| 28621949 |
Cyclotides from the Indian Medicinal Plant Viola odorata (Banafsha): Identification and Characterization |
10.1021/acs.jnatprod.6b01004. |
J Nat Prod |
Cyclotides from the Indian Medicinal Plant Viola odorata (Banafsha): Identification and Characterization
Abstract
- Cyclotides are cyclic cystine knotted macrocyclic plant peptides that have several promising applications. This study was undertaken to detect and identify known and new cyclotides in Viola odorata, a commercially important medicinal plant, from three geographical locations in India. The number of cyclotides in the plant varied with the tissue (leaves, petioles, flowers, runners, and roots) and with geographical locations in India. Using liquid chromatography coupled to Fourier transform mass spectrometry (FTMS), 166 cyclotide-like masses were observed to display cyclotide-diagnostic mass shifts following reduction, alkylation, and digestion, and 71 of these were positively identified based on automated spectrum matching. Of the remaining 95 putative cyclotides observed, de novo peptide sequencing of three new cyclotides, namely, vodo I1 (1), vodo I2 (2), and vodo I3 (3), was carried out with tandem mass spectrometry.
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| 28647504 |
Antimicrobial investigation of selected soil actinomycetes isolated from unexplored regions of Kashmir Himalayas, India |
10.1016/j.micpath.2017.06.017. |
Microb Pathog |
Antimicrobial investigation of selected soil actinomycetes isolated from unexplored regions of Kashmir Himalayas, India
Abstract
- The aim of the present study was to isolate and evaluate the antimicrobial potential of soil actinomycetes of Kashmir Himalayas. The secondary metabolites of actinomycetes are the prominent source of antibiotics. A total of 121 morphologically different actinomycete strains were isolated and screened for antimicrobial activity against various human pathogens. The ethyl acetate extract of fermented broth an actinomycete strain, identified as Streptomyces pratensis exhibited significant antimicrobial activity against Staphylococcus aureus ATCC 29213 with MIC 0.25 μg/ml and Mycobacterium tuberculosis Strain H37Rv with MIC 0.062 μg/ml. The strain S. pratensis IIIM06 was grown on large scale and their broth was extracted with ethyl acetate. The extract was subjected to various chromatography techniques which led to the isolation of four compounds whose structures were established as actinomycin C1, actinomycin C2, actinomycin C3 and actiphenol on the basis of spectral data analysis. Actinomycin C1, C2 and C3 exhibited potent antimicrobial activity against S. aureus as well as M. tuberculosis. The isolated indigenous actinomycetes exhibited good antibacterial activity and the study reveals that IIIM06 is a promising strain and could be of great potential for industrial applications.
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| 28650559 |
The antibacterial activity and modes of LI-F type antimicrobial peptides against Bacillus cereus in vitro |
10.1111/jam.13526. |
J Appl Microbiol |
The antibacterial activity and modes of LI-F type antimicrobial peptides against Bacillus cereus in vitro
Abstract
- LI-Fs are a family of highly potent cyclic lipodepsipeptide antibiotics with a broad antimicrobial spectrum (Gram-positive bacteria and fungi). In this study, LI-F-type antimicrobial peptides (AMP-jsa9) composing of LI-F03a, LI-F03b, LI-F04a, LI-F04b and LI-F05b were isolated from Paenibacillus polymyxa JSA-9. To better understand the antimicrobial mechanism of AMP-jsa9, the potency and action(s) of AMP-jsa9 against Bacillus cereus were examined.
Flow cytometry, confocal laser microscopy, scanning electron microscopy, transmission electron microscopy (TEM) and atomic force microscopy observation, as well as determination of peptidoglycan and cell wall-associated protein and other methods were used. The results indicate that AMP-jsa9 exhibits strong, broad-spectrum antimicrobial activity. Moreover, AMP-jsa9 targets the cell wall and membrane of B. cereus to impair membrane integrity, increase membrane permeability and enhance cytoplasm leakage (e.g. K , protein, nucleic acid). This leads to bacterial cells with irregular, withered and coarse surfaces. In addition, AMP-jsa9 is also able to bind to DNA and break down B. cereus biofilms.
In this study, the action mechanism of LI-Fs against B. cereus was clarified in details.
The results of this study provide a theoretical basis for utilizing AMP-jsa9 or similar analogues as natural and effective preservatives in the food and feed industries. These efforts could also stimulate research activities interested in understanding the specific effects of other antimicrobial agents.
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| 28665343 |
Tricholides A and B and Unnarmicin D: New Hybrid PKS-NRPS Macrocycles Isolated from an Environmental Collection of Trichodesmium thiebautii |
10.3390/md15070206. |
Mar Drugs |
Tricholides A and B and Unnarmicin D: New Hybrid PKS-NRPS Macrocycles Isolated from an Environmental Collection of Trichodesmium thiebautii
Abstract
- Bioassay-guided isolation of the lipophilic extract of bloom material led to the purification and structure characterization of two new hybrid polyketide-non-ribosomal peptide (PKS-NRPS) macrocyclic compounds, tricholides A and B ( and ). A third macrocyclic compound, unnarmicin D (), was identified as a new depsipeptide in the unnarmicin family, given its structural similarity to the existing compounds in this group. The planar structures of - were determined using 1D and 2D NMR spectra and complementary spectroscopic and spectrometric procedures. The absolute configurations of the amino acid components of - were determined via acid hydrolysis, derivitization with Marfey's reagent and HPLC-UV comparison to authentic amino acid standards. The absolute configuration of the 3-hydroxydodecanoic acid moiety in was determined using a modified Mosher's esterification procedure on a linear derivative of tricharmicin () and additionally by a comparison of C NMR shifts of to known depsipeptides with -hydroxy acid subunits. Tricholide B () showed moderate cytotoxicity to Neuro-2A murine neuroblastoma cells (EC: 14.5 ± 6.2 μM).
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| 28667013 |
Cross-linking of dicyclotyrosine by the cytochrome P450 enzyme CYP121 from proceeds through a catalytic shunt pathway |
10.1074/jbc.M117.794099. |
J Biol Chem |
Cross-linking of dicyclotyrosine by the cytochrome P450 enzyme CYP121 from proceeds through a catalytic shunt pathway
Abstract
- CYP121, the cytochrome P450 enzyme in that catalyzes a single intramolecular C-C cross-linking reaction in the biosynthesis of mycocyclosin, is crucial for the viability of this pathogen. This C-C coupling reaction represents an expansion of the activities carried out by P450 enzymes distinct from oxygen insertion. Although the traditional mechanism for P450 enzymes has been well studied, it is unclear whether CYP121 follows the general P450 mechanism or uses a different catalytic strategy for generating an iron-bound oxidant. To gain mechanistic insight into the CYP121-catalyzed reaction, we tested the peroxide shunt pathway by using rapid kinetic techniques to monitor the enzyme activity with its substrate dicyclotyrosine (cYY) and observed the formation of the cross-linked product mycocyclosin by LC-MS. In stopped-flow experiments, we observed that cYY binding to CYP121 proceeds in a two-step process, and EPR spectroscopy indicates that the binding induces active site reorganization and uniformity. Using rapid freeze-quenching EPR, we observed the formation of a high-spin intermediate upon the addition of peracetic acid to the enzyme-substrate complex. This intermediate exhibits a high-spin ( = 5/2) signal with g values of 2.00, 5.77, and 6.87. Likewise, iodosylbenzene could also produce mycocyclosin, implicating compound I as the initial oxidizing species. Moreover, we also demonstrated that CYP121 performs a standard peroxidase type of reaction by observing substrate-based radicals. On the basis of these results, we propose plausible free radical-based mechanisms for the C-C bond coupling reaction.
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| 28705677 |
Hyicin 4244, the first sactibiotic described in staphylococci, exhibits an anti-staphylococcal biofilm activity |
10.1016/j.ijantimicag.2017.06.025. |
Int J Antimicrob Agents |
Hyicin 4244, the first sactibiotic described in staphylococci, exhibits an anti-staphylococcal biofilm activity
Abstract
- Hyicin 4244 is a small antimicrobial peptide with a broad spectrum of activity that was found in the culture supernatant of Staphylococcus hyicus 4244, the genome of which was then sequenced. The bacteriocin gene cluster (hyiSABCDEFG) was mined from its single chromosome and exhibited a genetic organization similar to that of subtilosin A. All genes involved in hyicin 4244 biosynthesis proved to be transcribed and encode proteins that share at least 42% similarity to proteins encoded by the subtilosin A gene cluster. Due to its resemblance to subtilosin A and the presence of three thioether bonds in its structure, hyicin 4244 is assumed to be a 35-amino acid circular sactibiotic, the first to be described in staphylococci. Hyicin 4244 inhibited 14 staphylococcal isolates from either human infections or bovine mastitis, all biofilm formers. Hyicin 4244 significantly reduced the number of colony-forming units (CFU) and the biofilm formation by two strong biofilm-forming strains randomly chosen as representatives of the strains involved in human infections and bovine mastitis. It also reduced the proliferation and viability of sessile cells in established biofilms. Therefore, hyicin 4244 proved not only to prevent biofilm formation by planktonic cells, but also to penetrate the biofilm matrix in vitro, exerting bactericidal activity against staphylococcal sessile cells. This bacteriocin has the potential to become an alternative antimicrobial for either prevention or treatment of biofilm-related infections caused by different staphylococcal species.
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| 28709434 |
Integrating multi-omics analyses of Nonomuraea dietziae to reveal the role of soybean oil in [(4'-OH)MeLeu]-CsA overproduction |
10.1186/s12934-017-0739-0. |
Microb Cell Fact |
Integrating multi-omics analyses of Nonomuraea dietziae to reveal the role of soybean oil in [(4'-OH)MeLeu]-CsA overproduction
Abstract
- Nonomuraea dietziae is a promising microorganism to mediate the region-specific monooxygenation reaction of cyclosporine A (CsA). The main product [(4'-OH)MeLeu]-CsA possesses high anti-HIV/HCV and hair growth-stimulating activities while avoiding the immunosuppressive effect of CsA. However, the low conversion efficiency restricts the clinical application. In this study, the production of [(4'-OH)MeLeu]-CsA was greatly improved by 55.6% from 182.8 to 284.4 mg/L when supplementing soybean oil into the production medium, which represented the highest production of [(4'-OH)MeLeu]-CsA so far.
To investigate the effect of soybean oil on CsA conversion, some other plant oils (corn oil and peanut oil) and the major hydrolysates of soybean oil were fed into the production medium, respectively. The results demonstrated that the plant oils, rather than the hydrolysates, could significantly improve the [(4'-OH)MeLeu]-CsA production, suggesting that soybean oil might not play its role in the lipid metabolic pathway. To further unveil the mechanism of [(4'-OH)MeLeu]-CsA overproduction under the soybean oil condition, a proteomic analysis based on the two-dimensional gel electrophoresis coupled with MALDI TOF/TOF mass spectrometry was implemented. The results showed that central carbon metabolism, genetic information processing and energy metabolism were significantly up-regulated under the soybean oil condition. Moreover, the gas chromatography-mass spectrometry-based metabolomic analysis indicated that soybean oil had a great effect on amino acid metabolism and tricarboxylic acid cycle. In addition, the transcription levels of cytochrome P450 hydroxylase (CYP) genes for CsA conversion were determined by RT-qPCR and the results showed that most of the CYP genes were up-regulated under the soybean oil condition.
These findings indicate that soybean oil could strengthen the primary metabolism and the CYP system to enhance the mycelium growth and the monooxygenation reaction, respectively, and it will be a guidance for the further metabolic engineering of this strain.
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| 28715095 |
A Self-Sacrificing N-Methyltransferase Is the Precursor of the Fungal Natural Product Omphalotin |
10.1002/anie.201703488. |
Angew Chem Int Ed Engl |
A Self-Sacrificing N-Methyltransferase Is the Precursor of the Fungal Natural Product Omphalotin
Abstract
- Research on ribosomally synthesized and posttranslationally modified peptides (RiPPs) has led to an increasing understanding of biosynthetic mechanisms, mostly drawn from bacterial examples. In contrast, reports on RiPPs from fungal producers, apart from the amanitins and phalloidins, are still scarce. The fungal cyclopeptide omphalotin A carries multiple N-methylations on the peptide backbone, a modification previously known only from nonribosomal peptides. Mining the genome of the omphalotin-producing fungus for a precursor peptide led to the identification of two biosynthesis genes, one encoding a methyltransferase OphMA that catalyzes the automethylation of its C-terminus, which is then released and cyclized by the protease OphP. Our findings suggest a novel biosynthesis mechanism for a RiPP in which a modifying enzyme bears its own precursor peptide.
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| 28741926 |
Redesigned Spider Peptide with Improved Antimicrobial and Anticancer Properties |
10.1021/acschembio.7b00459. |
ACS Chem Biol |
Redesigned Spider Peptide with Improved Antimicrobial and Anticancer Properties
Abstract
- Gomesin, a disulfide-rich antimicrobial peptide produced by the Brazilian spider Acanthoscurria gomesiana, has been shown to be potent against Gram-negative bacteria and to possess selective anticancer properties against melanoma cells. In a recent study, a backbone cyclized analogue of gomesin was shown to be as active but more stable than its native form. In the current study, we were interested in improving the antimicrobial properties of the cyclic gomesin, understanding its selectivity toward melanoma cells and elucidating its antimicrobial and anticancer mode of action. Rationally designed analogues of cyclic gomesin were examined for their antimicrobial potency, selectivity toward cancer cells, membrane-binding affinity, and ability to disrupt cell and model membranes. We improved the activity of cyclic gomesin by ∼10-fold against tested Gram-negative and Gram-positive bacteria without increasing toxicity to human red blood cells. In addition, we showed that gomesin and its analogues are more toxic toward melanoma and leukemia cells than toward red blood cells and act by selectively targeting and disrupting cancer cell membranes. Preference toward some cancer types is likely dependent on their different cell membrane properties. Our findings highlight the potential of peptides as antimicrobial and anticancer leads and the importance of selectively targeting cancer cell membranes for drug development.
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| 28771849 |
In vivo Evaluation of an Engineered Cyclotide as Specific CXCR4 Imaging Reagent |
10.1002/chem.201702540. |
Chemistry |
In vivo Evaluation of an Engineered Cyclotide as Specific CXCR4 Imaging Reagent
Abstract
- The CXCR4 chemokine receptor plays a key regulatory role in many biological functions, including embryonic development and controlling leukocyte functions during inflammation and immunity. CXCR4 has been also associated with multiple types of cancers where its overexpression/activation promotes metastasis, angiogenesis, and tumor growth and/or survival. Furthermore, CXCR4 is involved in HIV replication, as it is a co-receptor for viral entry into host cells. Altogether, these features make CXCR4 a very attractive target for the development of imaging and therapeutic agents. Here, the in vivo evaluation of the MCoTI-based cyclotide, MCo-CVX-5c, for the development of imaging agents that target CXCR4 is reported. Cyclotide MCo-CVX-5c is a potent CXCR4 antagonist with a remarkable in vivo resistance to biological degradation in serum. A [ Cu]-DOTA-labeled version of this cyclotide demonstrated high and significant uptake in U87-stb-CXCR4 tumors compared to the control U87 tumors. Furthermore, protracted imaging studies demonstrated radiotracer retention in the U87-stb-CXCR4 tumor at 24 h post injection. Uptake in U87-stb-CXCR4 tumors could be blocked by unlabeled MCo-CVX-5c, showing high in vivo specificity. These results demonstrate the in vivo specificity and retention of a bioactive molecularly targeted cyclotide and highlight the potential of bioactive cyclotides for the development of new imaging agents that target CXCR4.
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| 28833783 |
Intramolecular cyclization of the antimicrobial peptide Polybia-MPI with triazole stapling: influence on stability and bioactivity |
10.1002/psc.3031. |
J Pept Sci |
Intramolecular cyclization of the antimicrobial peptide Polybia-MPI with triazole stapling: influence on stability and bioactivity
Abstract
- Cationic antimicrobial peptides have attracted increasing attention as a novel class of antibiotics to treat infectious diseases caused by pathogenic bacteria. However, susceptibility to protease is a shortcoming in their development. Cyclization is one approach to increase the proteolytic resistance of peptides. Therefore, to improve the proteolytic resistance of Polybia-MPI, we have synthesized the MPI cyclic analogs C-MPI-1 (i-to-i+4) and C-MPI-2 (i-to-i+6) by copper(I)-catalyzed azide-alkyne cycloaddition. Compared with MPI, C-MPI-1 displayed sustained antimicrobial activity and had enhanced anti-trypsin resistance, while C-MPI-2 displayed no antimicrobial activity. The relationship between peptide structure and bioactivity was further investigated by probing the secondary structure of the peptides by circular dichroism. This showed that C-MPI-1 adopted an α-helical structure in aqueous solution and, interestingly, had increased α-helical conformation in 30 mM sodium dodecyl sulfate and 50% trifluoroethyl alcohol compared with MPI. C-MPI-2 that was not α-helical in structure, suggesting that the propensity for α-helix conformation may play an important role in cyclic peptide design. In addition, scanning electron microscopy, propidium iodide uptake, and membrane permeabilization assays indicated that MPI and the optimized analog C-MPI-1 had membrane-active action modes, indicating that the peptides would not be susceptible to conventional resistance mechanisms. Our study provides additional insight into the influence of intramolecular cyclization at various positions on peptide structure and biological activity. In conclusion, the design and synthesis of cyclic analogs via click chemistry offer a new strategy for the development of stable antimicrobial agents. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.
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| 28841315 |
Thermoactinoamide A, an Antibiotic Lipophilic Cyclopeptide from the Icelandic Thermophilic Bacterium Thermoactinomyces vulgaris |
10.1021/acs.jnatprod.7b00560. |
J Nat Prod |
Thermoactinoamide A, an Antibiotic Lipophilic Cyclopeptide from the Icelandic Thermophilic Bacterium Thermoactinomyces vulgaris
Abstract
- The thermophilic bacterium Thermoactinomyces vulgaris strain ISCAR 2354, isolated from a coastal hydrothermal vent in Iceland, was shown to contain thermoactinoamide A (1), a new cyclic hexapeptide composed of mixed d and l amino acids, along with five minor analogues (2-6). The structure of 1 was determined by one- and two-dimensional NMR spectroscopy, high-resolution tandem mass spectrometry, and advanced Marfey's analysis of 1 and of the products of its partial hydrolysis. Thermoactinoamide A inhibited the growth of Staphylococcus aureus ATCC 6538 with an MIC value of 35 μM. On the basis of literature data and this work, cyclic hexapeptides with mixed d/l configurations, one aromatic amino acid residue, and a prevalence of lipophilic residues can be seen as a starting point to define a new, easily accessible scaffold in the search for new antibiotic agents.
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| 28846366 |
Structure, Biosynthesis, and Biological Activity of the Cyclic Lipopeptide Anikasin |
10.1021/acschembio.7b00589. |
ACS Chem Biol |
Structure, Biosynthesis, and Biological Activity of the Cyclic Lipopeptide Anikasin
Abstract
- The class of cyclic lipopeptide natural products consists of compounds with a diverse range of bioactivities. In this study, we elucidated the structure of the cyclic lipopeptide anikasin using X-ray crystallography, analyzed its biosynthetic gene cluster, and investigated its natural role in the interaction between the producer strain Pseudomonas fluorescens HKI0770 and protozoal predators. These results led to the conclusion that anikasin has dual functionality enabling swarming motility and acting as a niche amoebicide, which effectively inhibits the social amoeba Polysphondylium violaceum and protects the producer strain from protozoal grazing.
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| 28851841 |
Backbone cyclization of analgesic conotoxin GeXIVA facilitates direct folding of the ribbon isomer |
10.1074/jbc.M117.808386. |
J Biol Chem |
Backbone cyclization of analgesic conotoxin GeXIVA facilitates direct folding of the ribbon isomer
Abstract
- Conotoxin GeXIVA inhibits the α9α10 nicotinic acetylcholine receptor (nAChR) and is analgesic in animal models of pain. α-Conotoxins have four cysteines that can have three possible disulfide connectivities: globular (Cys-Cys and Cys-Cys), ribbon (Cys-Cys and Cys-Cys), or bead (Cys-Cys and Cys-Cys). Native α-conotoxins preferably adopt the globular connectivity, and previous studies of α-conotoxins have focused on the globular isomers as the ribbon and bead isomers typically have lower potency at nAChRs than the globular form. A recent report showed that the bead and ribbon isomers of GeXIVA are more potent than the globular isomer, with low nanomolar half-maximal inhibitory concentrations (IC). Despite this high potency, the therapeutic potential of GeXIVA is limited, because like most peptides, it is susceptible to proteolytic degradation and is challenging to synthesize in high yield. Here we used backbone cyclization as a strategy to improve the folding yield as well as increase the serum stability of ribbon GeXIVA while preserving activity at the α9α10 nAChR. Specifically, cyclization of ribbon GeXIVA with a two-residue linker maintained the biological activity at the human α9α10 nAChR and improved stability in human serum. Short linkers led to selective formation of the ribbon disulfide isomer without requiring orthogonal protection. Overall, this study highlights the value of backbone cyclization in directing folding, improving yields, and stabilizing conotoxins with therapeutic potential.
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| 28876933 |
Namalides B and C and Spumigins K-N from the Cultured Freshwater Cyanobacterium Sphaerospermopsis torques-reginae |
10.1021/acs.jnatprod.7b00370. |
J Nat Prod |
Namalides B and C and Spumigins K-N from the Cultured Freshwater Cyanobacterium Sphaerospermopsis torques-reginae
Abstract
- Chemical investigations of the terrestrial cyanobacterium Sphaerospermopsis torques-reginae ITEP-024 from northern Brazil afforded namalides B (1) and C (2), the first analogues of this anabaenopeptide-like metabolite to be described. Four other related peptides (3-6), termed spumigins K-N, were also identified. Planar structures and absolute configurations for 1, 2, and 3a-6a were deduced by a combination of 2D NMR, HRMS analysis, and Marfey's methodology. Spumigins K-N (3-6) are the first examples of spumigins containing a 2-hydroxy-4-(4-hydroxyphenyl)butanoic acid (Hhpba) in the N-terminal position. Compounds 1 and 2 inhibited carboxypeptidase A with IC values of 0.75 and 2.0 μM, respectively.
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