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At least 289 records · Page 16Linked to original sources
PubMed2007

Total synthesis, molecular editing and evaluation of a tripyrrolic natural product: the case of "butylcycloheptylprodigiosin".

Conflicting reports are found in the literature on whether the ortho-pyrrolophane derivative 6, which has been named "butylcycloheptylprodigiosin" even though it is a cyclononane derivative, is a natural product or merely a mis-assigned structure. This dispute has now been resolved by an unambiguous total synthesis of this complex alkaloid which confirms the initial structure assignment. The chosen approach is largely catalysis-based, featuring the first application of a "Narasaka-Heck" reaction in natural product chemistry. This palladium-catalyzed transformation allows the unsaturated oxime ester 26 to be converted into the bicyclic dihydropyrrole 27. Other notable reactions of the reported approach to 6 are a regioselective Tsuji-Trost reaction of the doubly allylic acetate 21 with methyl acetoacetate, a base-induced aromatization of 27 to the corresponding pyrrole 28, a chemoselective oxidation of the benzylic methyl group in 33 with cerium ammonium nitrate in a biphasic reaction medium that does not affect the labile pyrrole nucleus, and a Suzuki cross-coupling for the completion of the heterocyclic domain. Diversification in the latter step leads to a set of analogues that differ from the natural product in the terminal (hetero)arene ring. This structural modification results in complete loss of the very pronounced ability of the parent compound 6 to induce oxidative cleavage in double stranded DNA in the presence of Cu(II). Several cyclononane-, cyclononene- and cyclononadiene derivatives prepared en route to 6 have been characterized by crystal structure analysis, allowing the conformational behavior of nine-membered carbocycles to be studied.

Biochemistry↗
PubMed2002

Carbon flux distribution in antibiotic-producing chemostat cultures of Streptomyces lividans.

The carbon metabolism of derivatives of Streptomyces lividans growing under phosphate limitation in chemostat cultures and producing the antibiotics actinorhodin and undecylprodigiosin was investigated. By applying metabolic flux analysis to a stoichiometric model, the relationship between antibiotic production, biomass accumulation, and carbon flux through the major carbon metabolic pathways (the Embden Meyerhoff Parnas and pentose-phosphate pathways) was analyzed. Distribution of carbon flux through the catabolic pathways was shown to be dependent on growth rate, as well as on the carbon and energy source (glucose or gluconate) used. Increasing growth rates promoted an increase in the flux of carbon through glycolysis and the pentose-phosphate pathway. The synthesis of both actinorhodin and undecylprodigiosin was found to be inversely related to flux through the pentose-phosphate pathway.

Anthraquinones↗
PubMed1991

New classes of Streptomyces coelicolor A3(2) mutants blocked in undecylprodigiosin (Red) biosynthesis.

Fifteen mutants of Streptomyces coelicolor A3(2) blocked in both the bipyrrole branch (redA) and a second site specific to the undecylprodigiosin pathway were characterized. Some of the mutants were ordered biosynthetically based on cosynthesis experiments. Complementation of each of the mutants with wild-type DNA cloned in low- and high-copy number plasmid vectors allowed the mutants to be separated into 12 new classes which are physically clustered within approximately 37 kb on the S. coelicolor genome. Early-step biosynthetic genes are centrally located and are flanked by later-step and regulatory genes.

DNA, Bacterial↗
PubMed2004

A pair of two-component regulatory genes ecrA1/A2 in S. coelicolor.

Two-component genes are kinds of genetic elements involved in regulation of antibiotic production in Streptomyces coelicolor. DNA microarray analysis revealed that ecrA1/A2, which mapped at distant sites from red locus and encode respectively the kinase and regulator, expressed coordinately with genes of Red specific biosynthetic pathway. ecrA1 and ecrA2 gene-disruptive mutants were constructed using homogenotisation by reciprocal double crossover. Fermentation data showed that the undecylprodigiosin (Red) level of production was lower than that of wild-type strain. However, the change of the actinorhodin (Act) production level was not significant compared with wild type. Thus, these experiment results confirmed that the two-component system ecrA1/A2 was positive regulatory element for red gene cluster.

Anthraquinones↗
PubMed2003

Characterization of the Streptomyces coelicolor A3(2) wblE gene, encoding a homologue of the sporulation transcription factor.

The gene corresponding to the recently identified whiB-paralogous gene wblE in S. coelicolor was found after sequencing the downstream region of the stress-response sporulation-specific sigma-factor gene, sigH, in S. coelicolor A3(2). Sequence analysis has revealed an ORF exhibiting high similarity to sporulation transcription factors WhiB and WhiD. A stable null mutant of the wblE gene was obtained by integrative transformation, via double cross-over. Disruption of the S. coelicolor wblE gene appeared to have no obvious effect on growth, morphology, differentiation, and production of the pigmented antibiotics actinorhodin and undecylprodigiosin. Expression of the wblE gene was investigated during differentiation by S1 nuclease mapping, using RNA prepared from S. coelicolor A3(2) and its isogenic sigF and sigH mutants grown to various developmental stages. A single promoter was identified upstream of the wblE coding region. The wblEp promoter was induced at the beginning of aerial mycelium formation and its activity decreased later in differentiation. No differences in expression of the wblEp promoter were detected in S. coelicolor A3(2) mutants in sigF and sigH genes for sporulation-specific sigma factors. Sequence of the wblEp promoter showed partial similarity to the consensus sequence of the extracytoplasmic sigma factors.

Amino Acid Sequence↗
PubMed2002

A possible role of poly-3-hydroxybutyric acid in antibiotic production in Streptomyces.

The occurrence of poly-3-hydroxybutyric acid (PHB) in 12 different strains of the genus Streptomyces was investigated. Gas chromatographic estimation indicated that all the strains produced PHB and the range of maximum PHB accumulation was between 1.5 and 11.8% dry cell weight. PHB was isolated from Streptomyces coelicolor A3(2) M145 and characterized using Fourier transform-infrared (FT-IR) spectroscopy. The correlation between PHB utilization and antibiotic production in S. coelicolor A3(2) M145, was studied; results indicated a possible role of PHB as a carbon reserve material used for antibiotic production.

Anthraquinones↗
PubMed2004

Differential production of two antibiotics of Streptomyces coelicolor A3(2), actinorhodin and undecylprodigiosin, upon salt stress conditions.

Production of two pigmented antibiotics, actinorhodin and undecylprodigiosin, is differentially affected in Streptomyces coelicolor A3(2) at high salt concentration, with actinorhodin being inhibited and undecylprodigiosin activated. Analysis of expression of two genes coding for pathway-specific transcriptional regulators of actinorhodin and undecylprodigiosin synthesis, actII-ORF4 and redD, revealed that their expression is similarly differentially affected. Thus, the effect of high salt concentration on actinorhodin and undecylprodigiosin production is mediated at the transcriptional level by the differential expression of genes encoding corresponding pathway-specific transcriptional regulators.

Anthraquinones↗
PubMed2003

Deletion of scbA enhances antibiotic production in Streptomyces lividans.

Antibiotic production in many streptomycetes is influenced by extracellular gamma-butyrolactone signalling molecules. In this study, the gene scbA, which had been shown previously to be involved in the synthesis of the gamma-butyrolactone SCB1 in Streptomyces coelicolor A3(2), was deleted from the chromosome of Streptomyces lividans 66. Deletion of scbA eliminated the production of the antibiotic stimulatory activity previously associated with SCB1 in S. coelicolor. When the S. lividans scbA mutant was transformed with a multi-copy plasmid carrying the gene encoding the pathway-specific activator for either actinorhodin or undecylprodigiosin biosynthesis, production of the corresponding antibiotic was elevated significantly compared to the corresponding scbA(+) strain carrying the same plasmid. Consequently, deletion of scbA may be useful in combination with other strategies to construct host strains capable of improved bioactive metabolite production.

4-Butyrolactone↗
PubMed2005

A framework to analyze multiple time series data: a case study with Streptomyces coelicolor.

Transcriptional regulation in differentiating microorganisms is highly dynamic involving multiple and interwinding circuits consisted of many regulatory genes. Elucidation of these networks may provide the key to harness the full capacity of many organisms that produce natural products. A powerful tool evolved in the past decade is global transcriptional study of mutants in which one or more key regulatory genes of interest have been deleted. To study regulatory mutants of Streptomyces coelicolor, we developed a framework of systematic analysis of gene expression dynamics. Instead of pair-wise comparison of samples in different combinations, genomic DNA was used as a common reference for all samples in microarray assays, thus, enabling direct comparison of gene transcription dynamics across different isogenic mutants. As growth and various differentiation events may unfold at different rates in different mutants, the global transcription profiles of each mutant were first aligned computationally to those of the wild type, with respect to the corresponding growth and differentiation stages, prior to identification of kinetically differentially expressed genes. The genome scale transcriptome data from wild type and a DeltaabsA1 mutant of Streptomyces coelicolor were analyzed within this framework, and the regulatory elements affected by the gene knockout were identified. This methodology should find general applications in the analysis of other mutants in our repertoire and in other biological systems.

Anthraquinones↗
PubMed1990

Cloning and expression in a heterologous host of the complete set of genes for biosynthesis of the Streptomyces coelicolor antibiotic undecylprodigiosin.

A fragment of DNA carrying the hitherto unisolated members of the cluster of genes (red) for biosynthesis of the red-pigmented antibiotic undecylprodigiosin of Streptomyces coelicolor A3(2) was isolated. This was done by cloning random fragments of S. coelicolor DNA into the closely related Streptomyces lividans 66 and recovering a clone that caused overproduction of undecylprodigiosin. The effect was probably due to the presence of the cloned redD gene, which functions as a positive regulator of the expression of the red cluster, activating the normally poorly expressed red genes of S. lividans. Two fragments from either end of the red cluster were cloned adjacent to each other on a low-copy-number Streptomyces vector. Double crossing-over occurring between these plasmid-borne sequences and the chromosomal copy of the same DNA in S. coelicolor led to isolation of the entire red cluster as a single cloned fragment. Isolation of antibiotic biosynthetic genes by the effects of an activator in a self-cloning experiment, and in vivo reconstitution of a large cluster of genes by homologous recombination, may turn out to be usefully generalizable procedures.

Cloning, Molecular↗
PubMed1996

Characterization of spaA, a Streptomyces coelicolor gene homologous to a gene involved in sensing starvation in Escherichia coli.

A Streptomyces coelicolor gene, called spaA, homologous to the stationary phase regulatory gene rspA of Escherichia coli [Huisman and Kolter (1994) Science 265, 537-539], was cloned using the Streptomyces ambofaciens rspA homologue spa2 [Schneider et al. (1993) J. Gen. Microbiol. 139, 2559-2567] as a probe. Considerable differences in sequence and in genetic context were detected between spa2 of S. ambofaciens and spaA of S. coelicolor. A cloned internal fragment of spaA was used to direct integration of a phage vector into the spaA gene. The disruption caused delayed antibiotic production (undecylprodigiosin and actinorhodin) and led on further incubation to increased actinorhodin production at high, but not low, cell density. This phenotype was apparent only on the nutritionally poorest of three media tested. The attempted use of an integrating plasmid-based system for gene replacement of spaA gave rise to extensive deletions of adjacent chromosomal DNA.

Amino Acid Sequence↗
PubMed1993

Physiology and genetics of antibiotic production and resistance.

Actinomycetes have the genetic capability to synthesize many different biologically active secondary metabolites and of these compounds, antibiotics predominate in therapeutic and commercial importance. Intensive research often centres on the use of molecular techniques to investigate the physiology and genetics of antibiotic biosynthesis with a view to improving production. The isolation of clones of Streptomyces hygroscopicus, the producer of geldanamycin, which synthesizes geldanamycin in S. lividans, is reported. Molecular approaches using genes for elongation factors (tuf) were used in attempts to increase the fermentation yield of kirromycin, whilst probes for aphD and sph, genes for streptomycin phosphotransferases, were used to gather information on streptomycin genes in soil. Actinomycete populations in soil and earthworms may help in developing a strategy for discovering additional antimicrobials in soil. The relationship of proline metabolism to the secondary metabolite undecylprodigiosin and the carbon regulation of spiramycin biosynthesis in S. ambofaciens is also reported.

Actinomycetales↗