| 22047802 |
The arginine mimicking β-amino acid β³hPhe(3-H₂N-CH₂) as S1 ligand in cyclotheonamide-based β-tryptase inhibitors |
10.1016/j.bmc.2011.09.050. |
Bioorg Med Chem |
The arginine mimicking β-amino acid β³hPhe(3-H₂N-CH₂) as S1 ligand in cyclotheonamide-based β-tryptase inhibitors
Abstract
- β-Tryptase, a mast-cell specific serine protease with trypsin-like activity, has emerged in the last years as a promising novel therapeutic target in the field of allergic inflammation. Recently, we have developed a potent and selective β-tryptase inhibitor based on the natural product cyclotheonamide E4 by implementing a basic P3 residue that addresses the determinants of the extended substrate specificity of β-tryptase. To further improve the affinity/selectivity profile of this lead structure, we have now investigated β-homo-3-aminomethylphenylalanine as S1 ligand. In contrast to the corresponding β-homo amino acids derived from lysine or arginine, we demonstrate that this particular basic β-homo amino acid is a privileged S1 ligand for the development of β-tryptase inhibitors. Besides affinity, selectivity and reduced basicity, these novel cyclotheonamide E4 analogs show excellent stability in human plasma and serum.
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| 22074926 |
Identification and structural characterization of novel cyclotide with activity against an insect pest of sugar cane |
10.1074/jbc.M111.294009. |
J Biol Chem |
Identification and structural characterization of novel cyclotide with activity against an insect pest of sugar cane
Abstract
- Cyclotides are a family of plant-derived cyclic peptides comprising six conserved cysteine residues connected by three intermolecular disulfide bonds that form a knotted structure known as a cyclic cystine knot (CCK). This structural motif is responsible for the pronounced stability of cyclotides against chemical, thermal, or proteolytic degradation and has sparked growing interest in this family of peptides. Here, we isolated and characterized a novel cyclotide from Palicourea rigida (Rubiaceae), which was named parigidin-br1. The sequence indicated that this peptide is a member of the bracelet subfamily of cyclotides. Parigidin-br1 showed potent insecticidal activity against neonate larvae of Lepidoptera (Diatraea saccharalis), causing 60% mortality at a concentration of 1 μm but had no detectable antibacterial effects. A decrease in the in vitro viability of the insect cell line from Spodoptera frugiperda (SF-9) was observed in the presence of parigidin-br1, consistent with in vivo insecticidal activity. Transmission electron microscopy and fluorescence microscopy of SF-9 cells after incubation with parigidin-br1 or parigidin-br1-fluorescein isothiocyanate, respectively, revealed extensive cell lysis and swelling of cells, consistent with an insecticidal mechanism involving membrane disruption. This hypothesis was supported by in silico analyses, which suggested that parigidin-br1 is able to complex with cell lipids. Overall, the results suggest promise for the development of parigidin-br1 as a novel biopesticide.
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| 22091906 |
Total synthesis and stereochemical assignment of burkholdac B, a depsipeptide HDAC inhibitor |
10.1021/ol202197q. |
Org Lett |
Total synthesis and stereochemical assignment of burkholdac B, a depsipeptide HDAC inhibitor
Abstract
- Three diastereomers of burkholdac B were prepared by total synthesis, enabling the full stereochemical assignment of the natural product. It is proposed that burkholdac B is identical to thailandepsin A independently isolated by Cheng from the same strain of Burkholderia thailandensis . Burkholdac B is the most potent among depsipeptide histone deacetylase inhibitors in growth inhibition of the MCF7 breast cancer cell line with an IC(50) of 60 pM.
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| 22108175 |
RegIIA: an α4/7-conotoxin from the venom of Conus regius that potently blocks α3β4 nAChRs |
10.1016/j.bcp.2011.11.006. |
Biochem Pharmacol |
RegIIA: an α4/7-conotoxin from the venom of Conus regius that potently blocks α3β4 nAChRs
Abstract
- Neuronal nicotinic acetylcholine receptors (nAChRs) play pivotal roles in the central and peripheral nervous systems. They are implicated in disease states such as Parkinson's disease and schizophrenia, as well as addictive processes for nicotine and other drugs of abuse. Modulation of specific nAChRs is essential to understand their role in the CNS. α-Conotoxins, disulfide-constrained peptides isolated from the venom of cone snails, potently inhibit nAChRs. Their selectivity varies markedly depending upon the specific nAChR subtype/α-conotoxin pair under consideration. Thus, α-conotoxins are excellent probes to evaluate the functional roles of nAChRs subtypes. We isolated an α4/7-conotoxin (RegIIA) from the venom of Conus regius. Its sequence was determined by Edman degradation and confirmed by sequencing the cDNA of the protein precursor. RegIIA was synthesized using solid phase methods and native and synthetic RegIIA were functionally tested using two-electrode voltage clamp recording on nAChRs expressed in Xenopus laevis oocytes. RegIIA is among the most potent antagonist of the α3β4 nAChRs found to date and is also active at α3β2 and α7 nAChRs. The 3D structure of RegIIA reveals the typical folding of most α4/7-conotoxins. Thus, while structurally related to other α4/7 conotoxins, RegIIA has an exquisite balance of shape, charge, and polarity exposed in its structure to potently block the α3β4 nAChRs.
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| 22134246 |
Thiostrepton, proteasome inhibitors and FOXM1 |
10.4161/cc.10.24.18544. |
Cell Cycle |
Thiostrepton, proteasome inhibitors and FOXM1
Abstract
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| 22152977 |
Lyngbyaureidamides A and B, two anabaenopeptins from the cultured freshwater cyanobacterium Lyngbya sp. (SAG 36.91) |
10.1016/j.phytochem.2011.09.017. |
Phytochemistry |
Lyngbyaureidamides A and B, two anabaenopeptins from the cultured freshwater cyanobacterium Lyngbya sp. (SAG 36.91)
Abstract
- Two anabaenopeptin-type peptides, lyngbyaureidamides A and B, together with two previously reported peptides lyngbyazothrins C and D, were isolated from the cultured freshwater cyanobacterium Lyngbya sp. (SAG 36.91). Their structures were determined by spectroscopic and chemical methods. Lyngbyazothrins C and D were also able to inhibit the 20S proteasome with IC(50) values of 7.1 μM and 19.2 μM, respectively, while lyngbyaureidamides A and B were not active at 50 μM.
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| 22153873 |
Persipeptides A and B, two cyclic peptides from Streptomyces sp. UTMC 1154 |
10.1016/j.bmc.2011.10.076. |
Bioorg Med Chem |
Persipeptides A and B, two cyclic peptides from Streptomyces sp. UTMC 1154
Abstract
- Two new N-methylated cyclopeptides, persipeptide A (1) and B (2), have been isolated from Streptomyces sp. UTMC1154. Their structures were established using 1D and 2D NMR experiments. 2D TOCSY experiments were applied to identify the amino acid residues, while HMBC correlations were used to determine their sequence. According to Marfey's method, all amino acids had the l-configuration. The two cyclic peptides had the same ring size and amino acid composition, but differed in their sequence; they did not show activity against the tested bacteria, fungi and algae. Molecular identification experiments placed the strain in the genus Streptomyces closely related to Streptomyces coerulescens DSM40146(T) (99.45%) and Streptomyces varsoviensis DSM40346(T) (99.25%).
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| 22171320 |
Human urinary glycoproteomics; attachment site specific analysis of N- and O-linked glycosylations by CID and ECD. |
10.1074/mcp.m111.013649 |
Mol. Cell. |
Human urinary glycoproteomics; attachment site specific analysis of N- and O-linked glycosylations by CID and ECD.
Abstract
- Urine is a complex mixture of proteins and waste products and a challenging biological fluid for biomarker discovery. Previous proteomic studies have identified more than 2800 urinary proteins but analyses aimed at unraveling glycan structures and glycosylation sites of urinary glycoproteins are lacking. Glycoproteomic characterization remains difficult because of the complexity of glycan structures found mainly on asparagine (N-linked) or serine/threonine (O-linked) residues. We have developed a glycoproteomic approach that combines efficient purification of urinary glycoproteins/glycopeptides with complementary MS-fragmentation techniques for glycopeptide analysis. Starting from clinical sample size, we eliminated interfering urinary compounds by dialysis and concentrated the purified urinary proteins by lyophilization. Sialylated urinary glycoproteins were conjugated to a solid support by hydrazide chemistry and trypsin digested. Desialylated glycopeptides, released through mild acid hydrolysis, were characterized by tandem MS experiments utilizing collision induced dissociation (CID) and electron capture dissociation fragmentation techniques. In CID-MS(2), Hex(5)HexNAc(4)-N-Asn and HexHexNAc-O-Ser/Thr were typically observed, in agreement with known N-linked biantennary complex-type and O-linked core 1-like structures, respectively. Additional glycoforms for specific N- and O-linked glycopeptides were also identified, e.g. tetra-antennary N-glycans and fucosylated core 2-like O-glycans. Subsequent CID-MS(3), of selected fragment-ions from the CID-MS(2) analysis, generated peptide specific b- and y-ions that were used for peptide identification. In total, 58 N- and 63 O-linked glycopeptides from 53 glycoproteins were characterized with respect to glycan- and peptide sequences. The combination of CID and electron capture dissociation techniques allowed for the exact identification of Ser/Thr attachment site(s) for 40 of 57 putative O-glycosylation sites. We defined 29 O-glycosylation sites which have, to our knowledge, not been previously reported. This is the first study of human urinary glycoproteins where "intact" glycopeptides were studied, i.e. the presence of glycans and their attachment sites were proven without doubt.
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| 22179831 |
Deubiquitination of EGFR by Cezanne-1 contributes to cancer progression |
10.1038/onc.2011.587. |
Oncogene |
Deubiquitination of EGFR by Cezanne-1 contributes to cancer progression
Abstract
- Once stimulated, the epidermal growth factor receptor (EGFR) undergoes self-phosphorylation, which, on the one hand, instigates signaling cascades, and on the other hand, recruits CBL ubiquitin ligases, which mark EGFRs for degradation. Using RNA interference screens, we identified a deubiquitinating enzyme, Cezanne-1, that opposes receptor degradation and enhances EGFR signaling. These functions require the catalytic- and ubiquitin-binding domains of Cezanne-1, and they involve physical interactions and transphosphorylation of Cezanne-1 by EGFR. In line with the ability of Cezanne-1 to augment EGF-induced growth and migration signals, the enzyme is overexpressed in breast cancer. Congruently, the corresponding gene is amplified in approximately one third of mammary tumors, and high transcript levels predict an aggressive disease course. In conclusion, deubiquitination by Cezanne-1 curtails degradation of growth factor receptors, thereby promotes oncogenic growth signals.
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| 22195566 |
Paenibacillus polymyxa PKB1 produces variants of polymyxin B-type antibiotics |
10.1016/j.chembiol.2011.09.017. |
Chem Biol |
Paenibacillus polymyxa PKB1 produces variants of polymyxin B-type antibiotics
Abstract
- Polymyxins are cationic lipopeptide antibiotics active against many species of Gram-negative bacteria. We sequenced the gene cluster for polymyxin biosynthesis from Paenibacillus polymyxa PKB1. The 40.8 kb gene cluster comprises three nonribosomal peptide synthetase-encoding genes and two ABC transporter-like genes. Disruption of a peptide synthetase gene abolished all antibiotic production, whereas deletion of one or both transporter genes only reduced antibiotic production. Computational analysis of the peptide synthetase modules suggested that the enzyme system produces variant forms of polymyxin B (1 and 2), with D-2,4-diaminobutyrate instead of L-2,4-diaminobutyrate in amino acid position 3. Two antibacterial metabolites were resolved by HPLC and identified by high-resolution mass spectrometry and MS/MS sequencing as the expected variants 3 and 4 of polymyxin B(1) (1) and B(2) (2). Stereochemical analysis confirmed the presence of both D-2,4-diaminobutyrate and L-2,4-diaminobutyrate residues.
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| 22215668 |
γδ T cell receptors recognize the non-classical major histocompatibility complex (MHC) molecule T22 via conserved anchor residues in a MHC peptide-like fashion |
10.1074/jbc.M111.333153. |
J Biol Chem |
γδ T cell receptors recognize the non-classical major histocompatibility complex (MHC) molecule T22 via conserved anchor residues in a MHC peptide-like fashion
Abstract
- The molecular mechanisms by which γδ T cells recognize ligand remain a mystery. The non-classical MHC molecule T22 represents the best characterized ligand for murine γδ T cells, with a motif (W … EGYEL) present in the γδ T cell receptor complementary-determining region 3δ (CDR3δ) loop mediating γδ T cell recognition of this molecule. Produced through V(D)J recombination, this loop is quite diverse, with different numbers and chemical types of amino acids between Trp and EGYEL, which have unknown functional consequences for T22 recognition. We have investigated the biophysical and structural effects of CDR3δ loop diversity, revealing a range of affinities for T22 but a common thermodynamic pattern. Mutagenesis of these CDR3δ loops defines the key anchor residues involved in T22 recognition as W … EGYEL, similar to those found for the G8 CDR3δ loop, and demonstrates that spacer residues modulate but are not required for T22 recognition. Comparison of the location of these residues in the T22 interface reveals a striking similarity to peptide anchor residues in classically presented MHC peptides, with the key Trp residue of the CDR3δ motif completing the deficient peptide-binding groove of T22. This suggests that γδ T cell recognition of T22 utilizes the conserved ligand-presenting nature of the MHC fold.
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| 22229737 |
A novel µ-conopeptide, CnIIIC, exerts potent and preferential inhibition of NaV1.2/1.4 channels and blocks neuronal nicotinic acetylcholine receptors |
10.1111/j.1476-5381.2012.01837.x. |
Br J Pharmacol |
A novel µ-conopeptide, CnIIIC, exerts potent and preferential inhibition of NaV1.2/1.4 channels and blocks neuronal nicotinic acetylcholine receptors
Abstract
- The µ-conopeptide family is defined by its ability to block voltage-gated sodium channels (VGSCs), a property that can be used for the development of myorelaxants and analgesics. We characterized the pharmacology of a new µ-conopeptide (µ-CnIIIC) on a range of preparations and molecular targets to assess its potential as a myorelaxant.
µ-CnIIIC was sequenced, synthesized and characterized by its direct block of elicited twitch tension in mouse skeletal muscle and action potentials in mouse sciatic and pike olfactory nerves. µ-CnIIIC was also studied on HEK-293 cells expressing various rodent VGSCs and also on voltage-gated potassium channels and nicotinic acetylcholine receptors (nAChRs) to assess cross-interactions. Nuclear magnetic resonance (NMR) experiments were carried out for structural data.
Synthetic µ-CnIIIC decreased twitch tension in mouse hemidiaphragms (IC(50) = 150 nM), and displayed a higher blocking effect in mouse extensor digitorum longus muscles (IC = 46 nM), compared with µ-SIIIA, µ-SmIIIA and µ-PIIIA. µ-CnIIIC blocked Na(V)1.4 (IC(50) = 1.3 nM) and Na(V)1.2 channels in a long-lasting manner. Cardiac Na(V)1.5 and DRG-specific Na(V)1.8 channels were not blocked at 1 µM. µ-CnIIIC also blocked the α3β2 nAChR subtype (IC(50) = 450 nM) and, to a lesser extent, on the α7 and α4β2 subtypes. Structure determination of µ-CnIIIC revealed some similarities to α-conotoxins acting on nAChRs.
µ-CnIIIC potently blocked VGSCs in skeletal muscle and nerve, and hence is applicable to myorelaxation. Its atypical pharmacological profile suggests some common structural features between VGSCs and nAChR channels.
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| 22246221 |
Extractive fermentation for enhanced production of thailandepsin A from Burkholderia thailandensis E264 using polyaromatic adsorbent resin Diaion HP-20 |
10.1007/s10295-011-1073-x |
J Ind Microbiol Biotechnol |
Extractive fermentation for enhanced production of thailandepsin A from Burkholderia thailandensis E264 using polyaromatic adsorbent resin Diaion HP-20
Abstract
- Thailandepsin A is natural product of Burkholderia thailandensis E264 with potent histone deacetylase inhibitory activities and promising anticancer activities. The titer of thailandepsin A is very low (less than 10 mg/l) from limited empirical fermentation. To facilitate preclinical evaluations and potentially clinical development of thailandepsin A, systematic optimization and extractive fermentation of thailandepsin A from B. thailandensis E264 culture in flasks were investigated in this pilot study. The main fermentation parameters--28°C, pH 7.0, inoculum ratio 1% (v/v), incubation duration 60 h, medium volume 26%, shaking speed 170 rpm, and chloroform as extracting solvent--were determined by single factor experiments. Polyaromatic adsorbent resin Diaion HP-20, when added at a concentration of 4% (w/v), was most effective to reduce feedback inhibition of thailandepsin A and to significantly increase the titer of target product. Central composite design was used to further optimize the fermentation medium for B. thailandensis E264. The optimized medium contains glucose 17.89 g/l, tryptone 34.98 g/l, potassium phosphate 24.84 g/l, and sodium citrate 0.01 g/l, which resulted in a large increase of the titer of thailandepsin A to 236.7 mg/l. Finally kinetic models based on the modified logistic and Luedeking-Piret equations were developed, delivering a good description of temporal variations of biomass, product, and substrate in the fermentation process, which could be used as references for developing large-scale fermentation.
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| 22260773 |
Stylissamide X, a new proline-rich cyclic octapeptide as an inhibitor of cell migration, from an Indonesian marine sponge of Stylissa sp |
10.1016/j.bmcl.2011.10.023. |
Bioorg Med Chem Lett |
Stylissamide X, a new proline-rich cyclic octapeptide as an inhibitor of cell migration, from an Indonesian marine sponge of Stylissa sp
Abstract
- A new proline-rich cyclic octapeptide named stylissamide X (1) was isolated from an Indonesian marine sponge of Stylissa sp. as an inhibitor of cell migration from the guidance of wound-healing assay. The chemical structure of stylissamide X (1) was determined on the basis of spectroscopic analysis, and stereostructure of the amino acids were deduced by Marfey's method. Compound 1 showed inhibitory activity against migration of HeLa cells in the ranges of 0.1-10 μM concentration through both wound-healing assay and chemotaxicell chamber assay, while the cell viability was maintained more than 75% up to 10 μM concentration of 1.
|
| 22298428 |
The Ankrd 13 family of UIM-bearing proteins regulates EGF receptor endocytosis from the plasma membrane |
10.1091/mbc.E11-09-0817. |
Mol Biol Cell |
The Ankrd 13 family of UIM-bearing proteins regulates EGF receptor endocytosis from the plasma membrane
Abstract
- The mechanism of ubiquitin-dependent endocytosis of cell surface proteins is not completely understood. Here we examine the role of the ankyrin repeat domain (Ankrd) 13A, 13B, and 13D proteins, which constitute a functionally unknown family of ubiquitin-interacting motif (UIM)-bearing proteins, in the process. Stimulation of human HeLa cells with epidermal growth factor (EGF) rapidly induced direct binding of Ankrd 13 proteins to ubiquitinated EGF receptor (EGFR) via the UIMs. The binding was inhibited when the Ankrd 13 proteins underwent UIM-dependent monoubiquitination, suggesting that their activity is regulated by ubiquitination of themselves. Ankrd 13 proteins bound specifically to Lys-63-linked ubiquitin chains, which was consistent with a previous report that EGFR mainly undergoes Lys-63-linked polyubiquitination. Ankrd 13 proteins were anchored, via the central region and UIMs, to the plasma membrane, where they colocalized with EGFR. Finally, overexpression of wild-type as well as truncated-mutant Ankrd 13 proteins strongly inhibited rapid endocytosis of ubiquitinated EGFR from the surface in EGF-treated cells. We conclude that by binding to the Lys-63-linked polyubiquitin moiety of EGFR at the plasma membrane, Ankrd 13 proteins regulate the rapid internalization of ligand-activated EGFR.
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