| 24072159 |
Promoter analysis and transcription regulation of fus gene cluster responsible for fusaricidin synthesis of Paenibacillus polymyxa SQR-21 |
10.1007/s00253-013-5157-6. |
Appl Microbiol Biotechnol |
Promoter analysis and transcription regulation of fus gene cluster responsible for fusaricidin synthesis of Paenibacillus polymyxa SQR-21
Abstract
- Fusaricidins produced by Paenibacillus polymyxa are lipopeptide antibiotics with outstanding antifungal activity. In this study, the whole gene cluster responsible for fusaricidin biosynthesis (fusA) was isolated and identified from the cDNA library of one biocontrol agent P. polymyxa SQR-21 (SQR-21). MALDI-TOF MS analysis confirmed that SQR-21 could produce four kinds of fusaricidins: A, B, C, and D. A central promoter that drove the transcription of fusGFEDCBA was revealed by mapping of the fus promoter region by 5' deletions. The disruption of fusA in SQR-21 led to the abolishment of fusaricidin production and antifungal activity. The direct interaction between a potential regulator, AbrB, and the promoter region of fus gene cluster was confirmed by electrophoretic mobility shift assays. One abrB disruption mutant showed significantly higher antifungal activity compared with the wild type. These results revealed a pathway for the transcriptional regulation of the fus gene cluster in P. polymyxa.
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| 24077967 |
Mechanism of action of novel lung edema therapeutic AP301 by activation of the epithelial sodium channel |
10.1124/mol.113.089409. |
Mol Pharmacol |
Mechanism of action of novel lung edema therapeutic AP301 by activation of the epithelial sodium channel
Abstract
- AP301 [Cyclo(CGQRETPEGAEAKPWYC)], a cyclic peptide comprising the human tumor necrosis factor lectin-like domain (TIP domain) sequence, is currently being developed as a treatment for lung edema and has been shown to reduce extravascular lung water and improve lung function in mouse, rat, and pig models. The current paradigm for liquid homeostasis in the adult mammalian lung is that passive apical uptake of sodium via the amiloride-sensitive epithelial Na⁺ channel (ENaC) and nonselective cyclic-nucleotide-gated cation channels creates the major driving force for reabsorption of water through the alveolar epithelium in addition to other ion channels such as potassium and chloride channels. AP301 can increase amiloride-sensitive current in A549 cells as well as in freshly isolated type II alveolar epithelial cells from different species. ENaC is expressed endogenously in all of these cell types. Consequently, this study was undertaken to determine whether ENaC is the specific target of AP301. The effect of AP301 in A549 cells as well as in human embryonic kidney cells and Chinese hamster ovary cells heterologously expressing human ENaC subunits (α, β, γ, and δ) was measured in patch clamp experiments. The congener TIP peptide AP318 [Cyclo(4-aminobutanoic acid-GQRETPEGAEAKPWYD)] activated ENaC by increasing single-channel open probability. AP301 increased current in proteolytically activated (cleaved) but not near-silent (uncleaved) ENaC in a reversible manner. αβγ- or δβγ-ENaC coexpression was required for maximal activity. No increase in current was observed after deglycosylation of extracellular domains of ENaC. Thus, our data suggest that the specific interaction of AP301 with both endogenously and heterologously expressed ENaC requires precedent binding to glycosylated extracellular loop(s).
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| 24080356 |
Characterizing the evolution and functions of the M-superfamily conotoxins |
10.1016/j.toxicon.2013.09.020. |
Toxicon |
Characterizing the evolution and functions of the M-superfamily conotoxins
Abstract
- Conotoxins from cone snails are valuable in physiology research and therapeutic applications. Evolutionary mechanisms of conotoxins have been investigated in several superfamilies, but there is no phylogenetic analysis on M-superfamily conotoxins. In this study, we characterized identical sequences, gene structure, novel cysteine frameworks, functions and evolutionary mechanisms of M-superfamily conotoxins. Identical M-superfamily conotoxins can be found in different Conus species from the analysis of novel 467 M-superfamily conotoxin sequences and other published M-superfamily conotoxins sequences. M-superfamily conotoxin genes consist of two introns and three exons from the results of genome walking. Eighteen cysteine frameworks were identified from the M-superfamily conotoxins, and 10 of the 18 may be generated from framework III. An analysis between diet types and phylogeny of the M-superfamily conotoxins indicate that M-superfamily conotoxins might not evolve in a concerted manner but were subject to birth-and-death evolution. Codon usage analysis shows that position-specific codon conservation is not restricted to cysteines, but also to other conserved residues. By analysing primary structures and physiological functions of M-superfamily conotoxins, we proposed a hypothesis that insertions and deletions, especially insertions in the third cysteine loop, are involved in the creation of new functions and structures of the M-superfamily conotoxins.
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| 24081691 |
Novel antifungal α-hairpinin peptide from Stellaria media seeds: structure, biosynthesis, gene structure and evolution |
10.1007/s11103-013-0127-z. |
Plant Mol Biol |
Novel antifungal α-hairpinin peptide from Stellaria media seeds: structure, biosynthesis, gene structure and evolution
Abstract
- Plant defense against disease is a complex multistage system involving initial recognition of the invading pathogen, signal transduction and activation of specialized genes. An important role in pathogen deterrence belongs to so-called plant defense peptides, small polypeptide molecules that present antimicrobial properties. Using multidimensional liquid chromatography, we isolated a novel antifungal peptide named Sm-AMP-X (33 residues) from the common chickweed (Stellaria media) seeds. The peptide sequence shows no homology to any previously described proteins. The peculiar cysteine arrangement (C(1)X3C(2)XnC(3)X3C(4)), however, allocates Sm-AMP-X to the recently acknowledged α-hairpinin family of plant defense peptides that share the helix-loop-helix fold stabilized by two disulfide bridges C(1)-C(4) and C(2)-C(3). Sm-AMP-X exhibits high broad-spectrum activity against fungal phytopathogens. We further showed that the N- and C-terminal "tail" regions of the peptide are important for both its structure and activity. The truncated variants Sm-AMP-X1 with both disulfide bonds preserved and Sm-AMP-X2 with only the internal S-S-bond left were progressively less active against fungi and presented largely disordered structure as opposed to the predominantly helical conformation of the full-length antifungal peptide. cDNA and gene cloning revealed that Sm-AMP-X is processed from a unique multimodular precursor protein that contains as many as 12 tandem repeats of α-hairpinin-like peptides. Structure of the sm-amp-x gene and two related pseudogenes sm-amp-x-ψ1 and sm-amp-x-ψ2 allows tracing the evolutionary scenario that led to generation of such a sophisticated precursor protein. Sm-AMP-X is a new promising candidate for engineering disease resistance in plants.
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| 24090274 |
Diverse synthesis of marine cyclic depsipeptide lagunamide A and its analogues |
10.1021/jo401687s. |
J Org Chem |
Diverse synthesis of marine cyclic depsipeptide lagunamide A and its analogues
Abstract
- The asymmetric total synthesis of lagunamide A (3.0%, 20 steps longest linear sequence) and its five analogues, including the structure dehydrated at the C37 position, are detailed in this report. The key feature in this diverse synthesis includes the elaboration of four consecutive chiral centers at C37-40 and the final macrocyclization. Starting from chiral aldehyde 10, we synthesized both 1,3-anti and 1,3-syn homoallylic alcohols 20a and 20b through asymmetric aldol condensation and stereoselective allylation. The following esterification to introduce the L-N-Me-Ala unit resulted in significant epimerization. This problem was finally overcome by coupling the alcohols with the corresponding acid chloride of the L-alanine derivative. The key α,β-unsaturated carboxylic acid unit was produced by cross-metathesis (CM) of methacrylaldehyde and related olefins. Interestingly, we found that the C7 configuration dramatically affected the ring closure. Natural lagunamide A (1a), its 39-epimer (1c), and its 2-epimer (1d) were obtained through macrolactamization between alanine and isoleucine moieties.
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| 24098653 |
High resolution crystal structure of the Grb2 SH2 domain with a phosphopeptide derived from CD28 |
10.1371/journal.pone.0074482. |
PLoS One |
High resolution crystal structure of the Grb2 SH2 domain with a phosphopeptide derived from CD28
Abstract
- Src homology 2 (SH2) domains play a critical role in cellular signal transduction. They bind to peptides containing phosphotyrosine (pY) with various specificities that depend on the flanking amino-acid residues. The SH2 domain of growth-factor receptor-bound protein 2 (Grb2) specifically recognizes pY-X-N-X, whereas the SH2 domains in phosphatidylinositol 3-kinase (PI3K) recognize pY-X-X-M. Binding of the pY site in CD28 (pY-M-N-M) by PI3K and Grb2 through their SH2 domains is a key step that triggers the CD28 signal transduction for T cell activation and differentiation. In this study, we determined the crystal structure of the Grb2 SH2 domain in complex with a pY-containing peptide derived from CD28 at 1.35 Å resolution. The peptide was found to adopt a twisted U-type conformation, similar to, but distinct from type-I β-turn. In all previously reported crystal structures, the peptide bound to the Grb2 SH2 domains adopts a type-I β-turn conformation, except those with a proline residue at the pY+3 position. Molecular modeling also suggests that the same peptide bound to PI3K might adopt a very different conformation.
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| 24113926 |
Synthesis of integerrimide A by an on-resin tandem Fmoc-deprotection-macrocyclisation approach |
10.1039/c3ob41447g. |
Org Biomol Chem |
Synthesis of integerrimide A by an on-resin tandem Fmoc-deprotection-macrocyclisation approach
Abstract
- A solid-phase total synthesis of integerrimide A (1) is reported. This work employs a safety-catch linker which enables head-to-tail cyclisation of the required linear peptide 6 as a method of cleaving the peptide from the solid support, and highlights a new tandem approach to direct macrocyclisation. It provides access to useful quantities of 1 in 16 steps and 19% overall yield, based on the manufacturer's stated resin substitution from commercially available materials, and also verifies the absolute stereochemistry of the natural product.
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| 24122487 |
Design and synthesis of α-conotoxin GID analogues as selective α4β2 nicotinic acetylcholine receptor antagonists |
10.1002/bip.22413. |
Biopolymers |
Design and synthesis of α-conotoxin GID analogues as selective α4β2 nicotinic acetylcholine receptor antagonists
Abstract
- The α4β2 nicotinic acetylcholine receptor (nAChR) is an important target for currently approved smoking cessation therapeutics. However, the development of highly selective α4β2 nAChR antagonists remains a significant challenge. α-Conotoxin GID is an antagonist of α4β2 nAChRs, though it is significantly more potent toward the α3β2 and α7 subtypes. With the goal of obtaining further insights into α-conotoxin GID/nAChR interactions that could lead to the design of GID analogues with improved affinity for α4β2 nAChRs, we built a homology model of the GID/α4β2 complex using an X-ray co-crystal structure of an α-conotoxin/acetylcholine binding protein (AChBP) complex. Several additional interactions that could potentially enhance the affinity of GID for α4β2 nAChRs were observed in our model, which led to the design and synthesis of 22 GID analogues. Seven analogues displayed inhibitory activity toward α4β2 nAChRs that was comparable to GID. Significantly, both GID[A10S] and GID[V13I] demonstrated moderately improved selectivity toward α4β2 over α3β2 when compared with GID, while GID[V18N] exhibited no measurable inhibitory activity for the α3β2 subtype, yet retained inhibitory activity for α4β2. In this regard, GID[V18N] is the most α4β2 nAChR selective α-conotoxin analogue identified to date.
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| 24131469 |
Systematic interrogation of the Conus marmoreus venom duct transcriptome with ConoSorter reveals 158 novel conotoxins and 13 new gene superfamilies |
10.1186/1471-2164-14-708. |
BMC Genomics |
Systematic interrogation of the Conus marmoreus venom duct transcriptome with ConoSorter reveals 158 novel conotoxins and 13 new gene superfamilies
Abstract
- Conopeptides, often generically referred to as conotoxins, are small neurotoxins found in the venom of predatory marine cone snails. These molecules are highly stable and are able to efficiently and selectively interact with a wide variety of heterologous receptors and channels, making them valuable pharmacological probes and potential drug leads. Recent advances in next-generation RNA sequencing and high-throughput proteomics have led to the generation of large data sets that require purpose-built and dedicated bioinformatics tools for efficient data mining.
Here we describe ConoSorter, an algorithm that categorizes cDNA or protein sequences into conopeptide superfamilies and classes based on their signal, pro- and mature region sequence composition. ConoSorter also catalogues key sequence characteristics (including relative sequence frequency, length, number of cysteines, N-terminal hydrophobicity, sequence similarity score) and automatically searches the ConoServer database for known precursor sequences, facilitating identification of known and novel conopeptides. When applied to ConoServer and UniProtKB/Swiss-Prot databases, ConoSorter is able to recognize 100% of known conotoxin superfamilies and classes with a minimum species specificity of 99%. As a proof of concept, we performed a reanalysis of Conus marmoreus venom duct transcriptome and (i) correctly classified all sequences previously annotated, (ii) identified 158 novel precursor conopeptide transcripts, 106 of which were confirmed by protein mass spectrometry, and (iii) identified another 13 novel conotoxin gene superfamilies.
Taken together, these findings indicate that ConoSorter is not only capable of robust classification of known conopeptides from large RNA data sets, but can also facilitate de novo identification of conopeptides which may have pharmaceutical importance.
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| 24142738 |
Pharmacokinetic and pharmacodynamic properties of batifiban coadministered with antithrombin agents in Chinese healthy volunteers |
10.1007/s11596-013-1198-4. |
J Huazhong Univ Sci Technolog Med Sci |
Pharmacokinetic and pharmacodynamic properties of batifiban coadministered with antithrombin agents in Chinese healthy volunteers
Abstract
- The combined use of batifiban, a synthetic platelet GPII b/ IIIa receptor antagonist, and antithrombin agents is an attractive option for the treatment of patients with non-ST-segment elevation (NSTE) acute coronary syndrome (ACS) and those scheduled for percutaneous coronary intervention. To observe whether antithrombin agents affect the pharmacokinetic and pharmacodynamic properties of batifiban in combination therapy and optimize clinical administration dosage of batifiban, an open-label and parallel study was conducted. Thirty healthy subjects were randomly divided into three groups, which were sequentially treated with batifiban alone, or oral coadministration of clopidogrel, aspirin and UFH, or batifiban coadministered with these antithrombin agents. Blood samples were collected at pre-specified time points. The evaluation index included the inhibition of platelet aggregation and pharmacokinetic parameters. The pharmacokinetic parameters of batifiban and batifiban coadministered with antithrombin agents showed no significant differences. The mean inhibition rate of platelet aggregation (%) suggested that neither batifiban alone nor antithrombin agents alone could provide such potent inhibition rate (>80%) to obtain the best clinical efficacy, but they had a synergistic effect on platelet inhibition. No serious adverse effects were observed. The results in these healthy subjects suggest that batifiban coadministrated with antithrombin agents could achieve optimum clinical treatment effect for patients with NSTE ACS, and also those scheduled for percutaneous coronary intervention.
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| 24169519 |
20 ans après: a second mutation in MAOA identified by targeted high-throughput sequencing in a family with altered behavior and cognition |
10.1038/ejhg.2013.243. |
Eur J Hum Genet |
20 ans après: a second mutation in MAOA identified by targeted high-throughput sequencing in a family with altered behavior and cognition
Abstract
- Intellectual disability (ID) is characterized by an extraordinary genetic heterogeneity, with >250 genes that have been implicated in monogenic forms of ID. Because this complexity precluded systematic testing for mutations and because clinical features are often non-specific, for some of these genes only few cases or families have been unambiguously documented. It is the case of the X-linked gene encoding monoamine oxidase A (MAOA), for which only one nonsense mutation has been identified in Brunner syndrome, characterized in a single family by mild non-dysmorphic ID and impulsive, violent and aggressive behaviors. We have performed targeted high-throughput sequencing of 220 genes, including MAOA, in patients with undiagnosed ID. We identified a c.797_798delinsTT (p.C266F) missense mutation in MAOA in a boy with autism spectrum disorder, attention deficit and autoaggressive behavior. Two maternal uncles carry the mutation and have severe ID, with a history of maltreatment in early childhood. This novel missense mutation decreases MAOA enzymatic activity, leading to abnormal levels of urinary monoamines. The identification of this new point mutation confirms, for the first time since 1993, the monogenic implication of the MAOA gene in ID of various degrees, autism and behavioral disturbances. The variable expressivity of the mutation observed in male patients of this family may involve gene-environment interactions, and the identification of a perturbation in monoamine metabolism should be taken into account when prescribing psychoactive drugs in such patients.
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| 24195442 |
Structure elucidation and antimalarial activity of apicidin F: an apicidin-like compound produced by Fusarium fujikuroi |
10.1021/np4006053. |
J Nat Prod |
Structure elucidation and antimalarial activity of apicidin F: an apicidin-like compound produced by Fusarium fujikuroi
Abstract
- Apicidins are cyclic tetrapeptides with histone deacetylase inhibitory activity. Since their discovery in 1996 a multitude of studies concerning the activity against protozoa and certain cancer cell lines of natural and synthetic apicidin analogues have been published. Until now, the only published natural sources of apicidin are the fungus Fusarium pallidoroseum, later known as F. semitectum and two unspecified Fusarium strains. The biosynthetic origin of apicidins could be associated with a gene cluster, and a biosynthetic pathway has been proposed. Recently, our group was able to identify for the first time an apicidin-like gene cluster in F. fujikuroi that apparently does not lead to the production of any known apicidin analogue. By overexpressing the pathway-specific transcription factor we were able to identify a new apicidin-like compound. The present study provides the complete structure elucidation of the new compound, named apicidin F. Activity evaluation against Plasmodium falciparum showed good in vitro activity with an IC50 value of 0.67 μM.
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| 24200193 |
Characterization of a novel α-conotoxin TxID from Conus textile that potently blocks rat α3β4 nicotinic acetylcholine receptors |
10.1021/jm401254c. |
J Med Chem |
Characterization of a novel α-conotoxin TxID from Conus textile that potently blocks rat α3β4 nicotinic acetylcholine receptors
Abstract
- The α3β4 nAChRs are implicated in pain sensation in the PNS and addiction to nicotine in the CNS. We identified an α-4/6-conotoxin (CTx) TxID from Conus textile. The new toxin consists of 15 amino acid residues with two disulfide bonds. TxID was synthesized using solid phase methods, and the synthetic peptide was functionally tested on nAChRs heterologously expressed in Xenopus laevis oocytes. TxID blocked rat α3β4 nAChRs with a 12.5 nM IC50, which places it among the most potent α3β4 nAChR antagonists. TxID also blocked the closely related α6/α3β4 with a 94 nM IC50 but showed little activity on other nAChR subtypes. NMR analysis showed that two major structural isomers exist in solution, one of which adopts a regular α-CTx fold but with different surface charge distribution to other 4/6 family members. α-CTx TxID is a novel tool with which to probe the structure and function of α3β4 nAChRs.
|
| 24211019 |
Truncated and constrained helical analogs of antimicrobial esculentin-2EM |
10.1016/j.bmcl.2013.10.031. |
Bioorg Med Chem Lett |
Truncated and constrained helical analogs of antimicrobial esculentin-2EM
Abstract
- Esculentin-2EM is a 37-residue, cationic, amphipathic, α-helical antimicrobial peptide isolated from a Korean frog, Glandirama emeljanovi. Many studies revealed that truncation of this peptide results in substantial decreases in its antimicrobial activity. Lee and his colleagues have recently reported that a 23-residue esculentin-2EM analog containing a tryptophanyl substitution at position 16 showed a significant recovery of the antimicrobial activity of the parent peptide. Here we report a new series of 15-residue esculentin-2EM analogs which are constrained into an α-helical conformation via an oct-4-enyl cross-link. The resulting 'stapled' derivatives displayed remarkable increases not only in antimicrobial activity but also in helical content and protease resistance compared to Lee's original 23-residue esculentin-2EM analog. The preliminary data obtained in this work strongly supports the potential of our strategy for the development of a new class of peptide antibiotics.
|
| 24252114 |
Rescuing biological activity from synthetic phakellistatin 19 |
10.1021/jm401520x. |
J Med Chem |
Rescuing biological activity from synthetic phakellistatin 19
Abstract
- Phakellistatins is one of the families of Pro-rich cyclic peptides whose synthetic counterparts have revealed cytotoxicities that differ greatly from those displayed by their corresponding natural ones. This is also the case of the last member isolated from this family, phakellistatin19, an octacyclopeptide containing three Pro moieties and a high percentage of apolar residues. Exhaustive NMR studies on the synthetic and natural phakellistatin 19 have been performed in order to find a plausible explanation for this intriguing behavior. Moreover, taking advantage of phakellistatin's framework, analogues with different cis/trans geometry at the key prolyl peptide bonds were designed, covering a promising conformational space that could not be reached by the natural peptide. By introduction of proline surrogates (Ψ(Me,Me)pro residues) in phakellistatin 19, which effectively increases the percentage of cis conformation in the final peptides, this translates into enhanced biological activity, therefore "rescuing" an otherwise inactive cyclopeptide.
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