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排序方式: 共有319条查询结果,搜索用时 15 毫秒
191.
Beckmann S Hahnel S Cailliau K Vanderstraete M Browaeys E Dissous C Grevelding CG 《The Journal of biological chemistry》2011,286(49):42325-42336
Cellular protein-tyrosine kinases play key roles in signal transduction processes in eukaryotes. SmTK4 was the first Syk kinase identified in a parasite and found to be tissue-specifically transcribed in the gonads of adult Schistosoma mansoni. Functional analyses confirmed its role in oogenesis and spermatogenesis. As an SmTK4 upstream binding partner, the cellular protein-tyrosine kinase SmTK6 was isolated from a yeast two-hybrid library. Phylogenetic analyses performed in this study confirmed the first suggestions of a hybrid character of SmTK6. Biochemical studies made in Xenopus oocytes using inhibitors against Src (herbimycin A) and Abl (imatinib) kinases exhibited a biochemical inhibition profile of SmTK6, which was intermediate of Src and Abl kinases. As SmTK6 upstream interaction partners, we identified among others the known Src kinase SmTK3 and the Venus kinase receptor SmVKR1 of S. mansoni by yeast two-hybrid analyses, all of which co-localized in the gonads. Co-immunoprecipitation experiments confirmed interactions between SmTK6 and SmTK3 or SmVKR1. In Xenopus oocytes, it was finally shown that SmVKR1 but also SmTK3 were able to activate SmTK6 enzymatic activity indicating its functions in a receptor tyrosine kinase signal transduction cascade. These results not only demonstrate an intermediate but Src-biased profile of the unusual kinase SmTK6. They also strongly substantiate previous indications for a kinase complex, consisting of a receptor tyrosine kinase, Syk and Src kinases, which has been hypothesized to be involved in proliferation and differentiation processes in the gonads of schistosomes. 相似文献
192.
Margot J. Zaccardi Kathleen F. O'Rourke Eric M. Yezdimer Laura J. Loggia Svenja Woldt David D. Boehr 《Protein science : a publication of the Protein Society》2014,23(3):302-311
Substrate binding, product release, and likely chemical catalysis in the tryptophan biosynthetic enzyme indole‐3‐glycerol phosphate synthase (IGPS) are dependent on the structural dynamics of the β1α1 active‐site loop. Statistical coupling analysis and molecular dynamic simulations had previously indicated that covarying residues in the β1α1 and β2α2 loops, corresponding to Arg54 and Asn90, respectively, in the Sulfolobus sulfataricus enzyme (ssIGPS), are likely important for coordinating functional motions of these loops. To test this hypothesis, we characterized site mutants at these positions for changes in catalytic function, protein stability and structural dynamics for the thermophilic ssIGPS enzyme. Although there were only modest changes in the overall steady‐state kinetic parameters, solvent viscosity and solvent deuterium kinetic isotope effects indicated that these amino acid substitutions change the identity of the rate‐determining step across multiple temperatures. Surprisingly, the N90A substitution had a dramatic effect on the general acid/base catalysis of the dehydration step, as indicated by the loss of the descending limb in the pH rate profile, which we had previously assigned to Lys53 on the β1α1 loop. These changes in enzyme function are accompanied with a quenching of ps‐ns and µs‐ms timescale motions in the β1α1 loop as measured by nuclear magnetic resonance studies. Altogether, our studies provide structural, dynamic and functional rationales for the coevolution of residues on the β1α1 and β2α2 loops, and highlight the multiple roles that the β1α1 loop plays in IGPS catalysis. Thus, substitution of covarying residues in the active‐site β1α1 and β2α2 loops of indole‐3‐glycerol phosphate synthase results in functional, structural, and dynamic changes, highlighting the multiple roles that the β1α1 loop plays in enzyme catalysis and the importance of regulating the structural dynamics of this loop through noncovalent interactions with nearby structural elements. 相似文献
193.
Hydrogenase-independent uptake and metabolism of electrons by the archaeon Methanococcus maripaludis
Svenja T Lohner J?rg S Deutzmann Bruce E Logan John Leigh Alfred M Spormann 《The ISME journal》2014,8(8):1673-1681
Direct, shuttle-free uptake of extracellular, cathode-derived electrons has been postulated as a novel mechanism of electron metabolism in some prokaryotes that may also be involved in syntrophic electron transport between two microorganisms. Experimental proof for direct uptake of cathodic electrons has been mostly indirect and has been based on the absence of detectable concentrations of molecular hydrogen. However, hydrogen can be formed as a transient intermediate abiotically at low cathodic potentials (<−414 mV) under conditions of electromethanogenesis. Here we provide genetic evidence for hydrogen-independent uptake of extracellular electrons. Methane formation from cathodic electrons was observed in a wild-type strain of the methanogenic archaeon Methanococcus maripaludis as well as in a hydrogenase-deletion mutant lacking all catabolic hydrogenases, indicating the presence of a hydrogenase-independent mechanism of electron catabolism. In addition, we discovered a new route for hydrogen or formate production from cathodic electrons: Upon chemical inhibition of methanogenesis with 2-bromo-ethane sulfonate, hydrogen or formate accumulated in the bioelectrochemical cells instead of methane. These results have implications for our understanding on the diversity of microbial electron uptake and metabolism. 相似文献
194.
Maria Trott Svenja Wei? Sascha Antoni Joachim Koch Hagen von Briesen Michael Hust Ursula Dietrich 《PloS one》2014,9(5)
HIV neutralizing antibodies (nAbs) represent an important tool in view of prophylactic and therapeutic applications for HIV-1 infection. Patients chronically infected by HIV-1 represent a valuable source for nAbs. HIV controllers, including long-term non-progressors (LTNP) and elite controllers (EC), represent an interesting subgroup in this regard, as here nAbs can develop over time in a rather healthy immune system and in the absence of any therapeutic selection pressure. In this study, we characterized two particular antibodies that were selected as scFv antibody fragments from a phage immune library generated from an LTNP with HIV neutralizing antibodies in his plasma. The phage library was screened on recombinant soluble gp140 envelope (Env) proteins. Sequencing the selected peptide inserts revealed two major classes of antibody sequences. Binding analysis of the corresponding scFv-Fc derivatives to various trimeric and monomeric Env constructs as well as to peptide arrays showed that one class, represented by monoclonal antibody (mAb) A2, specifically recognizes an epitope localized in the pocket binding domain of the C heptad repeat (CHR) in the ectodomain of gp41, but only in the trimeric context. Thus, this antibody represents an interesting tool for trimer identification. MAb A7, representing the second class, binds to structural elements of the third variable loop V3 and neutralizes tier 1 and tier 2 HIV-1 isolates of different subtypes with matching critical amino acids in the linear epitope sequence. In conclusion, HIV controllers are a valuable source for the selection of functionally interesting antibodies that can be selected on soluble gp140 proteins with properties from the native envelope spike. 相似文献
195.
Emilia Daniłowicz-Luebert Svenja Steinfelder Anja A. Kühl Gennadiy Drozdenko Richard Lucius Margitta Worm Eckard Hamelmann Susanne Hartmann 《International journal for parasitology》2013,43(3-4):201-210
Helminth parasites modulate the immune system by complex mechanisms to ensure persistence in the host. Released immunomodulatory parasite components lead to a beneficial environment for the parasite by targeting different host cells and in parallel to a modulation of unrelated inflammatory responses in the host, such as allergy. The aim of this study was to investigate the effect of the potent helminth immunomodulator, filarial cystatin, in a murine model of airway inflammation and hyperreactivity induced by a clinically relevant aeroallergen (timothy grass (Phleum pratense) pollen) and on the function of peripheral blood mononuclear cells (PBMCs) from timothy grass pollen allergic patients. BALB/c mice were systemically sensitised with a recombinant major allergen of timothy grass pollen (rPhl p 5b) and then challenged with timothy grass pollen extract (GPE) via the airways. Filarial cystatin was applied i.p. during the sensitisation phase. Airway hyperresponsiveness to methacholine challenges, inflammation of airways, inflammatory cell recruitment, cytokine production and lung histopathology were investigated. In a translational approach, PBMCs from allergic subjects and healthy controls were treated in vitro with cystatin prior to stimulation with GPE. Administration of filarial cystatin suppressed rPhl p 5b-induced allergen-specific Th2-responses and airway inflammation, inhibited local recruitment of eosinophils, reduced levels of allergen-specific IgE and down-regulated IL-5 and IL-13 in the bronchoalveolar lavage (BAL). Ex vivo restimulation with cystatin of spleen cells from cystatin-treated mice induced the production of IL-10, while cystatin inhibited allergen-specific IL-5 and IL-13 levels. Human PBMCs from timothy grass pollen allergic patients displayed a shift towards a Th1 response after treatment with cystatin. These results show that filarial cystatin ameliorates allergic inflammation and disease in a clinically relevant model of allergy. This data indicate that filarial cystatin has a modulatory effect on grass pollen-specific responses warranting further investigation of potential preventive and therapeutic options in the treatment of allergies. 相似文献
196.
Kathrin Buffen Marije Oosting Svenja Mennens Paras K. Anand Theo S. Plantinga Patrick Sturm Frank L. van de Veerdonk Jos W. M. van der Meer Ramnik J. Xavier Thirumala-Devi Kanneganti Mihai G. Netea Leo A. B. Joosten 《The Journal of biological chemistry》2013,288(12):8658-8666
Borrelia burgdorferi sensu lato is the causative agent of Lyme disease. Recent studies have shown that recognition of the spirochete is mediated by TLR2 and NOD2. The latter receptor has been associated with the induction of the intracellular degradation process called autophagy. The present study demonstrated for the first time the induction of autophagy by exposure to B. burgdorferi and that autophagy modulates the B. burgdorferi-dependent cytokine production. Human peripheral blood mononuclear cells treated with autophagy inhibitors showed an increased IL-1β and IL-6 production in response to the exposure of the spirochete, whereas TNFα production was unchanged. Autophagy induction against B. burgdorferi was dependent on reactive oxygen species (ROS) because cells from patients with chronic granulomatous disease, which are defective in ROS production, also produced elevated IL-1β. Further, the enhanced production of the proinflammatory cytokines was because of the elevated mRNA expression in the absence of autophagy. Our results thus demonstrate the induction of autophagy, which, in turn, modulates cytokine production by B. burgdorferi for the first time. 相似文献
197.
Svenja Sammler Valerio Ketmaier Katja Havenstein Ralph Tiedemann 《Journal of molecular evolution》2013,77(5-6):199-205
Philippine hornbills of the genera Aceros and Penelopides (Bucerotidae) are known to possess a large tandemly duplicated fragment in their mitochondrial genome, whose paralogous parts largely evolve in concert. In the present study, we surveyed the two distinguishable duplicated control regions in several individuals of the Luzon Tarictic Hornbill Penelopides manillae, compare their characteristics within and across individuals, and report on an intraspecific mitochondrial gene rearrangement found in one single specimen, i.e., an interchange between the two control regions. To our knowledge, this is the first observation of two distinct mitochondrial genome rearrangements within a bird species. We briefly discuss a possible evolutionary mechanism responsible for this pattern, and highlight potential implications for the application of control region sequences as a marker in population genetics and phylogeography. 相似文献
198.
Lena Feuerer Susanne Lamm Ingmar Henz Melanie Kappelmann‐Fenzl Sebastian Haferkamp Svenja Meierjohann Claus Hellerbrand Silke Kuphal Anja Katrin Bosserhoff 《Pigment cell & melanoma research》2019,32(6):777-791
The protein melanoma inhibitory activity (MIA) is known to be expressed in melanoma and to support melanoma progression. Interestingly, previous studies also observed the expression of MIA in nevi. Concentrating on these findings, we revealed that MIA expression is correlated with a senescent state in melanocytes. Induction of replicative or oncogene‐induced senescence resulted in increased MIA expression in vitro. Notably, MIA knockdown in senescent melanocytes reduced the percentage of senescence‐associated beta‐Gal‐positive cells and enhanced proliferation. Using the melanoma mouse model Tg(Grm1), MIA‐deficient mice supported the impact of MIA on senescence by showing a significantly earlier tumor onset compared to controls. In melanocytes, MIA knockdown led to a downregulation of the cell cycle inhibitor p21 in vitro and in vivo. In contrast, after induction of hTERT in human melanoma cells, p21 regulation by MIA was lost. In summary, our data show for the first time that MIA is a regulator of cellular senescence in human and murine melanocytes. 相似文献
199.
Benjamin Heidrich Hans-J?rg Cordes Hartwig Klinker Bernd M?ller Uwe Naumann Martin R?ssle Michael R. Kraus Klaus H. B?ker Christoph Roggel Marcus Schuchmann Albrecht Stoehr Andreas Trein Svenja Hardtke Andrea Gonnermann Armin Koch Heiner Wedemeyer Michael P. Manns Markus Cornberg 《PloS one》2015,10(6)
Although sofosbuvir has been approved for patients with genotypes 2/3 (G2/3), many parts of the world still consider pegylated Interferon alpha (P) and ribavirin (R) as standard of care for G2/3. Patients with rapid virological response (RVR) show response rates >80%. However, SVR (sustained virological response) in non-RVR patients is not satisfactory. Longer treatment duration may be required but evidence from prospective trials are lacking. A total of 1006 chronic HCV genotype 2/3 patients treated with P/R were recruited into a German HepNet multicenter screening registry. Of those, only 226 patients were still HCV RNA positive at week 4 (non-RVR). Non-RVR patients with ongoing response after 24 weeks P-2b/R qualified for OPTEX, a randomized trial investigating treatment extension of additional 24 weeks (total 48 weeks, Group A) or additional 12 weeks (total 36 weeks, group B) of 1.5 μg/kg P-2b and 800-1400 mg R. Due to the low number of patients without RVR, the number of 150 anticipated study patients was not met and only 99 non-RVR patients (n=50 Group A, n=49 Group B) could be enrolled into the OPTEX trial. Baseline factors did not differ between groups. Sixteen patients had G2 and 83 patients G3. Based on the ITT (intention-to-treat) analysis, 68% [55%; 81%] in Group A and 57% [43%; 71%] in Group B achieved SVR (p= 0.31). The primary endpoint of better SVR rates in Group A compared to a historical control group (SVR 70%) was not met. In conclusion, approximately 23% of G2/3 patients did not achieve RVR in a real world setting. However, subsequent recruitment in a treatment-extension study was difficult. Prolonged therapy beyond 24 weeks did not result in higher SVR compared to a historical control group.
Trial Registration
ClinicalTrials.gov NCT00803309 相似文献200.
Human ABCG2 is an efflux protein belonging to the ATP-binding cassette transporter superfamily. It is expressed in the plasma
membrane of different cell types performing various physiological functions. It is the most recently discovered MDR transporter
and its structure and function are still not well understood. Thus, expression and functional reconstitution of the protein
in different variants and from different sources are important steps for its further investigation. In this work we describe
a recombinant synthesis of human ABCG2 R482G from S. cerevisiae. We expressed the human ABCG2 R482G variant in S. cerevisiae and purified the protein from total yeast membranes. Using a panel of sixteen detergents, we analyzed the efficiency of extraction
of ABCG2 from membranes by SDS–PAGE and immunoblot analysis. Based on these results, three detergents were selected for further
purification studies and two of them, n-octyl-β-D-glucopyranoside and n-dodecyl-β-D-maltopyranoside, yielded functional protein
after reconstitution into liposomes. We show here the first example of purified and reconstituted ABCG2 expressed in S. cerevisiae retaining drug-stimulated ATPase activity. 相似文献