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41.
Mosses have substantial amounts of long chain C20 polyunsaturated fatty acids, such as arachidonic and eicosapentaenoic acid, in addition to the shorter chain C18 α-linolenic and linoleic acids, which are typical substrates of lipoxygenases in flowering plants. To identify the fatty acid substrates used by moss lipoxygenases, eight lipoxygenase genes from Physcomitrella patens were heterologously expressed in Escherichia coli, and then analyzed for lipoxygenase activity using linoleic, α-linolenic and arachidonic acids as substrates. Among the eight moss lipoxygenases, only seven were found to be enzymatically active in vitro, two of which selectively used arachidonic acid as the substrate, while the other five preferred α-linolenic acid. Based on enzyme assays using a Clark-type oxygen electrode, all of the active lipoxygenases had an optimum pH at 7.0, except for one with highest activity at pH 5.0. HPLC analyses indicated that the two arachidonic acid lipoxygenases form (12S)-hydroperoxy eicosatetraenoic acid as the main product, while the other five lipoxygenases produce mainly (13S)-hydroperoxy octadecatrienoic acid from α-linolenic acid. These results suggest that mosses may have both C20 and C18 based oxylipin pathways. 相似文献
42.
1. Inputs of animal and plant detritus are the main energy sources for food webs in a number of isolated container systems, including discarded automobile tyres and tree holes. Containers are dominated by mosquitoes in the genera Culex and Aedes, which among other differences often engage in different foraging behaviours. We hypothesised that because Aedes feed more by browsing surfaces, whereas Culex often filter the water column, these mosquitoes would show variation in performance and differentially affect detritus. Effects of different ratios of animal and plant detritus on survival, mass, and development time for two common container mosquito species, Culex restuans L. and Aedes albopictus Skuse, were examined. We also quantified detrital contribution to biomass via isotopic and nutrient analysis and the effect of larvae on detrital decay. 2. Adult male and female mass of both species was highest with some animal detritus and lowest in only leaf detritus. Aedes albopictus survival was higher than C. restuans across most detritus ratios. 3. Aedes albopictus had higher values of 15N and in some cases 13C across all detritus ratios compared with C. restuans; A. albopictus had lower nitrogen in tissue. Aedes albopictus appeared to be more efficient at obtaining potentially limiting nutrients and had a greater overall effect on detrital decay – a possible consequence of greater foraging effort. 4. Findings further support the view that mosquito performance can be influenced by detritus type, and provide a more precise hypothesis (i.e. lower need for nitrogen) that may explain the superior competitive ability of A. albopictus over other container mosquitoes. 相似文献
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44.
Liza Cubeddu Catherine X. Moss James D. Swarbrick Andrew A. Gooley Keith L. Williams Paul M. G. Curmi Martin B. Slade Bridget C. Mabbutt 《Protein expression and purification》2000,19(3):335
The advantages of the organism Dictyostelium discoideum as an expression host for recombinant glycoproteins have been exploited for the production of an isotopically labeled cell surface protein for NMR structure studies. Growth medium containing [15N]NH4Cl and [13C]glycerol was used to generate isotopically labeled Escherichia coli, which was subsequently introduced to D. discoideum cells in simple Mes buffer. A variety of growth conditions were screened to establish minimal amounts of nitrogen and carbon metabolites for a cost-effective protocol. Following single-step purification by anion-exchange chromatography, 8 mg of uniformly 13C,15N-labeled protein secreted by approximately 1010D. discoideum cells was isolated from 3.3 liters of supernatant. Mass spectrometry showed the recombinant protein of 16 kDa to have incorporated greater than 99.9% isotopic label. The two-dimensional 1H-13C HSQC spectrum confirms 13C labeling of both glycan and amino acid residues of the glycoprotein. All heteronuclear NMR spectra showed a good dispersion of cross-peaks essential for high-quality structure determination. 相似文献
45.
Shen Wang Cong Ma Shen Wang Ucheor B Choi Jihong Gong Xiaoyu Yang Yun Li Austin L Wang Xiaofei Yang Axel T Brunger Cong Ma 《The EMBO journal》2017,36(6):816-829
The soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein syntaxin-1 adopts a closed conformation when bound to Munc18-1, preventing binding to synaptobrevin-2 and SNAP-25 to form the ternary SNARE complex. Although it is known that the MUN domain of Munc13-1 catalyzes the transition from the Munc18-1/syntaxin-1 complex to the SNARE complex, the molecular mechanism is unclear. Here, we identified two conserved residues (R151, I155) in the syntaxin-1 linker region as key sites for the MUN domain interaction. This interaction is essential for SNARE complex formation in vitro and synaptic vesicle priming in neuronal cultures. Moreover, this interaction is important for a tripartite Munc18-1/syntaxin-1/MUN complex, in which syntaxin-1 still adopts a closed conformation tightly bound to Munc18-1, whereas the syntaxin-1 linker region changes its conformation, similar to that of the LE mutant of syntaxin-1 when bound to Munc18-1. We suggest that the conformational change of the syntaxin-1 linker region induced by Munc13-1 initiates ternary SNARE complex formation in the neuronal system. 相似文献
46.
Rasmus H. Fogh Dick Schipper Rolf Boelens Robert Kaptein 《Journal of biomolecular NMR》1995,5(3):259-270
Summary The 1H, 13C and 15N NMR resonances of serine protease PB92 have been assigned using 3D tripleresonance NMR techniques. With a molecular weight of 27 kDa (269 residues) this protein is one of the largest monomeric proteins assigned so far. The side-chain assignments were based mainly on 3D H(C)CH and 3D (H)CCH COSY and TOCSY experiments. The set of assignments encompasses all backbone carbonyl and CHn carbons, all amide (NH and NH2) nitrogens and 99.2% of the amide and CHn protons. The secondary structure and general topology appear to be identical to those found in the crystal structure of serine protease PB92 [Van der Laan et al. (1992) Protein Eng., 5, 405–411], as judged by chemical shift deviations from random coil values, NH exchange data and analysis of NOEs between backbone NH groups.Abbreviations 2D/3D/4D
two-/three-/four-dimensional
- HSQC
heteronuclear single-quantum coherence
- HMQC
heteronuclear multiple-quantum coherence
- COSY
correlation spectroscopy
- TOCSY
total correlation spectroscopy
- NOE
nuclear Overhauser enhancement (connectivity)
- NOESY
2D NOE spectroscopy
Experiment nomenclature (H(C)CH, etc.) follows the conventions used elsewhere [e.g. Ikura et al. (1990) Biochemistry, 29, 4659–4667]. 相似文献
47.
Carbon and nitrogen isotope ratios in different compartments of a healthy and a declining Picea abies forest in the Fichtelgebirge,NE Bavaria 总被引:4,自引:0,他引:4
Summary Natural carbon and nitrogen isotope ratios were measured in different compartments (needles and twigs of different ages and crown positions, litter, understorey vegetation, roots and soils of different horizons) on 5 plots of a healthy and on 8 plots of a declining Norway spruce (Picea abies (L.) Karst.) forest in the Fichtelgebirge (NE Bavaria, Germany), which has recently been described in detail (Oren et al. 1988a; Schulze et al. 1989). The 13C values of needles did not differ between sites or change consistently with needle age, but did decrease from the sun-to the shade-crown. This result confirms earlier conclusions from gas exchange measurements that gaseous air pollutants did no long-lasting damage in an area where such damage was expected. Twigs (13C between-25.3 and-27.8) were significantly less depleted in 13C than needles (13C between-27.3 and-29.1), and 13C in twigs increased consistently with age. The 15N values of needles ranged between-2.5 and-4.1 and varied according to stand and age. In young needles 15N decreased with needle age, but remained constant or increased in needles that were 2 or 3 years old. Needles from the healthy site were more depleted in 15N than those from the declining site. The difference between sites was greater in old needles than in young ones. This differentiation presumably reflects an earlier onset of nitrogen reallocation in needles of the declining stand. 15N values in twigs were more negative than in needles (-3.5 to-5.2) and showed age- and stand-dependent trends that were similar to the needles. 15N values of roots and soil samples increased at both stands with soil depth from-3.5 in the organic layer to +4 in the mineral soil. The 15N values of roots from the mineral soil were different from those of twigs and needles. Roots from the shallower organic layer had values similar to twigs and needles. Thus, the bulk of the assimilated nitrogen was presumably taken up by the roots from the organic layer. The problem of separation of ammonium or nitrate use by roots from different soil horizons is discussed. 相似文献
48.
《Autophagy》2013,9(6):944-956
During the past 20 years, autophagy signaling has entered the main stage of the cell biological theater. Autophagy represents an intracellular degradation process that is involved in both the bulk recycling of cytoplasmic components and the selective removal of organelles, protein aggregates, or intracellular pathogens. The understanding of autophagy has been greatly facilitated by the characterization of the molecular machinery governing this process. In yeast, initiation of autophagy is controlled by the Atg1 kinase complex, which is composed of the Ser/Thr kinase Atg1, the adaptor protein Atg13, and the ternary complex of Atg17-Atg31-Atg29. In vertebrates, the orthologous ULK1 kinase complex contains the Ser/Thr kinase ULK1 and the accessory proteins ATG13, RB1CC1, and ATG101. Among these components, Atg1/ULK1 have gained major attention in the past, i.e., for the identification of upstream regulatory kinases, the characterization of downstream substrates controlling the autophagic flux, or as a druggable target for the modulation of autophagy. However, accumulating data indicate that the function of Atg13/ATG13 has been likely underestimated so far. In addition to ensuring proper Atg1/ULK1 recruitment and activity, this adaptor molecule has been implicated in ULK1-independent autophagy processes. Furthermore, recent data have identified additional binding partners of Atg13/ATG13 besides the components of the Atg1/ULK1 complex, e.g., Atg8 family proteins or acidic phospholipids. Therefore, in this review we will center the spotlight on Atg13/ATG13 and summarize the role that Atg13/ATG13 assumes in the autophagy stage play. 相似文献
49.
50.
Yuran Ma Shaohua Chen Min Chen Xiang Ren Nandini Patel Wenfeng Liu 《Bioscience, biotechnology, and biochemistry》2020,84(10):2069-2076
ABSTRACT 12-O-tetradecanoylphorbol-13-acetate (TPA), is a major active constituent of the seed oil of Croton tiglium L., has pharmacological activity for the treatment of acute myeloid leukemia patients. Diethyldithiocarbamate (DTC) is a potent inhibitor of NF-κB show activity of anticancer. In this study, we determined the effect of DTC and TPA in combination on HL-60 cells cultured in vitro and in vivo. In this study, we have shown that DTC and TPA synergistically inhibited the growth of HL-60 cells and strongly induced apoptosis in the cells. Mechanistic studies showed that the combined effects of DTC and TPA were associated with a decrease in Bcl-2. The animal experiment showed that the combination of DTC and TPA more potently inhibited the growth of HL-60 tumors than either agent alone. Our results indicate that the administration of TPA and DTC in combination may be an effective strategy for inhibiting the growth of acute myeloid leukemia cells. 相似文献