24 research outputs found
Discovery and Heterologous Production of New Cyclic Depsibosamycins
Streptomyces are producers of valuable secondary metabolites with unique scaffolds that
perform a plethora of biological functions. Nonribosomal peptides are of special interest due to their
variety and complexity. They are synthesized by nonribosomal peptide synthetases, large biosynthetic
machineries that are encoded in the genome of many Streptomyces species. The identification of
new peptides and the corresponding biosynthetic gene clusters is of major interest since knowledge
can be used to facilitate combinatorial biosynthesis and chemical semisynthesis of natural products.
The recently discovered bosamycins are linear octapeptides with an interesting 5-OMe tyrosine
moiety and various modifications at the N-terminus. In this study, the new cyclic depsibosamycins
B, C, and D from Streptomyces aurantiacus LU19075 were discovered. In comparison to the linear
bosamycins B, C, and D, which were also produced by the strain, the cyclic depsibosamycins showed
a side-chain-to-tail lactonization of serine and glycine, leading to a ring of four amino acids. In silico
identification and heterologous expression of the depsibosamycin (dbm) gene cluster indicated that
the cyclic peptides, rather than the linear derivatives, are the main products of the cluster
A Promiscuous Halogenase for the Derivatization of Flavonoids
Halogenation often improves the bioactive properties of natural products and is used
in pharmaceutical research for the generation of new potential drug leads. High regio- and stereospecificity, simple reaction conditions and straightforward downstream processing are the main
advantages of halogenation using enzymatic biocatalysts compared to chemical synthetic approaches.
The identification of new promiscuous halogenases for the modification of various natural products
is of great interest in modern drug discovery. In this paper, we report the identification of a new
promiscuous FAD-dependent halogenase, DklH, from Frankia alni ACN14a. The identified halogenase readily modifies various flavonoid compounds, including those with well-studied biological
activities. This halogenase has been demonstrated to modify not only flavones and isoflavones,
but also flavonols, flavanones and flavanonols. The structural requirements for DklH substrate
recognition were determined using a feeding approach. The homology model of DklH and the
mechanism of substrate recognition are also proposed in this paper
Cyclofaulknamycin with the Rare Amino Acid D-capreomycidine Isolated from a Well-Characterized Streptomyces albus Strain
Targeted genome mining is an efficient method of biosynthetic gene cluster prioritization
within constantly growing genome databases. Using two capreomycidine biosynthesis genes, alphaketoglutarate-dependent arginine beta-hydroxylase and pyridoxal-phosphate-dependent aminotransferase, we identified two types of clusters: one type containing both genes involved in the
biosynthesis of the abovementioned moiety, and other clusters including only arginine hydroxylase.
Detailed analysis of one of the clusters, the flk cluster from Streptomyces albus, led to the identification
of a cyclic peptide that contains a rare D-capreomycidine moiety for the first time. The absence
of the pyridoxal-phosphate-dependent aminotransferase gene in the flk cluster is compensated by
the XNR_1347 gene in the S. albus genome, whose product is responsible for biosynthesis of the
abovementioned nonproteinogenic amino acid. Herein, we report the structure of cyclofaulknamycin
and the characteristics of its biosynthetic gene cluster, biosynthesis and bioactivity profile
Flavacol and Its Novel Derivative 3-ÎČ-Hydroxy Flavacol from Streptomyces sp. Pv 4-95 after the Expression of Heterologous AdpA
Actinomycetes are one of the main producers of biologically active compounds. However,
their capabilities have not been fully evaluated due to the presence of many unexpressed silent
clusters; moreover, actinomycetes can probably produce new or previously discovered natural
products under certain conditions. Overexpressing the adpA gene into streptomycetes strains can
unlock silent biosynthetic gene clusters. Herein, we showed that by applying this approach to
Streptomyces sp. Pv 4-95 isolated from Phyllostachys viridiglaucescens rhizosphere soil, two new
mass peaks were identified. NMR structure analysis identified these compounds as flavacol and
a new 3-ÎČ-hydroxy flavacol derivative. We suggest that the presence of heterologous AdpA has
no direct effect on the synthesis of flavacol and its derivatives in the Pv 4-95 strain. However,
AdpA affects the synthesis of precursors by increasing their quantity, which then condenses into the
resulting compounds
Identification and Heterologous Expression of the Albucidin Gene Cluster from the Marine Strain Streptomyces Albus Subsp. Chlorinus NRRL B-24108
Herbicides with new modes of action and safer toxicological and environmental profiles are
needed to manage the evolution of weeds that are resistant to commercial herbicides. The unparalleled
structural diversity of natural products makes these compounds a promising source for new herbicides.
In 2009, a novel nucleoside phytotoxin, albucidin, with broad activity against grass and broadleaf
weeds was isolated from a strain of Streptomyces albus subsp. chlorinus NRRL B-24108. Here, we report
the identification and heterologous expression of the previously uncharacterized albucidin gene
cluster. Through a series of gene inactivation experiments, a minimal set of albucidin biosynthetic
genes was determined. Based on gene annotation and sequence homology, a model for albucidin
biosynthesis was suggested. The presented results enable the construction of producer strains for
a sustainable supply of albucidin for biological activity studies
Furaquinocins K and L : Novel Naphthoquinone-Based Meroterpenoids from Streptomyces sp. Je 1-369
Actinomycetes are the most prominent group of microorganisms that produce biologically
active compounds. Among them, special attention is focused on bacteria in the genus Streptomyces.
Streptomycetes are an important source of biologically active natural compounds that could be
considered therapeutic agents. In this study, we described the identification, purification, and
structure elucidation of two new naphthoquinone-based meroterpenoids, furaquinocins K and L,
from Streptomyces sp. Je 1-369 strain, which was isolated from the rhizosphere soil of Juniperus excelsa
(Bieb.). The main difference between furaquinocins K and L and the described furaquinocins was a
modification in the polyketide naphthoquinone skeleton. In addition, the structure of furaquinocin
L contained an acetylhydrazone fragment, which is quite rare for natural compounds. We also
identified a furaquinocin biosynthetic gene cluster in the Je 1-369 strain, which showed similarity
(60%) with the furaquinocin B biosynthetic gene cluster from Streptomyces sp. KO-3988. Furaquinocin
L showed activity against Gram-positive bacteria without cytotoxic effects
Bonsecamin: A New Cyclic Pentapeptide Discovered through Heterologous Expression of a Cryptic Gene Cluster
The intriguing structural complexity of molecules produced by natural organisms is
uncontested. Natural scaffolds serve as an important basis for the development of molecules with
broad applications, e.g., therapeutics or agrochemicals. Research in recent decades has demonstrated
that by means of classic metabolite extraction from microbes only a small portion of natural products
can be accessed. The use of genome mining and heterologous expression approaches represents a
promising way to discover new natural compounds. In this paper we report the discovery of a novel
cyclic pentapeptide called bonsecamin through the heterologous expression of a cryptic NRPS gene
cluster from Streptomyces albus ssp. chlorinus NRRL B-24108 in Streptomyces albus Del14. The new
compound was successfully isolated and structurally characterized using NMR. The minimal set of
genes required for bonsecamin production was determined through bioinformatic analysis and gene
deletion experiments. A biosynthetic route leading to the production of bonsecamin is proposed in
this paper
Dudomycins: New Secondary Metabolites Produced after Heterologous Expression of an Nrps Cluster from Streptomyces albus ssp. Chlorinus Nrrl B-24108
Since the 1950s, natural products of bacterial origin were systematically developed to
be used as drugs with a wide range of medical applications. The available treatment options
for many diseases are still not satisfying, wherefore, the discovery of new structures has not lost
any of its importance. Beyond the great variety of already isolated and characterized metabolites,
Streptomycetes still harbor uninvestigated gene clusters whose products can be accessed using
heterologous expression in host organisms. This works presents the discovery of a set of structurally
novel secondary metabolites, dudomycins A to D, through the expression of a cryptic NRPS cluster
from Streptomyces albus ssp. Chlorinus NRRL B-24108 in the heterologous host strain Streptomyces albus
Del14. A minimal set of genes, required for the production of dudomycins, was defined through gene
inactivation experiments. This paper also proposes a model for dudomycin biosynthesis
Targeted Dereplication of Microbial Natural Products by High-Resolution MS and Predicted LC Retention Time
A new strategy for the identification of known compounds in Streptomyces extracts that can be applied in the discovery of natural products is presented. The strategy incorporates screening a database of 5555 natural products including 5098 structures from Streptomyces sp., using a high-throughput LCMS data processing algorithm that utilizes HRMS data and predicted LC retention times (tR) as filters for rapid identification of known compounds in the natural product extract. The database, named StrepDB, contains for each compound the structure, molecular formula, molecular mass, and predicted LC retention time. All identified compounds are annotated and color coded for easier visualization. It is an indirect approach to quickly assess masses (which are not annotated) that may potentially lead to the discovery of new or novel structures. In addition, a spectral database named MbcDB was generated using the ACD/Spectrus DB Platform. MbcDB contains 665 natural products, each with structure, experimental HRESIMS, MS/MS, UV, and NMR spectra. StrepDB was used to screen a mutant Streptomyces albus extract, which led to the identification and isolation of two new compounds, legonmaleimides A and B, the structures of which were elucidated with the aid of MbcDB and spectroscopic techniques. The structures were confirmed by computer-assisted structure elucidation (CASE) methods using ACD/Structure Elucidator Suite. The developed methodology suggests a pipeline approach to the dereplication of extracts and discovery of novel natural products
Pseudochelin A, a siderophore of Pseudoalteromonas piscicida S2040
A new siderophore containing a 4,5-dihydroimidazole moiety was isolated from Pseudoalteromonas piscicida S2040 together with myxochelins A and B, alteramide A and its cycloaddition product, and bromo- and dibromoalterochromides. The structure of pseudochelin A was established by spectroscopic techniques including 2D NMR and MS/MS fragmentation data. In bioassays selected fractions of the crude extract of S2040 inhibited the opportunistic pathogen Pseudomonas aeruginosa. Pseudochelin A displayed siderophore activity in the chrome azurol S assay at concentrations higher than 50 ÎŒM, and showed weak activity against the fungus Aspergillus fumigatus, but did not display antibacterial, anti-inflammatory or anticonvulsant activity