| 21948835 |
Identification and characterization of leucocyclicin Q, a novel cyclic bacteriocin produced by Leuconostoc mesenteroides TK41401 |
10.1128/AEM.06348-11. |
Appl Environ Microbiol |
Identification and characterization of leucocyclicin Q, a novel cyclic bacteriocin produced by Leuconostoc mesenteroides TK41401
Abstract
- The culture supernatant of Leuconostoc mesenteroides TK41401, isolated from Japanese pickles, possessed antimicrobial activity against broad range of a bacterial genera and particularly strong activity against Bacillus coagulans, the major contaminant of pickles. An antimicrobial peptide was purified in three chromatographic steps, and its molecular mass was determined to be 6,115.59 Da by electrospray ionization time-of-flight mass spectrometry (ESI-TOF MS). The primary structure of this peptide was determined by amino acid and DNA sequencing, and these analyses revealed that it was translated as a 63-residue precursor. This precursor showed high similarity to the precursor of lactocyclicin Q, a cyclic bacteriocin produced by Lactococcus sp. strain QU 12. The molecular weight calculated after cyclization, which was presumed to involve the same process as in lactocyclicin Q (between L3 and W63), agreed with that estimated by ESI-TOF MS. This peptide was proved to be a novel cyclic bacteriocin, and it was termed leucocyclicin Q. The antimicrobial spectrum of this bacteriocin clearly differed from that of lactocyclicin Q, even though their primary structures were quite similar. This is the first report of a cyclic bacteriocin produced by a strain of the genus Leuconostoc.
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| 21965678 |
SUMOylation and SUMO-interacting motif (SIM) of metastasis tumor antigen 1 (MTA1) synergistically regulate its transcriptional repressor function |
10.1074/jbc.M111.267237. |
J Biol Chem |
SUMOylation and SUMO-interacting motif (SIM) of metastasis tumor antigen 1 (MTA1) synergistically regulate its transcriptional repressor function
Abstract
- Metastasis tumor antigen 1 (MTA1), a component of the Mi-2·nucleosome remodeling and deacetylase complex, plays a crucial role in gene transcription, but the mechanism involved remains largely unknown. Here, we report that MTA1 is a substrate for small ubiquitin-related modifier 2/3 (SUMO2/3) in vivo. Protein inhibitor of activated STAT (PIAS) proteins enhance SUMOylation of MTA1 and may participate in paralog-selective SUMOylation, whereas sentrin/SUMO-specific protease 1 (SENP1) and 2 may act as deSUMOylation enzymes for MTA1. Moreover, MTA1 contains a functional SUMO-interacting motif (SIM) at its C terminus, and SIM is required for the efficient SUMOylation of MTA1. SUMO conjugation on Lys-509, which is located within the SUMO consensus site, together with SIM synergistically regulates the co-repressor activity of MTA1 on PS2 transcription, probably by recruiting HDAC2 onto the PS2 promoter. Interestingly, MTA1 may up-regulate the expression of SUMO2 via interaction with RNA polymerase II and SP1 at the SUMO2 promoter. These findings not only provide novel mechanistic insights into the regulation of the transcriptional repressor function of MTA1 by SUMOylation and SIM but also uncover a potential function of MTA1 in modulating the SUMOylation pathway.
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| 21967034 |
Isolation of talathermophilins from the thermophilic fungus Talaromyces thermophilus YM3-4 |
10.1021/np200365z. |
J Nat Prod |
Isolation of talathermophilins from the thermophilic fungus Talaromyces thermophilus YM3-4
Abstract
- Six indole alkaloids with various levels of prenylation were isolated from the thermophilic fungus Talaromyces thermophilus strain YM3-4. Their structures were identified by NMR and MS spectroscopic analyses. Compounds 1 and 2 are new analogues of the key versatile precursor notoamide E. Compound 3 is a novel analogue of preechinulin, and compound 4 was reported as a natural occurring cyclo(glycyltryptophyl) for the first time. The metabolite profile of this thermophilic organism displayed a biosynthetic pathway for talathermophilins.
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| 21967146 |
Histone deacetylase inhibitors from Burkholderia thailandensis |
10.1021/np200532d. |
J Nat Prod |
Histone deacetylase inhibitors from Burkholderia thailandensis
Abstract
- Bioactivity-guided fractionation of an extract of Burkholderia thailandensis led to the isolation and identification of a new cytotoxic depsipeptide and its dimer. Both compounds potently inhibited the function of histone deacetylases 1 and 4. The monomer, spiruchostatin C (2), was tested side by side with the clinical depsipeptide FK228 (1, Istodax, romidepsin) in a murine hollow fiber assay consisting of 12 implanted tumor cell lines. Spiruchostatin C (2) showed good activity toward LOX IMVI melanoma cells and NCI-H522 non small cell lung cancer cells. Overall, however, FK228 (1) showed a superior in vivo antitumor profile in comparison to the new compound.
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| 21968500 |
Solution structure of a novel α-conotoxin with a distinctive loop spacing pattern |
10.1007/s00726-011-1093-x. |
Amino Acids |
Solution structure of a novel α-conotoxin with a distinctive loop spacing pattern
Abstract
- α-Pharmacological conotoxins are among the most selective ligands of nicotinic acetylcholine receptors with typical cysteine frameworks. They are characterized by the intercysteine loop and classified into various subfamilies, such as α3/5 and α4/7 conotoxins. A novel α-conotoxin, Pu14a (DCPPHPVPGMHKCVCLKTC), with a distinct loop spacing pattern between cysteines was reported recently. Pu14a belongs to the Cys framework 14 (-C-C-C-C) family containing four proline residues in the loop 1 region. Similar to another framework 14 conotoxin Lt14a (MCPPLCKPSCTNC-NH2), Pu14a has C1-C3/C2-C4 disulfide linkage, and can inhibit some subtypes of nicotinic acetylcholine receptors. In this study, the solution structure of Pu14a was investigated using 1H nuclear magnetic resonance spectroscopy to understand the structure-activity relationship of this conotoxin. 20 converged structures of this conopeptide, with RMSD value of 0.77 Å, were obtained based on distance constraints, dihedral angles and disulfide bond constraints. The three-dimensional structure of Pu14a showed remarkable difference from typical α-conotoxins because of a large intercysteine loop between C2 and C13, as well as a 3(10)-helix near the C-terminal. Furthermore, four proline residues in Pu14a adopted the trans conformation that may correlate with the large loop configuration and the biological activity of this conopeptide. The distinct structural characteristics of Pu14a will be very useful for studying the structure-activity relationship of α-conotoxins.
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| 21969609 |
Proteogenomic analysis of Mycobacterium tuberculosis by high resolution mass spectrometry |
10.1074/mcp.M111.011445 |
Molecular & cellular proteomics : MCP |
Proteogenomic analysis of Mycobacterium tuberculosis by high resolution mass spectrometry
Abstract
- The genome sequencing of H37Rv strain of Mycobacterium tuberculosis was completed in 1998 followed by the whole genome sequencing of a clinical isolate, CDC1551 in 2002. Since then, the genomic sequences of a number of other strains have become available making it one of the better studied pathogenic bacterial species at the genomic level. However, annotation of its genome remains challenging because of high GC content and dissimilarity to other model prokaryotes. To this end, we carried out an in-depth proteogenomic analysis of the M. tuberculosis H37Rv strain using Fourier transform mass spectrometry with high resolution at both MS and tandem MS levels. In all, we identified 3176 proteins from Mycobacterium tuberculosis representing ~80% of its total predicted gene count. In addition to protein database search, we carried out a genome database search, which led to identification of ~250 novel peptides. Based on these novel genome search-specific peptides, we discovered 41 novel protein coding genes in the H37Rv genome. Using peptide evidence and alternative gene prediction tools, we also corrected 79 gene models. Finally, mass spectrometric data from N terminus-derived peptides confirmed 727 existing annotations for translational start sites while correcting those for 33 proteins. We report creation of a high confidence set of protein coding regions in Mycobacterium tuberculosis genome obtained by high resolution tandem mass-spectrometry at both precursor and fragment detection steps for the first time. This proteogenomic approach should be generally applicable to other organisms whose genomes have already been sequenced for obtaining a more accurate catalogue of protein-coding genes.
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| 21979955 |
Discovery of a linear cyclotide from the bracelet subfamily and its disulfide mapping by top-down mass spectrometry |
10.1074/jbc.M111.290296. |
J Biol Chem |
Discovery of a linear cyclotide from the bracelet subfamily and its disulfide mapping by top-down mass spectrometry
Abstract
- Cyclotides are heat-stable macrocyclic peptides from plants that display a wide range of biological activities. They can be divided into two subfamilies: Möbius or bracelet, based on the presence or absence of a cis-proline residue in loop 5, respectively. Currently, over 150 cyclotides have been discovered, but only four linear variants of the Möbius subfamily have been hitherto isolated. In this study, we report the discovery of two novel cyclotides, hedyotide B1 and hedyotide B2, from the aerial parts of Hedyotis biflora. Hedyotide B1 has a cyclic cystine knot structure typical of cyclotides. Interestingly, hedyotide B2 possesses a linear backbone and is the first linear representative of the bracelet subfamily. Disulfide mapping of hedyotide B2 by a top-down MS/MS approach showed that it shares the same knotted disulfide arrangement as conventional cyclotides. Its unfolding pathway also showed that the penetrating disulfide bond Cys III-VI is the most stable disulfide linkage. Cloning of the gene encoding hedyotide B2 revealed a nonsense mutation that introduces a premature stop codon at the conserved Asn residue position, which is essential for an end-to-end backbone ligation. Biophysical characterization showed that hedyotide B2 was more susceptible to exopeptidase degradation as compared with hedyotide B1. Hedyotide B2 was also inactive against all four tested bacterial strains, whereas hedyotide B1 was bactericidal to Escherichia coli and Streptococcus salivarius at low micromolar concentration. Our results provide a deeper understanding of the structures, functions, and biosynthetic processing of cyclotides and uncyclotides in plants.
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| 21985013 |
A bisamide and four diketopiperazines from a marine-derived Streptomyces sp |
10.1080/10286020.2011.617744. |
J Asian Nat Prod Res |
A bisamide and four diketopiperazines from a marine-derived Streptomyces sp
Abstract
- A new bisamide N₁-acetyl-N₇-phenylacetyl cadaverine (1) and a series of diketopiperazines including a new diketopiperazine cyclo(2-hydroxy-Pro-R-Leu) (2), together with a new natural product cyclo(4-hydroxy-S-Pro-S-Trp) (3) and two known leucine-based diketopiperazines cyclo(4-hydroxy-R-Pro-S-Leu) (4) and cyclo (S-Pro-R-Leu) (5), were isolated from ethyl acetate extract of a fermentation broth of a marine-derived Streptomyces sp. Their structures were elucidated by the interpretation of spectroscopic analysis. The antitumor activities of compounds 1-3 against HL-60 cell lines were tested by MTT assay.
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| 21994939 |
Polyubiquitination of insulin-like growth factor I receptor (IGF-IR) activation loop promotes antibody-induced receptor internalization and down-regulation |
10.1074/jbc.M111.288514. |
J Biol Chem |
Polyubiquitination of insulin-like growth factor I receptor (IGF-IR) activation loop promotes antibody-induced receptor internalization and down-regulation
Abstract
- Ubiquitination has been implicated in negatively regulating insulin-like growth factor I receptor (IGF-IR) activity. Because of the relative stability of IGF-IR in the presence of ligand stimulation, IGF-IR ubiquitination sites have yet to be mapped and characterized, thus preventing a direct demonstration of how the receptor ubiquitination contributes to downstream molecular cascades. We took advantage of an anti-IGF-IR antibody (h10H5) that induces more efficient receptor down-regulation to show that IGF-IR is promptly and robustly ubiquitinated. The ubiquitination sites were mapped to the two lysine residues in the IGF-IR activation loop (Lys-1138 and Lys-1141) and consisted of polyubiquitin chains formed through both Lys-48 and Lys-29 linkages. Mutation of these ubiquitinated lysine residues resulted in decreased h10H5-induced IGF-IR internalization and down-regulation as well as a reduced cellular response to h10H5 treatment. We have therefore demonstrated that IGF-IR ubiquitination contributes critically to the down-regulating and antiproliferative activity of h10H5. This finding is physiologically relevant because insulin-like growth factor I appears to mediate ubiquitination of the same major sites as h10H5 (albeit to a lesser extent), and ubiquitination is facilitated by pre-existing phosphorylation of the receptor in both cases. Furthermore, identification of a breast cancer cell line with a defect in IGF-IR ubiquitination suggests that this could be an important tumor resistance mechanism to evade down-regulation-mediated negative regulation of IGF-IR activity in cancer.
|
| 22027826 |
ACAP4 protein cooperates with Grb2 protein to orchestrate epidermal growth factor-stimulated integrin β1 recycling in cell migration |
10.1074/jbc.M111.278770. |
J Biol Chem |
ACAP4 protein cooperates with Grb2 protein to orchestrate epidermal growth factor-stimulated integrin β1 recycling in cell migration
Abstract
- ARF6 GTPase is an important regulator of membrane trafficking and actin-based cytoskeleton dynamics active at the leading edge of migrating cells. The integrin family heterodimeric transmembrane proteins serve as major receptors for extracellular matrix proteins, which play essential roles in cell adhesion and migration. Our recent proteomic analyses of ARF6 effectors have identified a novel ARF6 GTPase-activating protein, ACAP4, essential for EGF-induced cell migration. However, molecular mechanisms underlying ACAP4-mediated cell migration have remained elusive. Here, we show that ACAP4 regulates integrin β1 dynamics during EGF-stimulated cell migration by interaction with Grb2. Our biochemical study shows that EGF stimulation induces phosphorylation of tyrosine 733, which enables ACAP4 to bind Grb2. This interaction of ACAP4 with Grb2 regulates integrin β1 recycling to the plasma membrane. Importantly, knockdown of ACAP4 by siRNA or overexpression of ACAP4 decreased recycling of integrin β1 to the plasma membrane and reduced integrin-mediated cell migration. Taken together, these results suggest a novel function for ACAP4 in the regulation of cell migration through controlling integrin β1 dynamics.
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| 22028381 |
Quantitative detection of single amino acid polymorphisms by targeted proteomics |
10.1093/jmcb/mjr024. |
J Mol Cell Biol |
Quantitative detection of single amino acid polymorphisms by targeted proteomics
Abstract
- Single-nucleotide polymorphisms (SNPs) are recognized as one kind of major genetic variants in population scale. However, polymorphisms at the proteome level in population scale remain elusive. In the present study, we named amino acid variances derived from SNPs within coding regions as single amino acid polymorphisms (SAPs) at the proteome level, and developed a pipeline of non-targeted and targeted proteomics to identify and quantify SAP peptides in human plasma. The absolute concentrations of three selected SAP-peptide pairs among 290 Asian individuals were measured by selected reaction monitoring (SRM) approach, and their associations with both obesity and diabetes were further analyzed. This work revealed that heterozygotes and homozygotes with various SAPs in a population could have different associations with particular traits. In addition, the SRM approach allows us for the first time to separately measure the absolute concentration of each SAP peptide in the heterozygotes, which also shows different associations with particular traits.
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| 22029824 |
Extremely abundant antimicrobial peptides existed in the skins of nine kinds of Chinese odorous frogs |
10.1021/pr200782u. |
J Proteome Res |
Extremely abundant antimicrobial peptides existed in the skins of nine kinds of Chinese odorous frogs
Abstract
- Peptide agents are regarded as hopeful candidates to solve life-threatening resistance of pathogenic microorganisms to classic antibiotics due to their unique action mechanisms. Peptidomic and genomic investigation of natural antimicrobial peptides (AMPs) from amphibian skin secretions can provide a large amount of structure-functional information to design peptide antibiotics with therapeutic potential. In the present study, we identified a large number of AMPs from the skins of nine kinds of Chinese odorous frogs. Eighty AMPs were purified from three different odorous frogs and confirmed by peptidomic analysis. Our results indicated that post-translational modification of AMPs rarely happened in odorous frogs. cDNAs encoding precursors of 728 AMPs, including all the precursors of the confirmed 80 native peptides, were cloned from the constructed AMP cDNA libraries of nine Chinese odorous frogs. On the basis of the sequence similarity of deduced mature peptides, these 728 AMPs were grouped into 97 different families in which 71 novel families were identified. Out of these 728 AMPs, 662 AMPs were novel and 28 AMPs were reported previously in other frog species. Our results revealed that identical AMPs were widely distributed in odorous frogs; 49 presently identified AMPs could find their identical molecules in different amphibian species. Purified peptides showed strong antimicrobial activities against 4 tested microbe strains. Twenty-three deduced peptides were synthesized and their bioactivities, including antimicrobial, antioxidant, hemolytic, immunomodulatory and insulin-releasing activities, were evaluated. Our findings demonstrate the extreme diversity of AMPs in amphibian skins and provide plenty of templates to develop novel peptide antibiotics.
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| 22036992 |
Diabetic nephropathy-related active cyclic peptides from the roots of Brachystemma calycinum |
10.1016/j.bmcl.2011.10.004. |
Bioorg Med Chem Lett |
Diabetic nephropathy-related active cyclic peptides from the roots of Brachystemma calycinum
Abstract
- Three new cyclic peptides, namely duanbanhuains A-C (1-3), were isolated from the roots of Brachystemma calycinum which is a traditional medicine used to treat rheumatic diseases. Their structures were identified by means of a suite of MS and NMR experiments. These compounds were purposely evaluated for their inhibitory effects on the release of MCP-1, IL-6, collagen IV and reactive oxygen species (ROS) against high-glucose-stimulated mesangial cells. The results showed that compounds 1 and 2 exhibited potent inhibition on the production of IL-6, collagen IV and ROS at the concentration of 10 μM.
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| 22038181 |
Lasiocepsin, a novel cyclic antimicrobial peptide from the venom of eusocial bee Lasioglossum laticeps (Hymenoptera: Halictidae) |
10.1007/s00726-011-1125-6. |
Amino Acids |
Lasiocepsin, a novel cyclic antimicrobial peptide from the venom of eusocial bee Lasioglossum laticeps (Hymenoptera: Halictidae)
Abstract
- In the venom of eusocial bee Lasioglossum laticeps, we identified a novel unique antimicrobial peptide named lasiocepsin consisting of 27 amino acid residues and two disulfide bridges. After identifying its primary structure, we synthesized lasiocepsin by solid-phase peptide synthesis using two different approaches for oxidative folding. The oxidative folding of fully deprotected linear peptide resulted in a mixture of three products differing in the pattern of disulfide bridges. Regioselective disulfide bond formation significantly improved the yield of desired product. The synthetic lasiocepsin possessed antimicrobial activity against both Gram-positive and -negative bacteria, antifungal activity against Candida albicans, and no hemolytic activity against human erythrocytes. We synthesized two lasiocepsin analogs cyclized through one native disulfide bridge in different positions and having the remaining two cysteines substituted by alanines. The analog cyclized through a Cys8-Cys25 disulfide bridge showed reduced antimicrobial activity compared to the native peptide while the second one (Cys17-Cys27) was almost inactive. Linear lasiocepsin having all four cysteine residues substituted by alanines or alkylated was also inactive. That was in contrast to the linear lasiocepsin with all four cysteine residues non-paired, which exhibited remarkable antimicrobial activity. The shortening of lasiocepsin by several amino acid residues either from the N- or C-terminal resulted in significant loss of antimicrobial activity. Study of Bacillus subtilis cells treated by lasiocepsin using transmission electron microscopy showed leakage of bacterial content mainly from the holes localized at the ends of the bacterial cells.
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| 22039263 |
Engineering pro-angiogenic peptides using stable, disulfide-rich cyclic scaffolds |
10.1182/blood-2011-06-359141. |
Blood |
Engineering pro-angiogenic peptides using stable, disulfide-rich cyclic scaffolds
Abstract
- Fragments from the extracellular matrix proteins laminin and osteopontin and a sequence from VEGF have potent proangiogenic activity despite their small size (< 10 residues). However, these linear peptides have limited potential as drug candidates for therapeutic angiogenesis because of their poor stability. In the present study, we show that the therapeutic potential of these peptides can be significantly improved by "grafting" them into cyclic peptide scaffolds. Momordica cochinchinensis trypsin inhibitor-II (MCoTI-II) and sunflower trypsin inhibitor-1 (SFTI-1), naturally occurring, plant-derived cyclic peptides of 34 and 14 residues, respectively, were used as scaffolds in this study. Using this approach, we have designed a peptide that, in contrast to the small peptide fragments, is stable in human serum and at nanomolar concentration induces angiogenesis in vivo. This is the first report of using these scaffolds to improve the activity and stability of angiogenic peptide sequences and is a promising approach for promoting angiogenesis for therapeutic uses.
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