The extract of UIC 10035, a strain obtained from a sample collected near the town of Homestead, South Florida, showed antiproliferative activity against MDA-MB-435 cells. Bioassay-guided fractionation led to the isolation of a series of cyclic lipodecapeptides, named minutissamides E-L (1-8). The planar structures were determined by analysis of HRESIMS, tandem MS, and 1D and 2D NMR data, and the stereoconfigurations were assigned by LC-MS analysis of the Marfey's derivatives after acid hydrolysis. Minutissamides E-L (1-8) exhibited antiproliferative activity against MDA-MB-435 cells with IC(50) values ranging between 1 and 10μM. The structures of minutissamides E-L (1-8) were closely related with those of the previously reported lipopeptides, puwainaphycins A-E and minutissamides A-D, characterized by the presence of a lipophilic β-amino acid and three non-standard amino acids NMeAsn, OMeThr and Dhb (α,β-dehydro-α-aminobutyric acid). The strain UIC 10035 was designated as cf. Anabaena sp. on the basis of morphological and 16S rRNA gene sequence analyses.
[Show abstract][Hide abstract] ABSTRACT: Two new cyclic lipopeptides, trichormamides A (1) and B (2), were isolated from the cultured freshwater cyanobacterium Trichormus sp. UIC 10339. The strain was obtained from a sample collected in Raven Lake in Northern Wisconsin. The planar structures of trichormamides A (1) and B (2) were determined using a combination of spectroscopic analyses including HRESIMS and 1D and 2D NMR experiments. The absolute configurations of the amino acid residues were assigned by the advanced Marfey's method after acid hydrolysis. Trichormamide A (1) is a cyclic undecapeptide containing two d-amino acid residues (d-Tyr and d-Leu) and one β-amino acid residue (β-aminodecanoic acid). Trichormamide B (2) is a cyclic dodecapeptide characterized by the presence of four nonstandard α-amino acid residues (homoserine, N-methylisoleucine, and two 3-hydroxyleucines) and one β-amino acid residue (β-aminodecanoic acid). Trichormamide B (2) was cytotoxic against MDA-MB-435 and HT-29 cancer cell lines with IC50 values of 0.8 and 1.5 μM, respectively.
[Show abstract][Hide abstract] ABSTRACT: A putative operon encoding the biosynthetic pathway for the cytotoxic cyanobacterial lipopeptides puwainphycins was identified in Cylindrospermum alatosporum. Bioinformatics analysis enabled sequential prediction of puwainaphycin biosynthesis; this process is initiated by the activation of a fatty acid residue via fatty acyl-AMP ligase and continued by a multidomain non-ribosomal peptide synthetase/polyketide synthetase. High-resolution mass spectrometry and nuclear magnetic resonance spectroscopy measurements proved the production of puwainaphycin F/G congeners differing in FA chain length formed by either 3-amino-2-hydroxy-4-methyl dodecanoic acid (4-methyl-Ahdoa) or 3-amino-2-hydroxy-4-methyl tetradecanoic acid (4-methyl-Ahtea). Because only one puwainaphycin operon was recovered in the genome, we suggest that the fatty acyl-AMP ligase and one of the amino acid adenylation domains (Asn/Gln) show extended substrate specificity. Our results provide the first insight into the biosynthesis of frequently occurring β-amino fatty acid lipopeptides in cyanobacteria, which may facilitate analytical assessment and development of monitoring tools for cytotoxic cyanobacterial lipopeptides.
PLoS ONE 11/2014; 9(11):e111904. DOI:10.1371/journal.pone.0111904 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: There is mounting evidence that cyanobacterial lipopeptides can kill mammalian cells presenting a hazard to human health. Unfortunately, their toxicity mechanism is poorly understood. We have isolated new cyclic undeca-lipopeptides muscotoxin A and B containing unique lipophilic residue 3-amino-2,5-dihydroxydecanoic acid (5-OH Ahdoa). Muscotoxin B was not used for biological studies due to its poor yield. Muscotoxin A was cytotoxic to YAC-1, Sp/2 and HeLa cancer cell lines (LC50 ranged from 9.9 μM to 13.2 μM in 24h exposure) causing membrane damage and influx of calcium ions. Subsequently, we studied this lytic mechanism using synthetic liposomes embedded with fluorescent probes. Muscotoxin A permeabilised liposomes composed exclusively of phospholipids demonstrating no proteins or carbohydrates present in biomembranes are essential for its activity. Paradoxically, permeabilisation activity of muscotoxin A was mediated by significant reduction of membrane surface fluidity (stiffening), the opposite of synthetic detergents and cytolytic lipopeptide puwainaphycin F. At 25°C, muscotoxin A disrupted liposomes with and without cholesterol/sphingomyelin, however, at 37°C it was selective against liposomes with cholesterol/sfingomyelin. It appears that both membrane fluidity and organisation can affect lytic activity of muscotoxin A. Our findings strengthen the evidence that cyanobacterial lipopeptides disrupt specifically mammalian cell membranes and bring new insights into the mechanism of this effect.μ
Chemical Research in Toxicology 01/2015; 28(2). DOI:10.1021/tx500382b · 3.53 Impact Factor
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