| 23442790 |
Thalassospiramide G, a new γ-amino-acid-bearing peptide from the marine bacterium Thalassospira sp |
10.3390/md11030611. |
Mar Drugs |
Thalassospiramide G, a new γ-amino-acid-bearing peptide from the marine bacterium Thalassospira sp
Abstract
- In the chemical investigation of marine unicellular bacteria, a new peptide, thalassospiramide G (1), along with thalassospiramides A and D (2-3), was discovered from a large culture of Thalassospira sp. The structure of thalassospiramide G, bearing γ-amino acids, such as 4-amino-5-hydroxy-penta-2-enoic acid (AHPEA), 4-amino-3,5-dihydroxy-pentanoic acid (ADPA), and unique 2-amino-1-(1H-indol-3-yl) etha (AIEN), was determined via extensive spectroscopic analysis. The absolute configuration of thalassospiramide D (3), including 4-amino-3-hydroxy-5-phenylpentanoic acid (AHPPA), was rigorously determined by 1H-1H coupling constant analysis and chemical derivatization. Thalassospiramides A and D (2-3) inhibited nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated mouse macrophage RAW 264.7 cells, with IC(50) values of 16.4 and 4.8 μM, respectively.
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| 23490156 |
The three-dimensional solution structure of mini-M conotoxin BtIIIA reveals a disconnection between disulfide connectivity and peptide fold |
10.1016/j.bmc.2013.02.012. |
Bioorg Med Chem |
The three-dimensional solution structure of mini-M conotoxin BtIIIA reveals a disconnection between disulfide connectivity and peptide fold
Abstract
- Conotoxins are bioactive peptides from the venoms of marine snails and have been divided into several superfamilies based on homologies in their precursor sequences. The M-superfamily conotoxins can be further divided into five branches based on the number of residues in the third loop of the peptide sequence. Recently two M-1 branch conotoxins (tx3a and mr3e) with a C1-C5, C2-C4, C3-C6 disulfide connectivity and one M-2 branch conotoxin (mr3a) with a C1-C6, C2-C4, C3-C5 disulfide connectivity were described. Here we report the disulfide connectivity, chemical synthesis and the three-dimensional NMR structure of the novel 14-residue conotoxin BtIIIA, extracted from the venom of Conus betulinus. It has the same disulfide connectivity as mr3a, which puts it in the M-2 branch conotoxins but has a distinctly different structure from other M-2 branch conotoxins. 105 NOE distance restraints and seven dihedral angle restraints were used for the structure calculations. The three-dimensional structure was determined with CYANA based on torsion angle dynamics and refinement in a water solvent box was carried out with CNS. Fifty structures were calculated and the 20 lowest energy structures superimposed with a RMSD of 0.49±0.16 Å. Even though it has the M-2 branch disulfide connectivity, BtIIIA was found to have a 'flying bird' backbone motif depiction that is found in the M-1 branch conotoxin mr3e. This study shows that conotoxins with the same cysteine framework can have different disulfide connectivities and different peptide folds.
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| 23557677 |
Mammalian neuronal sodium channel blocker μ-conotoxin BuIIIB has a structured N-terminus that influences potency |
10.1021/cb300674x. |
ACS Chem Biol |
Mammalian neuronal sodium channel blocker μ-conotoxin BuIIIB has a structured N-terminus that influences potency
Abstract
- Among the μ-conotoxins that block vertebrate voltage-gated sodium channels (VGSCs), some have been shown to be potent analgesics following systemic administration in mice. We have determined the solution structure of a new representative of this family, μ-BuIIIB, and established its disulfide connectivities by direct mass spectrometric collision induced dissociation fragmentation of the peptide with disulfides intact. The major oxidative folding product adopts a 1-4/2-5/3-6 pattern with the following disulfide bridges: Cys5-Cys17, Cys6-Cys23, and Cys13-Cys24. The solution structure reveals that the unique N-terminal extension in μ-BuIIIB, which is also present in μ-BuIIIA and μ-BuIIIC but absent in other μ-conotoxins, forms part of a short α-helix encompassing Glu3 to Asn8. This helix is packed against the rest of the toxin and stabilized by the Cys5-Cys17 and Cys6-Cys23 disulfide bonds. As such, the side chain of Val1 is located close to the aromatic rings of Trp16 and His20, which are located on the canonical helix that displays several residues found to be essential for VGSC blockade in related μ-conotoxins. Mutations of residues 2 and 3 in the N-terminal extension enhanced the potency of μ-BuIIIB for NaV1.3. One analogue, [d-Ala2]BuIIIB, showed a 40-fold increase, making it the most potent peptide blocker of this channel characterized to date and thus a useful new tool with which to characterize this channel. On the basis of previous results for related μ-conotoxins, the dramatic effects of mutations at the N-terminus were unanticipated and suggest that further gains in potency might be achieved by additional modifications of this region.
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| 23566170 |
Metabolites from carnivorous fungus Arthrobotrys entomopaga and their functional roles in fungal predatory ability |
10.1021/jf400615h. |
J Agric Food Chem |
Metabolites from carnivorous fungus Arthrobotrys entomopaga and their functional roles in fungal predatory ability
Abstract
- The carnivorous fungus Arthrobotrys entomopaga (Drechsler) can develop adhesive knobs to capture nematodes. Chemical study on the culture medium of A. entomopaga producing adhesive knobs led to isolation of six trace amounts of metabolites, including two new metabolites, paganins A and B (1 and 2), blumenol A (3), talathermophilins A and B (4 and 5), and cyclo(glycyltryptophyl) (6). Compounds 3-6 were reported for the first time from carnivorous fungi. Compounds 1 and 2 promoted the formation of the predatory adhesive knobs with an increasing rate up to 118% at a concentration of 50 μM but showed moderate inhibitory activity at a concentration of 5 μM. Moreover, compounds 1 and 2 displayed strong inhibitory activities toward the formation of A. entomopaga conidiophores with inhibitory rates of 40-75%. Growth experiments suggested that compounds 1 and 2 could be involved in the regulation of the fungal predatory and reproductive abilities. Nematode chemotaxis bioassay indicated that compounds 1 and 3 displayed strong nematode-attracting abilities. These findings provided a new type of regulatory metabolite and support for the hypothesis that predators often evolve to respond to their metazoan prey.
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| 23566299 |
Determination of the α-conotoxin Vc1.1 binding site on the α9α10 nicotinic acetylcholine receptor |
10.1021/jm400041h. |
J Med Chem |
Determination of the α-conotoxin Vc1.1 binding site on the α9α10 nicotinic acetylcholine receptor
Abstract
- α-Conotoxin Vc1.1 specifically and potently inhibits the nicotinic acetylcholine receptor subtype α9α10 (α9α10 nAChR) and is a potential novel treatment for neuropathic pain. Here, we used a combination of computational modeling and electrophysiology experiments to determine the Vc1.1 binding site on the α9α10 nAChR. Interactions of Vc1.1 with two probable binding sites, α9α10 and α10α9, were modeled. Mutational energies calculated by assuming specific interactions in the α10α9 binding site correlated better with electrophysiological recordings than those assuming interactions with the α9α10 binding site. Two novel Vc1.1 analogues, [N9F]Vc1.1 and [N9W]Vc1.1, were predicted to have large differences in affinity between the two binding sites. Data from functional studies were consistent with computational predictions that assumed preferred binding of Vc1.1 to the α10α9 pocket. Moreover, our modeling study suggested that a single hydrogen bond formed between Vc1.1 and position 59 of the α10α9 pocket confers specificity to rat versus human α9α10 nAChRs.
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| 23567999 |
Identification, structural and pharmacological characterization of τ-CnVA, a conopeptide that selectively interacts with somatostatin sst3 receptor |
10.1016/j.bcp.2013.03.019. |
Biochem Pharmacol |
Identification, structural and pharmacological characterization of τ-CnVA, a conopeptide that selectively interacts with somatostatin sst3 receptor
Abstract
- Conopeptides are a diverse array of small linear and reticulated peptides that interact with high potency and selectivity with a large diversity of receptors and ion channels. They are used by cone snails for prey capture or defense. Recent advances in venom gland transcriptomic and venom peptidomic/proteomic technologies combined with bioactivity screening approaches lead to the identification of new toxins with original pharmacological profiles. Here, from transcriptomic/proteomic analyses of the Conus consors cone snail, we identified a new conopeptide called τ-CnVA, which displays the typical cysteine framework V of the T1-conotoxin superfamily. This peptide was chemically synthesized and its three-dimensional structure was solved by NMR analysis and compared to that of TxVA belonging to the same family, revealing very few common structural features apart a common orientation of the intercysteine loop. Because of the lack of a clear biological function associated with the T-conotoxin family, τ-CnVA was screened against more than fifty different ion channels and receptors, highlighting its capacity to interact selectively with the somatostatine sst3 receptor. Pharmacological and functional studies show that τ-CnVA displays a micromolar (Ki of 1.5μM) antagonist property for the sst3 receptor, being currently the only known toxin to interact with this GPCR subfamily.
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| 23586970 |
Nocardiamides A and B, two cyclohexapeptides from the marine-derived actinomycete Nocardiopsis sp. CNX037 |
10.1021/np400009a. |
J Nat Prod |
Nocardiamides A and B, two cyclohexapeptides from the marine-derived actinomycete Nocardiopsis sp. CNX037
Abstract
- Two new cyclic hexapeptides, nocardiamides A (1) and B (2), were isolated from the culture broth of marine-derived actinomycete CNX037 strain that was identified as a Nocardiopsis species. The planar structures of nocardiamides A (1) and B (2) were assigned on the basis of 1D and 2D NMR and HRESIMS spectroscopic analyses. Their absolute configurations were deduced by the advanced Marfey's method and chiral-phase HPLC analysis. The challenge of locating two d- and one l-valine residue in 1 and 2 was accomplished by total synthesis using solid-phase peptide synthetic methods. Both 1 and 2 showed negligible antimicrobial activities against seven indicator strains and exhibited no cytotoxicity against HCT-116.
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| 23600807 |
Secondary metabolites from the endophytic fungi Penicillium polonicum and Aspergillus fumigatus |
10.1080/10286020.2013.780349. |
J Asian Nat Prod Res |
Secondary metabolites from the endophytic fungi Penicillium polonicum and Aspergillus fumigatus
Abstract
- Two new compounds, rhodostegone (1) from endophytic fungus Penicillium polonicum and cyclo-(l-Val-l-Leu) (2) from Aspergillus fumigatus, together with six known diketopiperazines (3-8), were isolated. The structures of these compounds were characterized through a combination of extensive IR, MS, NMR, and CD analysis.
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| 23607568 |
Total synthesis of the marine cyclic depsipeptide viequeamide a |
10.1021/np4001027. |
J Nat Prod |
Total synthesis of the marine cyclic depsipeptide viequeamide a
Abstract
- The first total synthesis of viequeamide A, a natural cyclic depsipeptide isolated from a marine button cyanobacterium, was achieved with the N-Me-Val-Thr peptide bond as the final macrocyclization site. The synthetic product gave nearly identical spectroscopic data to that reported for the natural product.
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| 23609992 |
Total synthesis of the antifungal agent echinocandin C |
10.1002/anie.201301262. |
Angew Chem Int Ed Engl |
Total synthesis of the antifungal agent echinocandin C
Abstract
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| 23620594 |
Substrate and reaction specificity of Mycobacterium tuberculosis cytochrome P450 CYP121: insights from biochemical studies and crystal structures. |
10.1074/jbc.m112.443853 |
J. Biol. Chem. |
Substrate and reaction specificity of Mycobacterium tuberculosis cytochrome P450 CYP121: insights from biochemical studies and crystal structures.
Abstract
- Cytochrome P450 CYP121 is essential for the viability of Mycobacterium tuberculosis. Studies in vitro show that it can use the cyclodipeptide cyclo(l-Tyr-l-Tyr) (cYY) as a substrate. We report an investigation of the substrate and reaction specificities of CYP121 involving analysis of the interaction between CYP121 and 14 cYY analogues with various modifications of the side chains or the diketopiperazine (DKP) ring. Spectral titration experiments show that CYP121 significantly bound only cyclodipeptides with a conserved DKP ring carrying two aryl side chains in l-configuration. CYP121 did not efficiently or selectively transform any of the cYY analogues tested, indicating a high specificity for cYY. The molecular determinants of this specificity were inferred from both crystal structures of CYP121-analog complexes solved at high resolution and solution NMR spectroscopy of the analogues. Bound cYY or its analogues all displayed a similar set of contacts with CYP121 residues Asn(85), Phe(168), and Trp(182). The propensity of the cYY tyrosyl to point toward Arg(386) was dependent on the presence of the DKP ring that limits the conformational freedom of the ligand. The correct positioning of the hydroxyl of this tyrosyl was essential for conversion of cYY. Thus, the specificity of CYP121
Results from both a restricted binding specificity and a fine-tuned P450 substrate relationship. These
Results document the catalytic mechanism of CYP121 and improve our understanding of its function in vivo. This work contributes to progress toward the design of inhibitors of this essential protein of M. tuberculosis that could be used for antituberculosis therapy.
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| 23636399 |
Structures of the human and Drosophila 80S ribosome |
10.1038/nature12104. |
Nature |
Structures of the human and Drosophila 80S ribosome
Abstract
- Protein synthesis in all cells is carried out by macromolecular machines called ribosomes. Although the structures of prokaryotic, yeast and protist ribosomes have been determined, the more complex molecular architecture of metazoan 80S ribosomes has so far remained elusive. Here we present structures of Drosophila melanogaster and Homo sapiens 80S ribosomes in complex with the translation factor eEF2, E-site transfer RNA and Stm1-like proteins, based on high-resolution cryo-electron-microscopy density maps. These structures not only illustrate the co-evolution of metazoan-specific ribosomal RNA with ribosomal proteins but also reveal the presence of two additional structural layers in metazoan ribosomes, a well-ordered inner layer covered by a flexible RNA outer layer. The human and Drosophila ribosome structures will provide the basis for more detailed structural, biochemical and genetic experiments.
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| 23639361 |
Ghrelin receptor is activated by naringin and naringenin, constituents of a prokinetic agent Poncirus fructus |
10.1016/j.jep.2013.04.039. |
J Ethnopharmacol |
Ghrelin receptor is activated by naringin and naringenin, constituents of a prokinetic agent Poncirus fructus
Abstract
- Poncirus fructus (PF), also known as a dried immature fruit of Poncirus trifoliata (L.) Raf. (Rutaceae), has long been traditionally used for the various gastrointestinal disorders in Eastern Asia.
The aqueous extract of PF (PF-W) has the strong prokinetic effect, yet the underlying mechanism is still elusive. The present study investigated whether PF-W has any effect on motilin receptor or ghrelin receptor, since these receptors enhance intestinal motility when activated.
The effect of PF-W and its components on motilin or ghrelin receptor was determined by calcium imaging and whole-cell patch clamp methods.
PF-W activates the ghrelin receptor, but not the motilin receptor, resulting in a transient increase of intracellular calcium levels. Furthermore, among various constituents of PF, only naringin and naringenin evoked the intracellular calcium augmentation via the ghrelin receptor. Moreover, cortistatin-8 - a ghrelin receptor inhibitor - specifically blocked naringin- and naringenin-induced calcium increases. In addition, naringin and naringenin induced inward currents in ghrelin receptor-expressing cells under whole-cell patch clamp configuration.
PF-W activates the ghrelin receptor, and naringin and naringenin are key constituents responsible for the activation of ghrelin receptor. Therefore, the present study suggests that the ghrelin receptor is a molecular entity responsible for the strong prokinetic activity of PF-W.
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| 23658209 |
Integrins modulate the infection efficiency of West Nile virus into cells |
10.1099/vir.0.052613-0. |
J Gen Virol |
Integrins modulate the infection efficiency of West Nile virus into cells
Abstract
- The underlying mechanisms allowing West Nile virus (WNV) to replicate in a large variety of different arthropod, bird and mammal species are largely unknown but are believed to rely on highly conserved proteins relevant for viral entry and replication. Consistent with this, the integrin αvβ3 has been proposed lately to function as the cellular receptor for WNV. More recently published data, however, are not in line with this concept. Integrins are highly conserved among diverse taxa and are expressed by almost every cell type at high numbers. Our study was designed to clarify the involvement of integrins in WNV infection of cells. A cell culture model, based on wild-type and specific integrin knockout cell lines lacking the integrin subunits αv, β1 or β3, was used to investigate the susceptibility to WNV, and to evaluate binding and replication efficiencies of four distinct strains (New York 1999, Uganda 1937, Sarafend and Dakar). Though all cell lines were permissive, clear differences in replication efficiencies were observed. Rescue of the β3-integrin subunit resulted in enhanced WNV yields of up to 90 %, regardless of the virus strain used. Similar results were obtained for β1-expressing and non-expressing cells. Binding, however, was not affected by the expression of the integrins in question, and integrin blocking antibodies failed to have any effect. We conclude that integrins are involved in WNV infection but not at the level of binding to target cells.
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| 23662937 |
Sungsanpin, a lasso peptide from a deep-sea streptomycete |
10.1021/np300902g. |
J Nat Prod |
Sungsanpin, a lasso peptide from a deep-sea streptomycete
Abstract
- Sungsanpin (1), a new 15-amino-acid peptide, was discovered from a Streptomyces species isolated from deep-sea sediment collected off Jeju Island, Korea. The planar structure of 1 was determined by 1D and 2D NMR spectroscopy, mass spectrometry, and UV spectroscopy. The absolute configurations of the stereocenters in this compound were assigned by derivatizations of the hydrolysate of 1 with Marfey's reagents and 2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl isothiocyanate, followed by LC-MS analysis. Careful analysis of the ROESY NMR spectrum and three-dimensional structure calculations revealed that sungsanpin possesses the features of a lasso peptide: eight amino acids (-Gly(1)-Phe-Gly-Ser-Lys-Pro-Ile-Asp(8)-) that form a cyclic peptide and seven amino acids (-Ser(9)-Phe-Gly-Leu-Ser-Trp-Leu(15)) that form a tail that loops through the ring. Sungsanpin is thus the first example of a lasso peptide isolated from a marine-derived microorganism. Sungsanpin displayed inhibitory activity in a cell invasion assay with the human lung cancer cell line A549.
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