. Its biosynthesis gene cluster has been cloned and characterized, and several new analogs with improved pharmacological properties have been generated through combinatorial biosynthesis. To further study these compounds as potential new anticancer drugs requires their production yields to be improved significantly. The biosynthesis of mithramycin proceeds through the formation of the key intermediate 4-demethyl-premithramycinone. Extensive studies have characterized the biosynthesis pathway from this intermediate to mithramycin. However, the biosynthesis pathway for 4-demethyl-premithramycinone remains unclear. RESULTS Expression of cosmid cosAR7, containing a set of mithramycin biosynthesis genes, in Streptomyces albus resulted in the production of 4-demethyl-premithramycinone, delimiting genes required for its biosynthesis. Inactivation of mtmL, encoding an ATP-dependent acyl-CoA ligase, led to the accumulation of the tricyclic intermediate 2-hydroxy-nogalonic acid, proving its essential role in the formation of the fourth ring of 4-demethyl-premithramycinone. Expression of different sets of mithramycin biosynthesis genes as cassettes in S. albus and analysis of the resulting metabolites, allowed the reconstitution of the biosynthesis pathway for 4-demethyl-premithramycinone, assigning gene functions and establishing the order of biosynthetic steps. CONCLUSIONS We established the biosynthesis pathway for 4-demethyl-premithramycinone, and identified the minimal set of genes required for its assembly. We propose that the biosynthesis starts with the formation of a linear decaketide by the minimal polyketide synthase MtmPKS. Then, the cyclase/aromatase MtmQ catalyzes the cyclization of the first ring (C7-C12), followed by formation of the second and third rings (C5-C14; C3-C16) catalyzed by the cyclase MtmY. Formation of the fourth ring (C1-C18) requires MtmL and MtmX. Finally, further oxygenation and reduction is catalyzed by MtmOII and MtmTI/MtmTII respectively, to generate the final stable tetracyclic intermediate 4-demethyl-premithramycinone. Understanding the biosynthesis of this compound affords enhanced possibilities to generate new mithramycin analogs and improve their production titers for bioactivity investigation.
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Affiliation(s)
- Daniel Zabala
- Departamento de Biología Funcional e Instituto Universitario de Oncología del Principado de Asturias (I.U.O.P.A), University of Oviedo, Oviedo, Spain
- Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK
| | - Lijiang Song
- Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK
| | - Yousef Dashti
- Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK
| | - Gregory L Challis
- Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK
- Warwick Integrative Synthetic Biology Centre, University of Warwick, Coventry, CV4 7AL, UK
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC, 3800, Australia
| | - José A Salas
- Departamento de Biología Funcional e Instituto Universitario de Oncología del Principado de Asturias (I.U.O.P.A), University of Oviedo, Oviedo, Spain
- Instituto de Investigación Sanitaria de Asturias (ISPA), Oviedo, Spain
| | - Carmen Méndez
- Departamento de Biología Funcional e Instituto Universitario de Oncología del Principado de Asturias (I.U.O.P.A), University of Oviedo, Oviedo, Spain.
- Instituto de Investigación Sanitaria de Asturias (ISPA), Oviedo, Spain.
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Wheeler R, Yu X, Hou C, Mitra P, Chen JM, Herkules F, Ivanov DN, Tsodikov OV, Rohr J. Discovery of a Cryptic Intermediate in Late Steps of Mithramycin Biosynthesis. Angew Chem Int Ed Engl 2019; 59:826-832. [PMID: 31702856 DOI: 10.1002/anie.201910241] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2019] [Revised: 10/14/2019] [Indexed: 12/23/2022]
Abstract
MtmOIV and MtmW catalyze the final two reactions in the mithramycin (MTM) biosynthetic pathway, the Baeyer-Villiger opening of the fourth ring of premithramycin B (PMB), creating the C3 pentyl side chain, strictly followed by reduction of the distal keto group on the new side chain. Unexpectedly this results in a C2 stereoisomer of mithramycin, iso-mithramycin (iso-MTM). Iso-MTM undergoes a non-enzymatic isomerization to MTM catalyzed by Mg2+ ions. Crystal structures of MtmW and its complexes with co-substrate NADPH and PEG, suggest a catalytic mechanism of MtmW. The structures also show that a tetrameric assembly of this enzyme strikingly resembles the ring-shaped β subunit of a vertebrate ion channel. We show that MtmW and MtmOIV form a complex in the presence of PMB and NADPH, presumably to hand over the unstable MtmOIV product to MtmW, yielding iso-MTM, as a potential self-resistance mechanism against MTM toxicity.
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Affiliation(s)
- Ryan Wheeler
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, 789 South Limestone Street, Lexington, KY, 40536-0596, USA
| | - Xia Yu
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, 789 South Limestone Street, Lexington, KY, 40536-0596, USA.,Xiangya School of Pharmaceutical Sciences, Central South University, Changsha, Hunan, 410013, P. R. China
| | - Caixia Hou
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, 789 South Limestone Street, Lexington, KY, 40536-0596, USA
| | - Prithiba Mitra
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, 789 South Limestone Street, Lexington, KY, 40536-0596, USA
| | - Jhong-Min Chen
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, 789 South Limestone Street, Lexington, KY, 40536-0596, USA
| | - Frank Herkules
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, TX, 78229, USA
| | - Dmitri N Ivanov
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, TX, 78229, USA
| | - Oleg V Tsodikov
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, 789 South Limestone Street, Lexington, KY, 40536-0596, USA
| | - Jürgen Rohr
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, 789 South Limestone Street, Lexington, KY, 40536-0596, USA
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Wheeler R, Yu X, Hou C, Mitra P, Chen J, Herkules F, Ivanov DN, Tsodikov OV, Rohr J. Discovery of a Cryptic Intermediate in Late Steps of Mithramycin Biosynthesis. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201910241] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Ryan Wheeler
- Department of Pharmaceutical SciencesCollege of PharmacyUniversity of Kentucky 789 South Limestone Street Lexington KY 40536-0596 USA
| | - Xia Yu
- Department of Pharmaceutical SciencesCollege of PharmacyUniversity of Kentucky 789 South Limestone Street Lexington KY 40536-0596 USA
- Xiangya School of Pharmaceutical SciencesCentral South University Changsha Hunan 410013 P. R. China
| | - Caixia Hou
- Department of Pharmaceutical SciencesCollege of PharmacyUniversity of Kentucky 789 South Limestone Street Lexington KY 40536-0596 USA
| | - Prithiba Mitra
- Department of Pharmaceutical SciencesCollege of PharmacyUniversity of Kentucky 789 South Limestone Street Lexington KY 40536-0596 USA
| | - Jhong‐Min Chen
- Department of Pharmaceutical SciencesCollege of PharmacyUniversity of Kentucky 789 South Limestone Street Lexington KY 40536-0596 USA
| | - Frank Herkules
- Department of BiochemistryUniversity of Texas Health Science Center San Antonio TX 78229 USA
| | - Dmitri N. Ivanov
- Department of BiochemistryUniversity of Texas Health Science Center San Antonio TX 78229 USA
| | - Oleg V. Tsodikov
- Department of Pharmaceutical SciencesCollege of PharmacyUniversity of Kentucky 789 South Limestone Street Lexington KY 40536-0596 USA
| | - Jürgen Rohr
- Department of Pharmaceutical SciencesCollege of PharmacyUniversity of Kentucky 789 South Limestone Street Lexington KY 40536-0596 USA
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Hill B, Jordan R, Qu Y, Assoud A, Rodrigo R. A common synthetic route to homochiral tetracycles related to pillaromycinone and premithramycinone. CAN J CHEM 2011. [DOI: 10.1139/v11-119] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Homochiral AB segments for (+)- and (–)-pillaromycinone were prepared in 11 steps from 2-acetylfuran. The synthesis featured an intramolecular Diels–Alder reaction of a 2,5-disubstituted furan and a hydroxyl-directed homogeneous hydrogenation of the tetrasubstituted alkene double bond of two enones. The CD segment was attached by a modified Staunton–Weinreb annulation to produce the desired homochiral tetracycle 21c related to (+)-pillaromycinone. An unusual acetonide migration enabled the synthesis of a tetracyclic model for premithramycinone.
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Affiliation(s)
- Bryan Hill
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Robert Jordan
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Yang Qu
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Abdeljalil Assoud
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Russell Rodrigo
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
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Baig I, Perez M, Braña AF, Gomathinayagam R, Damodaran C, Salas JA, Méndez C, Rohr J. Mithramycin analogues generated by combinatorial biosynthesis show improved bioactivity. JOURNAL OF NATURAL PRODUCTS 2008; 71:199-207. [PMID: 18197601 PMCID: PMC2442402 DOI: 10.1021/np0705763] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Plasmid pLNBIV was used to overexpress the biosynthetic pathway of nucleoside-diphosphate (NDP)-activated l-digitoxose in the mithramycin producer Streptomyces argillaceus. This led to a "flooding" of the biosynthetic pathway of the antitumor drug mithramycin (MTM) with NDP-activated deoxysugars, which do not normally occur in the pathway, and consequently to the production of the four new mithramycin derivatives 1- 4 with altered saccharide patterns. Their structures reflect that NDP sugars produced by pLNBIV, namely, l-digitoxose and its biosynthetic intermediates, influenced the glycosyl transfer to positions B, D, and E, while positions A and C remained unaffected. All four new structures have unique, previously not found sugar decoration patterns, which arise from either overcoming the substrate specificity or inhibition of certain glycosyltransferases (GTs) of the MTM pathway with the foreign NDP sugars expressed by pLNBIV. An apoptosis TUNEL (=terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) assay revealed that compounds 1 (demycarosyl-3D-beta- d-digitoxosyl-MTM) and 3 (deoliosyl-3C-beta- d-mycarosyl-MTM) show improved activity (64.8 +/- 2% and 50.3 +/- 2.5% induction of apoptosis, respectively) against the estrogen receptor (ER)-positive human breast cancer cell line MCF-7 compared with the parent drug MTM (37.8 +/- 2.5% induction of apoptosis). In addition, compounds 1 and 4 (3A-deolivosyl-MTM) show significant effects on the ER-negative human breast cancer cell line MDA-231 (63.6 +/- 2% and 12.6 +/- 2.5% induction of apoptosis, respectively), which is not inhibited by the parent drug MTM itself (2.6 +/- 1.5% induction of apoptosis), but for which chemotherapeutic agents are urgently needed.
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Affiliation(s)
- Irfan Baig
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, 725 Rose Street, Lexington, Kentucky 40536-0082, USA
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Zhang W, Watanabe K, Wang CCC, Tang Y. Investigation of early tailoring reactions in the oxytetracycline biosynthetic pathway. J Biol Chem 2007; 282:25717-25. [PMID: 17631493 DOI: 10.1074/jbc.m703437200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tetracyclines are aromatic polyketides biosynthesized by bacterial type II polyketide synthases. The amidated tetracycline backbone is biosynthesized by the minimal polyketide synthases and an amidotransferase homologue OxyD. Biosynthesis of the key intermediate 6-methylpretetramid requires two early tailoring steps, which are cyclization of the linearly fused tetracyclic scaffold and regioselective C-methylation of the aglycon. Using a heterologous host (CH999)/vector pair, we identified the minimum set of enzymes from the oxytetracycline biosynthetic pathway that is required to afford 6-methylpretetramid in vivo. Only two cyclases (OxyK and OxyN) are necessary to completely cyclize and aromatize the amidated tetracyclic aglycon. Formation of the last ring via C-1/C-18 aldol condensation does not require a dedicated fourth-ring cyclase, in contrast to the biosynthetic mechanism of other tetracyclic aromatic polyketides, such as daunorubicin and tetracenomycin. Acetyl-derived polyketides do not undergo spontaneous fourth-ring cyclization and form only anthracene carboxylic acids as demonstrated both in vivo and in vitro. OxyF was identified to be the C-6 C-methyltransferase that regioselectively methylates pretetramid to yield 6-methylpretetramid. Reconstitution of 6-methylpretetramid in a heterologous host sets the stage for a more systematic investigation of additional tetracycline downstream tailoring enzymes and is a key step toward the engineered biosynthesis of tetracycline analogs.
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Affiliation(s)
- Wenjun Zhang
- Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, California 90095, USA
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Abdelfattah MS, Rohr J. Premithramycinone G, an early shunt product of the mithramycin biosynthetic pathway accumulated upon inactivation of oxygenase MtmOII. Angew Chem Int Ed Engl 2007; 45:5685-9. [PMID: 16856198 PMCID: PMC4480643 DOI: 10.1002/anie.200600511] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Lombó F, Menéndez N, Salas JA, Méndez C. The aureolic acid family of antitumor compounds: structure, mode of action, biosynthesis, and novel derivatives. Appl Microbiol Biotechnol 2006; 73:1-14. [PMID: 17013601 DOI: 10.1007/s00253-006-0511-6] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2006] [Revised: 05/15/2006] [Accepted: 05/16/2006] [Indexed: 10/24/2022]
Abstract
Members of the aureolic acid family are tricyclic polyketides with antitumor activity which are produced by different streptomycete species. These members are glycosylated compounds with two oligosaccharide chains of variable sugar length. They interact with the DNA minor groove in high-GC-content regions in a nonintercalative way and with a requirement for magnesium ions. Mithramycin and chromomycins are the most representative members of the family, mithramycin being used as a chemotherapeutic agent for the treatment of several cancer diseases. For chromomycin and durhamycin A, antiviral activity has also been reported. The biosynthesis gene clusters for mithramycin and chromomycin A(3) have been studied in detail by gene sequencing, insertional inactivation, and gene expression. Most of the biosynthetic intermediates in these pathways have been isolated and characterized. Some of these compounds showed an increase in antitumor activity in comparison with the parent compounds. A common step in the biosynthesis of all members of the family is the formation of the tetracyclic intermediate premithramycinone. Further biosynthetic steps (glycosylation, methylations, acylations) proceed through tetracyclic intermediates which are finally converted into tricyclic compounds by the action of a monooxygenase, a key event for the biological activity. Heterologous expression of biosynthetic genes from other aromatic polyketide pathways in the mithramycin producer (or some mutants) led to the isolation of novel hybrid compounds.
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Affiliation(s)
- Felipe Lombó
- Departamento de Biología Funcional e Instituto Universitario de Oncología del Principado de Asturias (I.U.O.P.A), Universidad de Oviedo, 33006, Oviedo, Spain
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Abdelfattah MS, Rohr J. Premithramycinon G, ein frühes Shuntprodukt des Mithramycin-Biosyntheseweges, akkumuliert nach Inaktivierung der Oxygenase MtmOII. Angew Chem Int Ed Engl 2006. [DOI: 10.1002/ange.200600511] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Nur-e-Alam M, Méndez C, Salas JA, Rohr J. Elucidation of the glycosylation sequence of mithramycin biosynthesis: isolation of 3A-deolivosylpremithramycin B and its conversion to premithramycin B by glycosyltransferase MtmGII. Chembiochem 2005; 6:632-6. [PMID: 15712316 DOI: 10.1002/cbic.200400309] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Mohammad Nur-e-Alam
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, 725 Rose Street, Lexington, KY 40536-0082, USA
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Rodríguez D, Quirós LM, Salas JA. MtmMII-mediated C-Methylation during Biosynthesis of the Antitumor Drug Mithramycin Is Essential for Biological Activity and DNA-Drug Interaction. J Biol Chem 2004; 279:8149-58. [PMID: 14660589 DOI: 10.1074/jbc.m312351200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The antitumor drug mithramycin consists of a polyketide chromophore glycosylated with a trisaccharide and a disaccharide. Two post-polyketide methylations take place during mithramycin biosynthesis. One of these methylations has been shown to be very relevant for biological activity, that is the introduction of a methyl group at aromatic C-7. We have purified to 282- fold the MtmMII methyltransferase involved in this reaction. The protein is a monomer, and results from kinetic studies were consistent with a model for the enzyme acting via a compulsory order mechanism. The enzyme showed high substrate specificity and was unable to operate on structurally closely related molecules. Structural predictions suggest that the molecule is integrated by two domains, an essentially all alpha-amino domain and an alpha/beta-carboxyl domain displaying a variation of a Rossmann-fold containing the cofactor binding site. Although 7-demethyl-mithramycin did not show any biological activity, it was able to reach the nucleus of eukaryotic cells, with subsequent binding to DNA. Mithramycin and 7-demethylmithramycin were able to form similar complexes with Mg(2+), although their respective DNA binding isotherms were very different. The dinucleotide binding model fit well the isotherms recorded for both compounds, predicting that the C-7 methyl group was essential for high affinity binding to specific GC and CG sequences. Considering previous structural studies, we propose that this effect is performed by positioning the group in the floor of the minor groove, allowing the interaction with the third sugar moiety of the trisaccharide, d-mycarose, which is involved in sequence selectivity.
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Affiliation(s)
- David Rodríguez
- Departamento de Biologí Funcional, Universidad de Oviedo, 33006 Oviedo, Spain
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Kunnari T, Klika KD, Blanco G, Méndez C, Mäntsälä P, Hakala J, Sillanpää R, Tähtinen P, Salas J, Ylihonko K. Hybrid compounds generated by the introduction of a nogalamycin-producing plasmid into Streptomyces argillaceus. ACTA ACUST UNITED AC 2002. [DOI: 10.1039/b200444p] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Lozano MJ, Remsing LL, Quirós LM, Braña AF, Fernández E, Sánchez C, Méndez C, Rohr J, Salas JA. Characterization of two polyketide methyltransferases involved in the biosynthesis of the antitumor drug mithramycin by Streptomyces argillaceus. J Biol Chem 2000; 275:3065-74. [PMID: 10652287 DOI: 10.1074/jbc.275.5.3065] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A DNA chromosomal region of Streptomyces argillaceus ATCC 12596, the producer organism of the antitumor polyketide drug mithramycin, was cloned. Sequence analysis of this DNA region, located between four mithramycin glycosyltransferase genes, showed the presence of two genes (mtmMI and mtmMII) whose deduced products resembled S-adenosylmethionine-dependent methyltransferases. By independent insertional inactivation of both genes nonproducing mutants were generated that accumulated different mithramycin biosynthetic intermediates. The M3DeltaMI mutant (mtmMI-minus mutant) accumulated 4-demethylpremithramycinone (4-DPMC) which lacks the methyl groups at carbons 4 and 9. The M3DeltaM2 (mtmMII-minus mutant) accumulated 9-demethylpremithramycin A3 (9-DPMA3), premithramycin A1 (PMA1), and 7-demethylmithramycin, all of them containing the O-methyl group at C-4 and C-1', respectively, but lacking the methyl group at the aromatic position. Both genes were expressed in Streptomyces lividans TK21 under the control of the erythromycin resistance promoter (ermEp) of Saccharopolyspora erythraea. Cell-free extracts of these clones were precipitated with ammonium sulfate (90% saturation) and assayed for methylation activity using different mithramycin intermediates as substrates. Extracts of strains MJM1 (expressing the mtmMI gene) and MJM2 (expressing the mtmMII gene) catalyzed efficient transfer of tritium from [(3)H]S-adenosylmethionine into 4-DPMC and 9-DPMA3, respectively, being unable to methylate other intermediates at a detectable level. These results demonstrate that the mtmMI and mtmMII genes code for two S-adenosylmethionine-dependent methyltransferases responsible for the 4-O-methylation and 9-C-methylation steps of the biosynthetic precursors 4-DPMC and 9-DPMA3, respectively, of the antitumor drug mithramycin. A pathway is proposed for the last steps in the biosynthesis of mithramycin involving these methylation events.
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Affiliation(s)
- M J Lozano
- Departamento de Biología Funcional e Instituto Universitario de Oncología, Universidad de Oviedo, 33006 Oviedo, Spain
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Prado L, Fernández E, Weissbach U, Blanco G, Quirós LM, Braña AF, Méndez C, Rohr J, Salas JA. Oxidative cleavage of premithramycin B is one of the last steps in the biosynthesis of the antitumor drug mithramycin. CHEMISTRY & BIOLOGY 1999; 6:19-30. [PMID: 9889148 DOI: 10.1016/s1074-5521(99)80017-9] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
BACKGROUND Mithramycin is a member of the clinically important aureolic acid group of antitumor drugs that interact with GC-rich regions of DNA nonintercalatively. These drugs contain a chromophore aglycon that is derived from condensation of ten acetate units (catalyzed by a type II polyketide synthase). The aglycones are glycosylated at two positions with different chain length deoxyoligosaccharides, which are essential for the antitumor activity. During the early stages of mithramycin biosynthesis, tetracyclic intermediates of the tetracycline-type occur, which must be converted at later stages into the tricyclic glycosylated molecule, presumably through oxidative breakage of the fourth ring. RESULTS Two intermediates in the mithramycin biosynthetic pathway, 4-demethyl-premithramycinone and premithramycin B, were identified in a mutant lacking the mithramycin glycosyltransferase and methyltransferase genes and in the same mutant complemented with the deleted genes, respectively. Premithramycin B contains five deoxysugars moieties (like mithramycin), but contains a tetracyclic aglycon moiety instead of a tricyclic aglycon. We hypothesized that transcription of mtmOIV (encoding an oxygenase) was impaired in this strain, preventing oxidative breakage of the fourth ring of premithramycin B. Inactivating mtmOIV generated a mithramycin nonproducing mutant that accumulated premithramycin B instead of mithramycin. In vitro assays demonstrated that MtmOIV converted premithramycin B into a tricyclic compound. CONCLUSIONS In the late stages of mithramycin biosynthesis by Strepyomyces argillaceus, a fully glycosylated tetracyclic tetracycline-like intermediate (premithramycin B) is converted into a tricyclic compound by the oxygenase MtmOIV. This oxygenase inserts an oxygen (Baeyer-Villiger oxidation) and opens the resulting lactone. The following decarboxylation and ketoreduction steps lead to mithramycin. Opening of the fourth ring represents one of the last steps in mithramycin biosynthesis.
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Affiliation(s)
- L Prado
- Departamento de Biología Funcional e Instituto Universitario de Biotecnología de Asturias (IUBA-CSIC), Universidad de Oviedo, 33006 Oviedo, Spain
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Salas JA, Méndez C. Genetic manipulation of antitumor-agent biosynthesis to produce novel drugs. Trends Biotechnol 1998; 16:475-82. [PMID: 9830156 DOI: 10.1016/s0167-7799(98)01198-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Current methods of obtaining novel drugs may be complemented in the near future by the genetic engineering of antitumor-agent biosynthesis in microorganisms. Biosynthetic gene clusters from several antitumor pathways in actinomycetes are presently being characterized and expressed in order to generate novel drugs. Several novel hydroxylated and glycosylated antitumor-drug derivatives have been produced that show a relaxed substrate specificity for secondary-metabolic enzymes, which opens up the possibility of generating novel drugs by genetic manipulation.
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Affiliation(s)
- J A Salas
- Departamento de Biologia Funcional e Instituto Universitario de Biotecnologia de Asturias (IUBA-CSIC), Universidad de Oviedo, Spain.
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Fernández E, Weissbach U, Sánchez Reillo C, Braña AF, Méndez C, Rohr J, Salas JA. Identification of two genes from Streptomyces argillaceus encoding glycosyltransferases involved in transfer of a disaccharide during biosynthesis of the antitumor drug mithramycin. J Bacteriol 1998; 180:4929-37. [PMID: 9733697 PMCID: PMC107519 DOI: 10.1128/jb.180.18.4929-4937.1998] [Citation(s) in RCA: 160] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mithramycin is an antitumor polyketide drug produced by Streptomyces argillaceus that contains two deoxysugar chains, a disaccharide consisting of two D-olivoses and a trisaccharide consisting of a D-olivose, a D-oliose, and a D-mycarose. From a cosmid clone (cosAR3) which confers resistance to mithramycin in streptomycetes, a 3-kb PstI-XhoI fragment was sequenced, and two divergent genes (mtmGI and mtmGII) were identified. Comparison of the deduced products of both genes with proteins in databases showed similarities with glycosyltransferases and glucuronosyltransferases from different sources, including several glycosyltransferases involved in sugar transfer during antibiotic biosynthesis. Both genes were independently inactivated by gene replacement, and the mutants generated (M3G1 and M3G2) did not produce mithramycin. High-performance liquid chromatography analysis of ethyl acetate extracts of culture supernatants of both mutants showed the presence of several peaks with the characteristic spectra of mithramycin biosynthetic intermediates. Four compounds were isolated from both mutants by preparative high-performance liquid chromatography, and their structures were elucidated by physicochemical methods. The structures of these compounds were identical in both mutants, and the compounds are suggested to be glycosylated intermediates of mithramycin biosynthesis with different numbers of sugar moieties attached to C-12a-O of a tetracyclic mithramycin precursor and to C-2-O of mithramycinone: three tetracyclic intermediates containing one sugar (premithramycin A1), two sugars (premithramycin A2), or three sugars (premithramycin A3) and one tricyclic intermediate containing a trisaccharide chain (premithramycin A4). It is proposed that the glycosyltransferases encoded by mtmGI and mtmGII are responsible for forming and transferring the disaccharide during mithramycin biosynthesis. From the structures of the new metabolites, a new biosynthetic sequence regarding late steps of mithramycin biosynthesis can be suggested, a sequence which includes glycosyl transfer steps prior to the final shaping of the aglycone moiety of mithramycin.
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Affiliation(s)
- E Fernández
- Departamento de Biología Funcional e Instituto Universitario de Biotecnologia de Asturias, Universidad de Oviedo, 33006 Oviedo, Spain
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