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ABSTRACT: 9-Methylstreptimidone is a glutarimide antibiotic showing antiviral, antifungal, and antitumor activities. Genome scanning, bioinformatics analysis, and gene inactivation experiments reveal a gene cluster responsible for the biosynthesis of 9-methylstreptimidone in Streptomyces himastatinicus. The unveiled machinery features both acyltransferase- and thioesterase-less iterative use of module 5 as well as a branching module for glutarimide generation. Impressively, inactivation of smdK leads to a new carboxylate analogue unveiling a new mechanism for polyketide terminal diene formation.
Organic Letters 02/2013; · 5.86 Impact Factor
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ABSTRACT: Griseoviridin (GV) and viridogrisein (VG, also referred to as etamycin), produced by Streptomyces griseoviridis, are two chemically unrelated compounds belonging to the streptogramin family. Both of these natural products demonstrate broad-spectrum antibacterial activity and constitute excellent candidates for future drug development. To elucidate the biosynthetic machinery associated with production of these two unique antibiotics, the gene cluster responsible for both GV and VG production was identified within the Streptomyces griseoviridis genome and characterized, and its function in GV and VG biosynthesis was confirmed by inactivation of 30 genes and complementation experiments. This sgv gene cluster is localized to a 105 kb DNA region that consists of 36 open reading frames (ORFs), including four nonribosomal peptide synthetases (NRPSs) for VG biosynthesis and a set of hybrid polyketide synthases (PKS)-NRPSs with a discrete acyltransferase (AT), SgvQ, to assemble the GV backbone. The enzyme encoding genes for VG versus GV biosynthesis are separated into distinct "halves" of the cluster. A series of four genes: sgvA, sgvB, sgvC, and sgvK, were found downstream of the PKS-NRPS; these likely code for construction of a γ-butyrolactone (GBL)-like molecule. GBLs and the corresponding GBL receptor systems are the highest ranked regulators that are able to coordinate the two streptomyces antibiotic regulatory protein (SARP) family positive regulators SgvR2 and SgvR3; both are key biosynthetic activators. Models of GV, VG, and GBL biosynthesis were proposed by using functional gene assignments, determined on the basis of bioinformatics analysis and further supported by in vivo gene inactivation experiments. Overall, this work provides new insights into the biosyntheses of the GV and VG streptogramins that are potentially applicable to a host of combinatorial biosynthetic scenarios.
ChemBioChem 11/2012; · 3.94 Impact Factor
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ABSTRACT: Three new mycophenolic acid derivatives, penicacids A-C (1-3), together with two known analogues, mycophenolic acid (MPA, 4) and 4'-hydroxy-MPA (5), were isolated from a fungus Penicillium sp. SOF07 derived from a South China Sea marine sediment. The structures of compounds 1-3 were elucidated on the basis of MS and NMR ((1)H, (13)C, HSQC and HMBC) data analyses and comparisons with the known compounds. Structure-activity relationship studies of compounds 1-5 focused on inosine-monophosphate dehydrogenase inhibition revealed that hydroxylation at C-4', methylation at C-7-OH, dual hydroxylation at C-2'/C-3' double bond of MPA diminished bioactivity whereas glucosyl hydroxylation at C-4' correlated to bioactivity comparable to that observed for MPA.
Bioorganic & medicinal chemistry letters 03/2012; 22(9):3332-5. · 2.65 Impact Factor
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ABSTRACT: The nine-membered indolactam antibiotics belong to a small group of antibiotics showing broad biological activities. However, the in vivo genetic engineering of compounds of this type has not been performed. Here we report the identification of a single gene cluster responsible for the biosynthesis of methylpendolmycin and pendolmycin, two members of this family of antibiotics, from the deep sea bacterium Marinactinospora thermotolerans SCSIO 00652. Bioinformatics analysis and gene inactivation, coupled with metabolite characterization, reveal that MpnB, a nonribosomal peptide synthetase, MpnC, a cytochrome P450, and MpnD, a prenyltransferase, are sufficient to catalyze the biosynthesis of the two antibiotics from L-Ile (or L-Val), L-Trp, and methionine. MpnD is the first identified enzyme that transfers a C5 prenyl unit in a reverse manner to the C-7 position of a Trp-derived natural product.
ChemBioChem 03/2012; 13(4):547-52. · 3.94 Impact Factor
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Hongbo Huang,
Tingting Yang,
Xiangmei Ren,
Jing Liu,
Yongxiang Song,
Aijun Sun,
Junying Ma, Bo Wang,
Yun Zhang,
Caiguo Huang,
Changsheng Zhang,
Jianhua Ju
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ABSTRACT: Five new C-glycoside angucyclines, named grincamycins B-F (1-5), and a known angucycline antibiotic, grincamycin (6), were isolated from Streptomyces lusitanus SCSIO LR32, an actinomycete of deep sea origin. The structures of these compounds were elucidated on the basis of extensive spectroscopic analyses, including MS and 1D and 2D NMR experiments. All compounds except grincamycin F (5) exhibited in vitro cytotoxicities against the human cancer cell lines HepG2, SW-1990, HeLa, NCI-H460, and MCF-7 and the mouse melanoma cell line B16, with IC₅₀ values ranging from 1.1 to 31 μM.
Journal of Natural Products 02/2012; 75(2):202-8. · 3.13 Impact Factor
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ABSTRACT: The tirandamycins (TAMs) are a small group of Streptomyces-derived natural products that target bacterial RNA polymerase. Within the TAM biosynthetic cluster, trdE encodes a glycoside hydrolase whose role in TAM biosynthesis has been undefined until now. We report that in vivo trdE inactivation leads to accumulation of pre-tirandamycin, the earliest intermediate released from its mixed polyketide/nonribosomal peptide biosynthetic assembly line. In vitro and site-directed mutagenesis studies showed that TrdE, a putative glycoside hydrolase, catalyzes in a highly atypical fashion the installation of the Δ(11,12) double bond during TAM biosynthesis.
Journal of the American Chemical Society 02/2012; 134(6):2844-7. · 9.91 Impact Factor
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Qinghua Zhu,
Jun Li,
Junying Ma,
Minghe Luo, Bo Wang,
Hongbo Huang,
Xinpeng Tian,
Wenjun Li,
Si Zhang,
Changsheng Zhang,
Jianhua Ju
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ABSTRACT: Marinactinospora thermotolerans SCSIO 00652, originating from a deep-sea marine sediment of the South China Sea, was discovered to produce antimicrobial nucleoside antibiotic A201A. Whole-genome scanning and annotation strategies enabled us to localize the genes responsible for A201A biosynthesis and to experimentally identify the gene cluster; inactivation of mtdF, an oxidoreductase gene within the suspected gene cluster, abolished A201A production. Bioinformatics analysis revealed that a gene designated mtdA furthest upstream within the A201A biosynthetic gene cluster encodes a GntR family transcriptional regulator. To determine the role of MtdA in regulating A201A production, the mtdA gene was inactivated in frame and the resulting ΔmtdA mutant was fermented alongside the wild-type strain as a control. High-performance liquid chromatography (HPLC) analyses of fermentation extracts revealed that the ΔmtdA mutant produced A201A in a yield ∼25-fold superior to that of the wild-type strain, thereby demonstrating that MtdA is a negative transcriptional regulator governing A201A biosynthesis. By virtue of its high production capacity, the ΔmtdA mutant constitutes an ideal host for the efficient large-scale production of A201A. These results validate M. thermotolerans as an emerging source of antibacterial agents and highlight the efficiency of metabolic engineering for antibiotic titer improvement.
Antimicrobial Agents and Chemotherapy 11/2011; 56(1):110-4. · 4.84 Impact Factor
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Angewandte Chemie International Edition 07/2011; 50(34):7797-802. · 13.45 Impact Factor
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ABSTRACT: TrdL, encoding a flavin-dependent oxidoreductase in the tirandamycin gene cluster, was inactivated to afford a ΔtrdL mutant, the fermentation of which yielded a new intermediate, tirandamycin E (5), and an additional early intermediate, tirandamycin F (6), if XAD-16 resin was introduced. TrdL was overexpressed in E. coli, and the protein was shown to efficiently catalyze the transformations from 5 to tirandamycin A (1) and from 6 to tirandamycin D (4), demonstrating its function as a 10-hydroxy dehydrogenase.
Organic Letters 04/2011; 13(9):2212-5. · 5.86 Impact Factor
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ABSTRACT: Tirandamycins are bacterial RNA polymerase inhibitors holding great potential for antibacterial agent design. To elucidate the biosynthetic machinery and generate new derivatives, the tirandamycin biosynthetic gene cluster was cloned and sequenced from marine-derived Streptomyces sp. SCSIO1666. The biosynthetic gene cluster of tirandamycin spans a DNA region of ∼56kb and consists of 15 open reading frames (ORFs) which encode three type I polyketide synthases (TrdAI, AII, AIII), one non-ribosomal peptide synthetase (TrdD), one phosphopantetheinyl transferase (TrdM), one Type II thioesterase (TrdB), one FAD-dependent oxidoreductase (TrdL), one cytochrome P450 monooxygenase (TrdI), three proteins related to resistance and regulations (TrdHJK), and four proteins with unknown function (TrdCEFG). To investigate the roles of the genes played in the biosynthetic machinery, seven genes (trdAI and trdBDFHIK) were inactivated via in frame replacement with an apramycin gene cassette using λ-RED recombination technology. The ΔtrdAI and ΔtrdD mutants targeting the ketosynthase and adenylation domain of TrdAI and TrdD, respectively, abolished the production of tirandamycins, confirming their involvement in the tirandamycin biosynthesis. TrdH showed high homology to LuxR family transcriptional regulatory proteins, disruption of which abolished the production of tirandamycins, indicating that TrdH is a positive regulator for tirandamycin biosynthesis. On the other hand, TrdK showed high homology to TetR-family transcriptional regulatory proteins, disruption of which significantly increased the yields of tirandamycins almost one-fold, implicating that TrdK is a negative regulator for tirandamycin biosynthesis. Disruption of the gene trdI resulted in the accumulation of the intermediate tirandamycin C (3) and a trace amount of new product tirandamycin C2 (5). A model of tirandamycin biosynthesis was proposed based on bioinformatics analyses, gene inactivation experiments and intermediates isolated from the mutants. These findings set the stage for further study of the tirandamycin biosynthetic mechanism and rationally engineer new tirandamycin analogues.
Biochemical and Biophysical Research Communications 02/2011; 406(3):341-7. · 2.48 Impact Factor
