zur Suche springenzur Navigation springenzum Inhalt springen

Sortieren nach: Erscheinungsjahr Typ der Publikation

Zeige Ergebnisse 1 bis 10 von 11.

Publikation

Paudel, G.; Bilova, T.; Schmidt, R.; Greifenhagen, U.; Berger, R.; Tarakhovskaya, E.; Stöckhardt, S.; Balcke, G. U.; Humbeck, K.; Brandt, W.; Sinz, A.; Vogt, T.; Birkemeyer, C.; Wessjohann, L.; Frolov, A.; Osmotic stress is accompanied by protein glycation in Arabidopsis thaliana J. Exp. Bot. 67, 6283-6295, (2016) DOI: 10.1093/jxb/erw395

Among the environmental alterations accompanying oncoming climate changes, drought is the most important factor influencing crop plant productivity. In plants, water deficit ultimately results in the development of oxidative stress and accumulation of osmolytes (e.g. amino acids and carbohydrates) in all tissues. Up-regulation of sugar biosynthesis in parallel to the increasing overproduction of reactive oxygen species (ROS) might enhance protein glycation, i.e. interaction of carbonyl compounds, reducing sugars and α-dicarbonyls with lysyl and arginyl side-chains yielding early (Amadori and Heyns compounds) and advanced glycation end-products (AGEs). Although the constitutive plant protein glycation patterns were characterized recently, the effects of environmental stress on AGE formation are unknown so far. To fill this gap, we present here a comprehensive in-depth study of the changes in Arabidopsis thaliana advanced glycated proteome related to osmotic stress. A 3 d application of osmotic stress revealed 31 stress-specifically and 12 differentially AGE-modified proteins, representing altogether 56 advanced glycation sites. Based on proteomic and metabolomic results, in combination with biochemical, enzymatic and gene expression analysis, we propose monosaccharide autoxidation as the main stress-related glycation mechanism, and glyoxal as the major glycation agent in plants subjected to drought.
Publikation

Otto, A.; Porzel, A.; Schmidt, J.; Brandt, W.; Wessjohann, L.; Arnold, N.; Structure and Absolute Configuration of Pseudohygrophorones A12 and B12, Alkyl Cyclohexenone Derivatives from Hygrophorus abieticola (Basidiomycetes) J. Nat. Prod. 79, 74-80, (2016) DOI: 10.1021/acs.jnatprod.5b00675

Pseudohygrophorones A(12) (1) and B(12) (2), the first naturally occurring alkyl cyclohexenones from a fungal source, and the recently reported hygrophorone B(12) (3) have been isolated from fruiting bodies of the basidiomycete Hygrophorus abieticola Krieglst. ex Gröger & Bresinsky. Their structures were assigned on the basis of extensive one- and two-dimensional NMR spectroscopic analysis as well as ESI-HRMS measurements. The absolute configuration of the three stereogenic centers in the diastereomeric compounds 1 and 2 was established with the aid of (3)JH,H and (4)JH,H coupling constants, NOE interactions, and conformational analysis in conjunction with quantum chemical CD calculations. It was concluded that pseudohygrophorone A(12) (1) is 4S,5S,6S configured, while pseudohygrophorone B(12) (2) was identified as the C-6 epimer of 1, corresponding to the absolute configuration 4S,5S,6R. In addition, the mass spectrometric fragmentation behavior of 1-3 obtained by the higher energy collisional dissociation method allows a clear distinction between the pseudohygrophorones (1 and 2) and hygrophorone B(12) (3). The isolated compounds 1-3 exhibited pronounced activity against phytopathogenic organisms.
Publikation

Otto, M.; Naumann, C.; Brandt, W.; Wasternack, C.; Hause, B.; Activity Regulation by Heteromerization of Arabidopsis Allene Oxide Cyclase Family Members Plants 5, 3, (2016) DOI: 10.3390/plants5010003

Jasmonates (JAs) are lipid-derived signals in plant stress responses and development. A crucial step in JA biosynthesis is catalyzed by allene oxide cyclase (AOC). Four genes encoding functional AOCs (AOC1, AOC2, AOC3 and AOC4) have been characterized for Arabidopsis thaliana in terms of organ- and tissue-specific expression, mutant phenotypes, promoter activities and initial in vivo protein interaction studies suggesting functional redundancy and diversification, including first hints at enzyme activity control by protein-protein interaction. Here, these analyses were extended by detailed analysis of recombinant proteins produced in Escherichia coli. Treatment of purified AOC2 with SDS at different temperatures, chemical cross-linking experiments and protein structure analysis by molecular modelling approaches were performed. Several salt bridges between monomers and a hydrophobic core within the AOC2 trimer were identified and functionally proven by site-directed mutagenesis. The data obtained showed that AOC2 acts as a trimer. Finally, AOC activity was determined in heteromers formed by pairwise combinations of the four AOC isoforms. The highest activities were found for heteromers containing AOC4 + AOC1 and AOC4 + AOC2, respectively. All data are in line with an enzyme activity control of all four AOCs by heteromerization, thereby supporting a putative fine-tuning in JA formation by various regulatory principles.
Publikation

Kaluđerović, G. N.; Hernández-Corroto, E.; Brandt, W.; Zmejkovski, B. B.; Gómez-Ruiz, S.; Palladium(II) complexes with R2edda-derived ligands J. Coord. Chem. 69, 1337-1345, (2016) DOI: 10.1080/00958972.2016.1168519

Four palladium(II) complexes with R2edda ligands, dichlorido(O,O′-dialkylethylenediamine-N,N′-diacetate)palladium(II) monohydrates, [PdCl2(R2edda)]∙H2O, R = Me, Et, n-Pr, i-Bu, and the new ligand precursor i-Bu2edda∙2HCl∙H2O, O,O′-diisobutylethylenediamine-N,N′-diacetate dihydrochloride monohydrate, were synthesized and characterized by IR, 1H and 13C NMR spectroscopy, and elemental analysis. DFT calculations were performed for the palladium(II) complexes and a high possibility for isomer formation due to stereogenic N ligand atoms was confirmed. Moreover, DFT simulations revealed energetic profile of isomer formation. Computational outcomes are in agreement with spectroscopic instrumental findings, both strongly indicating a non-stereoselective reaction between selected esters and K2[PdCl4], forming isomers.
Publikation

Fobofou, S. A. T.; Franke, K.; Porzel, A.; Brandt, W.; Wessjohann, L. A.; Tricyclic Acylphloroglucinols from Hypericum lanceolatum and Regioselective Synthesis of Selancins A and B J. Nat. Prod. 79, 743-753, (2016) DOI: 10.1021/acs.jnatprod.5b00673

The chemical investigation of the chloroform extract of Hypericum lanceolatum guided by 1H NMR, ESIMS, and TLC profiles led to the isolation of 11 new tricyclic acylphloroglucinol derivatives, named selancins A–I (1–9) and hyperselancins A and B (10 and 11), along with the known compound 3-O-geranylemodin (12), which is described for a Hypericum species for the first time. Compounds 8 and 9 are the first examples of natural products with a 6-acyl-2,2-dimethylchroman-4-one core fused with a dimethylpyran unit. The new compounds 1–9 are rare acylphloroglucinol derivatives with two fused dimethylpyran units. Compounds 10 and 11 are derivatives of polycyclic polyprenylated acylphloroglucinols related to hyperforin, the active component of St. John’s wort. Their structures were elucidated by UV, IR, extensive 1D and 2D NMR experiments, HRESIMS, and comparison with the literature data. The absolute configurations of 5, 8, 10, and 11 were determined by comparing experimental and calculated electronic circular dichroism spectra. Compounds 1 and 2 were synthesized regioselectively in two steps. The cytotoxicity of the crude extract (88% growth inhibition at 50 μg/mL) and of compounds 1–6, 8, 9, and 12 (no significant growth inhibition up to a concentration of 10 mM) against colon (HT-29) and prostate (PC-3) cancer cell lines was determined. No anthelmintic activity was observed for the crude extract.
Publikation

Faden, F.; Ramezani, T.; Mielke, S.; Almudi, I.; Nairz, K.; Froehlich, M. S.; Höckendorff, J.; Brandt, W.; Hoehenwarter, W.; Dohmen, R. J.; Schnittger, A.; Dissmeyer, N.; Phenotypes on demand via switchable target protein degradation in multicellular organisms Nat. Commun. 7, 12202, (2016) DOI: 10.1038/ncomms12202

Phenotypes on-demand generated by controlling activation and accumulation of proteins of interest are invaluable tools to analyse and engineer biological processes. While temperature-sensitive alleles are frequently used as conditional mutants in microorganisms, they are usually difficult to identify in multicellular species. Here we present a versatile and transferable, genetically stable system based on a low-temperature-controlled N-terminal degradation signal (lt-degron) that allows reversible and switch-like tuning of protein levels under physiological conditions in vivo. Thereby, developmental effects can be triggered and phenotypes on demand generated. The lt-degron was established to produce conditional and cell-type-specific phenotypes and is generally applicable in a wide range of organisms, from eukaryotic microorganisms to plants and poikilothermic animals. We have successfully applied this system to control the abundance and function of transcription factors and different enzymes by tunable protein accumulation.
Publikation

Domik, D.; Thürmer, A.; Weise, T.; Brandt, W.; Daniel, R.; Piechulla, B.; A Terpene Synthase Is Involved in the Synthesis of the Volatile Organic Compound Sodorifen of Serratia plymuthica 4Rx13 Front. Microbiol. 7, 737, (2016) DOI: 10.3389/fmicb.2016.00737

Bacteria release a plethora of volatile organic compounds, including compounds with extraordinary structures. Sodorifen (IUPAC name: 1,2,4,5,6,7,8-heptamethyl-3-methylenebicyclo[3.2.1]oct-6-ene) is a recently identified and unusual volatile hydrocarbon that is emitted by the rhizobacterium Serratia plymuthica 4R×13. Sodorifen comprises a bicyclic ring structure solely consisting of carbon and hydrogen atoms, where every carbon atom of the skeleton is substituted with either a methyl or a methylene group. This unusual feature of sodorifen made a prediction of its biosynthetic origin very difficult and so far its biosynthesis is unknown. To unravel the biosynthetic pathway we performed genome and transcriptome analyses to identify candidate genes. One knockout mutant (SOD_c20750) showed the desired negative sodorifen phenotype. Here it was shown for the first time that this gene is indispensable for the synthesis of sodorifen and strongly supports the hypothesis that sodorifen descends from the terpene metabolism. SOD_c20750 is the first bacterial terpene cyclase isolated from Serratia spp. and Enterobacteriales. Homology modeling revealed a 3D structure, which exhibits a functional role of amino acids for intermediate cation stabilization (W325) and putative proton acception (Y332). Moreover, the size and hydrophobicity of the active site strongly indicates that indeed the enzyme may catalyze the unusual compound sodorifen.
Publikation

Dieckow, J.; Brandt, W.; Hattermann, K.; Schob, S.; Schulze, U.; Mentlein, R.; Ackermann, P.; Sel, S.; Paulsen, F. P.; CXCR4 and CXCR7 Mediate TFF3-Induced Cell Migration Independently From the ERK1/2 Signaling Pathway Invest. Ophthalmol. Vis. Sci. 57, 56-65, (2016) DOI: 10.1167/iovs.15-18129

Purpose: Trefoil factor family (TFF) peptides, and in particular TFF3, are characteristic secretory products of mucous epithelia that promote antiapoptosis, epithelial migration, restitution, and wound healing. For a long time, a receptor for TFF3 had not yet been identified. However, the chemokine receptor CXCR4 has been described as a low affinity receptor for TFF2. Additionally, CXCR7, which is able to heterodimerize with CXCR4, has also been discussed as a potential TFF2 receptor. Since there are distinct structural similarities between the three known TFF peptides, this study evaluated whether CXCR4 and CXCR7 may also act as putative TFF3 receptors.Methods: We evaluated the expression of both CXCR4 and CXCR7 in samples of human ocular surface tissues and cell lines, using RT-PCR, immunohistochemistry, and Western blot analysis. Furthermore, we studied possible binding interactions between TFF3 and the receptor proteins in an x-ray structure-based modeling system. Functional studies of TFF3–CXCR4/CXCR7 interaction were accomplished by cell culture–based migration assays, flow cytometry, and evaluation of activation of the mitogen-activated protein (MAP) kinase signaling cascade.Results: We detected both receptors at mRNA and protein level in all analyzed ocular surface tissues, and in lesser amount in ocular surface cell lines. X-ray structure-based modeling revealed CXCR4 and CXCR7 dimers as possible binding partners to TFF3. Cell culture–based assays revealed enhanced cell migration under TFF3 stimulation in a conjunctival epithelial cell line, which was completely suppressed by blocking CXCR4 and/or CXCR7. Flow cytometry showed increased proliferation rates after TFF3 treatment, while blocking both receptors had no effect on this increase. Trefoil factor family 3 also activated the MAP kinase signaling cascade independently from receptor activity.Conclusions: Dimers CXCR4 and CXCR7 are involved in TFF3-dependent activation of cell migration, but not cell proliferation. The ERK1/2 pathway is activated in the process, but not influenced by CXCR4 or CXCR7. These results implicate a dependence of TFF3 activity as to cell migration on the chemokine receptors CXCR4 and CXCR7 at the ocular surface.
Publikation

Weigl, S.; Brandt, W.; Langhammer, R.; Roos, W.; The Vacuolar Proton-Cation Exchanger EcNHX1 Generates pH Signals for the Expression of Secondary Metabolism in Eschscholzia californica Plant Physiol. 170, 1135-1148, (2016) DOI: 10.1104/pp.15.01570

Cell cultures of Eschscholzia californica react to a fungal elicitor by the overproduction of antimicrobial benzophenanthridine alkaloids. The signal cascade toward the expression of biosynthetic enzymes includes (1) the activation of phospholipase A2 at the plasma membrane, resulting in a peak of lysophosphatidylcholine, and (2) a subsequent, transient efflux of vacuolar protons, resulting in a peak of cytosolic H+. This study demonstrates that one of the Na+/H+ antiporters acting at the tonoplast of E. californica cells mediates this proton flux. Four antiporter-encoding genes were isolated and cloned from complementary DNA (EcNHX1–EcNHX4). RNA interference-based, simultaneous silencing of EcNHX1, EcNHX3, and EcNHX4 resulted in stable cell lines with largely diminished capacities of (1) sodium-dependent efflux of vacuolar protons and (2) elicitor-triggered overproduction of alkaloids. Each of the four EcNHX genes of E. californica reconstituted the lack of Na+-dependent H+ efflux in a Δnhx null mutant of Saccharomyces cerevisiae. Only the yeast strain transformed with and expressing the EcNHX1 gene displayed Na+-dependent proton fluxes that were stimulated by lysophosphatidylcholine, thus giving rise to a net efflux of vacuolar H+. This finding was supported by three-dimensional protein homology models that predict a plausible recognition site for lysophosphatidylcholine only in EcNHX1. We conclude that the EcNHX1 antiporter functions in the elicitor-initiated expression of alkaloid biosynthetic genes by recruiting the vacuolar proton pool for the signaling process.
Publikation

Scheler, U.; Brandt, W.; Porzel, A.; Rothe, K.; Manzano, D.; Božić, D.; Papaefthimiou, D.; Balcke, G. U.; Henning, A.; Lohse, S.; Marillonnet, S.; Kanellis, A. K.; Ferrer, A.; Tissier, A.; Elucidation of the biosynthesis of carnosic acid and its reconstitution in yeast Nat. Commun. 7, 12942, (2016) DOI: 10.1038/ncomms12942

Rosemary extracts containing the phenolic diterpenes carnosic acid and its derivative carnosol are approved food additives used in an increasingly wide range of products to enhance shelf-life, thanks to their high anti-oxidant activity. We describe here the elucidation of the complete biosynthetic pathway of carnosic acid and its reconstitution in yeast cells. Cytochrome P450 oxygenases (CYP76AH22-24) from Rosmarinus officinalis and Salvia fruticosa already characterized as ferruginol synthases are also able to produce 11-hydroxyferruginol. Modelling-based mutagenesis of three amino acids in the related ferruginol synthase (CYP76AH1) from S. miltiorrhiza is sufficient to convert it to a 11-hydroxyferruginol synthase (HFS). The three sequential C20 oxidations for the conversion of 11-hydroxyferruginol to carnosic acid are catalysed by the related CYP76AK6-8. The availability of the genes for the biosynthesis of carnosic acid opens opportunities for the metabolic engineering of phenolic diterpenes, a class of compounds with potent anti-oxidant, anti-inflammatory and anti-tumour activities.
IPB Mainnav Search