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91.
Teira E Reinthaler T Pernthaler A Pernthaler J Herndl GJ 《Applied and environmental microbiology》2004,70(7):4411-4414
The recently developed CARD-FISH protocol was refined for the detection of marine Archaea by replacing the lysozyme permeabilization treatment with proteinase K. This modification resulted in about twofold-higher detection rates for Archaea in deep waters. Using this method in combination with microautoradiography, we found that Archaea are more abundant than Bacteria (42% versus 32% of 4',6'-diamidino-2-phenylindole counts) in the deep waters of the North Atlantic and that a larger fraction of Archaea than of Bacteria takes up l-aspartic acid (19% versus 10%). 相似文献
92.
Sengupta J Nilsson J Gursky R Spahn CM Nissen P Frank J 《Nature structural & molecular biology》2004,11(10):957-962
RACK1 serves as a scaffold protein for a wide range of kinases and membrane-bound receptors. It is a WD-repeat family protein and is predicted to have a beta-propeller architecture with seven blades like a Gbeta protein. Mass spectrometry studies have identified its association with the small subunit of eukaryotic ribosomes and, most recently, it has been shown to regulate initiation by recruiting protein kinase C to the 40S subunit. Here we present the results of a cryo-EM study of the 80S ribosome that positively locate RACK1 on the head region of the 40S subunit, in the immediate vicinity of the mRNA exit channel. One face of RACK1 exposes the WD-repeats as a platform for interactions with kinases and receptors. Using this platform, RACK1 can recruit other proteins to the ribosome. 相似文献
93.
Gwaltney SL O'Connor SJ Nelson LT Sullivan GM Imade H Wang W Hasvold L Li Q Cohen J Gu WZ Tahir SK Bauch J Marsh K Ng SC Frost DJ Zhang H Muchmore S Jakob CG Stoll V Hutchins C Rosenberg SH Sham HL 《Bioorganic & medicinal chemistry letters》2003,13(7):1363-1366
Inhibitors of farnesyltransferase are effective against a variety of tumors in mouse models of cancer. Clinical trials to evaluate these agents in humans are ongoing. In our effort to develop new farnesyltransferase inhibitors, we have discovered bioavailable aryl tetrahydropyridines that are potent in cell culture. The design, synthesis, SAR and biological properties of these compounds will be discussed. 相似文献
94.
Laursen BS Siwanowicz I Larigauderie G Hedegaard J Ito K Nakamura Y Kenney JM Mortensen KK Sperling-Petersen HU 《Journal of molecular biology》2003,326(2):543-551
The infB gene encodes translation initiation factor IF2. We have determined the entire sequence of infB from two cold-sensitive Escherichia coli strains IQ489 and IQ490. These two strains have been isolated as suppressor strains for the temperature-sensitive secretion mutation secY24. The mutations causing the suppression phenotype are located within infB. The only variations from the wild-type (wt) infB found in the two mutant strains are a replacement of Asp409 with Glu in strain IQ489 and an insertion of Gly between Ala421 and Gly422 in strain IQ490. Both positions are located in the GTP-binding G-domain of IF2. A model of the G-domain of E.coli IF2 is presented in. Physiological quantities of the recombinant mutant proteins were expressed in vivo in E.coli strains from which the chromosomal infB gene has been inactivated. At 42 degrees C, the mutants sustained normal cell growth, whereas a significant decrease in growth rate was found at 25 degrees C for both mutants as compared to wt IF2 expressed in the control strain. Circular dichroism spectra were recorded of the wt and the two mutant proteins to investigate the structural properties of the proteins. The spectra are characteristic of alpha-helix dominated structure, and reveal a significant different behavior between the wt and mutant IF2s with respect to temperature-induced conformational changes. The temperature-induced conformational change of the wt IF2 is a two-state process. In a ribosome-dependent GTPase assay in vitro the two mutants showed practically no activity at temperatures below 10 degrees C and a reduced activity at all temperatures up to 45 degrees C, as compared to wt IF2. The results indicate that the amino acid residues, Asp409 and Gly422, are located in important regions of the IF2 G-domain and demonstrate the importance of GTP hydrolysis in translation initiation for optimal cell growth. 相似文献
95.
Maier HJ Marienfeld R Wirth T Baumann B 《The Journal of biological chemistry》2003,278(40):39242-39250
In mature B cells RelB-containing complexes are constitutively present in the nucleus, and they are less susceptible to inhibitory kappaB proteins. In most other cell types inhibitory kappaB proteins prevent nuclear translocation and activation of NFkappaB. We reasoned that this characteristic might be because of post-translational modifications of RelB. In Drosophila, signal-dependent phosphorylation of the Rel homologue Dorsal at serine 317 has been shown to be critical for nuclear import. The evolutionary conservation of this serine prompted us to analyze the function of the corresponding site in RelB. As a model system we used the murine S107 plasmacytoma cell line, which lacks endogenous RelB expression. Analysis of S107 cells expressing wild type RelB and serine 368 mutants reveals that serine 368 is not required for nuclear import but that it is critical for RelB dimerization with other members of the NFkappaB family. Similar effects were obtained when the conserved serine in RelA was mutated. We further demonstrate that expression of functional RelB, but not of serine 368 mutants, severely reduces p52 generation and strongly increases expression of the p52 precursor, p100. Wild type RelB, but not mutant RelB, prolonged p100 half-life. We therefore suggest an inhibitory effect of RelB on p100 processing, which is possibly regulated in a signal-dependent manner. 相似文献
96.
Development and validation of a bioreactor for physical stimulation of engineered cartilage 总被引:1,自引:0,他引:1
A bioreactor has been developed to apply different regimes of physical stimulation to tissue specimens under highly controlled conditions. The computer-controlled device exposes specimens to compressive deformation at various strains and frequencies, measures the load applied to each sample and allows simultaneous medium stirring at different velocities. Validation tests confirmed the accuracy of the system in (i) its displacement (errors averaged 0.072+/-0.051 microm), and in (ii) setting the contact with the samples utilizing micrometer screws coupled to plungers (errors averaged 1.74+/-0.36% for samples of 1.60-3.18 mm thickness), thus ensuring accurate compressive deformation. The developed bioreactor, which represents an advance in the technology for physical stimulation of tissue specimens, is currently used to apply compressive deformation and hydrodynamic forces to human chondrocytes cultured in biodegradable polymer scaffolds, with the goals of (i) engineering functional grafts for the repair of cartilage defects (ii). 相似文献
97.
Oscillating perfusion of cell suspensions through three-dimensional scaffolds enhances cell seeding efficiency and uniformity 总被引:13,自引:0,他引:13
We developed a bioreactor for automated cell seeding of three-dimensional scaffolds by continuous perfusion of a cell suspension through the scaffold pores in oscillating directions. Using quantitative biochemical and image analysis techniques, we then evaluated the efficiency and uniformity of perfusion seeding of Polyactive foams as compared to conventional static and spinner flask methods. Finally, we assessed the efficacy of the perfusion seeding technique for different scaffolds and cell types. Perfusion seeding of chondrocytes into Polyactive foams resulted in "viable cell seeding efficiencies," defined as the percentages of initially loaded cells that were seeded and remained viable, that were significantly higher (75 +/- 6%) than those by static (57% +/- 5%) and spinner flask seeding (55% +/- 8%). In addition, as compared to static and spinner flask methods, cells seeded by perfusion were respectively 2.6-fold and 3.8-fold more uniformly distributed and formed more homogeneously sized cell clusters. Chondrocytes seeded by perfusion into Hyaff-11 nonwoven meshes were 26% and 63%, respectively, more uniformly distributed than following static and spinner flask seeding. Bone marrow stromal cells seeded by perfusion into ChronOS porous ceramics were homogeneously distributed throughout the scaffold volume, while following the static method, cells were found only near the top surface of the ceramic. In summary, we demonstrated that our cell seeding perfusion bioreactor generated constructs with remarkably uniform cell distributions at high efficiencies, and was effective for a variety of scaffolds and different mesenchymal cell types. 相似文献
98.
Skirnisdottir S Hreggvidsson GO Holst O Kristjansson JK 《Extremophiles : life under extreme conditions》2001,5(1):45-51
Thermophilic, faculatatively mixotrophic sulfur-oxidizing bacteria were isolated from a sulfide-rich, neutral hot spring in Iceland. The strain, IT-7254, used thiosulfate and elemental sulfur as electron donors, oxygen and nitrate as electron acceptors, and acetate and other organic compounds as carbon sources. After a few days of growth in the presence of thiosulfate, this strain formed sulfur globules. Comparison of intracellular enzymes and heme proteins of heterotrophically and mixotrophically grown cells showed some differences. The new isolate belonged to Thermus scotoductus because the small subunit (SSU) rRNA gene sequence analysis showed 98.6% sequence similarity and 84% DNA:DNA reassociation to Thermus scotoductus NMX2 A. 1. It is also close to Thermus antranikianii HN3-7, with 98.3% and 79% SSU rRNA sequence similarity and DNA:DNA reassociation, respectively. It was also found that both Thermus NMX2 A.1 and T. antranikianii HN3-7 were able to oxidize thiosulfate but that the T. scotoductus type strain SE-1 was not. This is the first report of Thermus strains that are capable of mixotrophic growth with sulfur oxidation. 相似文献
99.
Bacterivorous protists are known to induce changes in bacterial community composition (BCC). We hypothesized that changes
in BCC could be related quantitatively to a measure of grazing: the ratio of bacterial mortality to growth rate. To test this
hypothesis, we analyzed time-course changes in BCC, protistan grazing rate, and bacterial production from 3 in situ studies conducted in a freshwater reservoir and three laboratory studies. In the field experiments, samples were manipulated
to yield different levels of protistan bacterivory and incubated in dialysis bags. Laboratory investigations were continuous
cultivation studies in which different bacterivorous protists were added to bacterial communities. BCC was assessed using
4–6 different rRNA-targeted oligonucleotide probes for community analysis. Change in BCC (Δ BCC) was estimated as the sum
of changes in the proportions of the two phylogenetic groups that showed the largest shifts. Analysis of a set of 22 estimates
of shifts in the ratio of grazing to production rate over periods of 48–72 h and Δ BCC showed that Δ BCC was positively and
tightly correlated (r
2 = 0.784) with shifts in the ratio of grazing mortality to cell production. While the nature of a shift in BCC is unpredictable,
the magnitude of the change can be related to changes in the balance between bacterial production and protistan grazing.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
100.
Canal construction destroys the barrier between major European invasion lineages of the zebra mussel 总被引:4,自引:0,他引:4
Müller JC Hidde D Seitz A 《Proceedings. Biological sciences / The Royal Society》2002,269(1496):1139-1142
Since the mid-1980s the zebra mussel, Dreissena polymorpha, Pallas 1771, has become the protagonist of a spectacular freshwater invasion in North America due to its large economic and biological impact. Several genetic studies on American populations have failed to detect any large-scale geographical patterns. In western Europe, where D. polymorpha has been a classical invader from the Pontocaspian since the early 19th century, the situation is strikingly different. Here, we show with genetic markers that two major western European invasion lineages with lowered genetic variability within and among populations can be discriminated. These two invasion lineages correspond with two separate navigable waterways to western Europe. We found a rapid and asymmetrical genetic interchange of the two invasion lines after the construction of the Main-Danube canal in 1992, which interconnected the two waterways across the main watershed. 相似文献