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41.
Zarivach R Ben-Zeev E Wu N Auerbach T Bashan A Jakes K Dickman K Kosmidis A Schluenzen F Yonath A Eisenstein M Shoham M 《Biochimie》2002,84(5-6):447-454
Colicin E3 is a protein that kills Escherichia coli cells by a process that involves binding to a surface receptor, entering the cell and inactivating its protein biosynthetic machinery. Colicin E3 kills cells by a catalytic mechanism of a specific ribonucleolytic cleavage in 16S rRNA at the ribosomal decoding A-site between A1493 and G1494 (E. coli numbering system). The breaking of this single phosphodiester bond results in a complete cessation of protein biosynthesis and cell death. The inactive E517Q mutant of the catalytic domain of colicin E3 binds to 30S ribosomal subunits of Thermus thermophilus, as demonstrated by an immunoblotting assay. A model structure of the complex of the ribosomal subunit 30S and colicin E3, obtained via docking, explains the role of the catalytic residues, suggests a catalytic mechanism and provides insight into the specificity of the reaction. Furthermore, the model structure suggests that the inhibitory action of bound immunity is due to charge repulsion of this acidic protein by the negatively charged rRNA backbone 相似文献
42.
Genes associated with the end of dormancy in grapes 总被引:11,自引:0,他引:11
Pacey-Miller T Scott K Ablett E Tingey S Ching A Henry R 《Functional & integrative genomics》2003,3(4):144-152
A grape bud EST library was constructed and 4,270 ESTs sequenced. The library clones were arrayed for the purpose of investigating the level of gene expression over time, particularly leading up to the buds release from dormancy. The arrays were hybridized with P33-labeled probes produced from samples of buds collected at weekly intervals. These probes covered the time from 9 weeks prior to bud burst until just after the emergence of the shoots. Expression patterns from these genes have been examined. It was found that 74% of the genes in the data set were homologous to known proteins. Genes were then assigned to functional categories according to their primary BLAST match. Of these 13% were involved with photosynthesis, 13% with disease resistance and defense, 5% energy, 12% metabolism, 20% protein production and processing, 25% cell structure and plant growth and the remaining 12% were unclassified The expression pattern of a selection of candidate genes retrieved from literature previously reporting an association with dormancy changes was assessed. On closer examination most of these genes relate to the oxidative processes and stress responses within the cell. The results of this study show that even in the dormant state, gene expression in the buds is high. 相似文献
43.
Ben-Zeev E Zarivach R Shoham M Yonath A Eisenstein M 《Journal of biomolecular structure & dynamics》2003,20(5):669-676
Colicin E3 kills Escherichia coli cells by ribonucleolytic cleavage in the 16S rRNA. The cleavage occurs at the ribosomal decoding A-site between nucleotides A1493 and G1494. The breaking of this single phosphodiester bond results in a complete termination of protein biosynthesis leading to cell death. A model structure of the complex of the ribosomal subunit 30S and colicin E3 was constructed by means of a new weighted-geometric docking algorithm, in which interactions involving specified parts of the molecular surface can be up-weighted, allowing incorporation of experimental data in the docking search. Our model, together with available experimental data, predicts the role of the catalytic residues of colicin E3. In addition, it suggests that bound acidic immunity protein inhibits the enzymatic activity of colicin E3 by electrostatic repulsion of the negatively charged substrate. 相似文献
44.
Ada Ricci Angela Carra Enrico Rolli Cristina Bertoletti Camillo Branca 《Plant Growth Regulation》2003,40(3):207-212
Stem slices cut from micropropagated cuttings of apple rootstock M26 were cultured in the presence of indole-3-butyric acid (IBA) plus N,N-bis-(2,3-methylenedioxyphenyl)urea or N,N-bis-(3,4-methylenedioxyphenyl)urea, to verify if there was an interaction between them in enhancing root formation. The N,N-bis-(methylenedioxyphenyl)ureas were supplemented after, before and in the simultaneous presence of auxin. Our data demonstrate that only the simultaneous presence of auxin and N,N-bis-(methylenedioxyphenyl)ureas in the culture medium enhanced root formation on M26 stem slices. The percentage of rooted slices obtained in the presence of the mixtures was significantly different from that obtained in the presence of low auxin concentration alone (1µM). Moreover both the percentage of rooted slices and the number of roots per slice obtained in these culture conditions was not significantly different to that of the optimal auxinic treatment in which the auxin concentration was threefold higher. 相似文献
45.
Premkumar L Bageshwar UK Gokhman I Zamir A Sussman JL 《Protein expression and purification》2003,28(1):151-157
A 60-kDa, salt-inducible, internally duplicated alpha-type carbonic anhydrase (Dca) is associated with the plasma membrane of the extremely salt-tolerant, unicellular, green alga Dunaliella salina. Unlike other carbonic anhydrases, Dca remains active over a very broad range of salinities (0-4M NaCl), thus representing a novel type of extremely halotolerant enzyme. To elucidate the structural principles of halotolerance, structure-function investigations of Dca have been initiated. Such studies require considerable amounts of the enzyme, and hence, large-scale algal cultivation. Furthermore, the purified enzyme is often contaminated with other, co-purifying algal carbonic anhydrases. Expression in heterologous systems offers a means to produce, and subsequently purify, sufficiently large amounts of Dca required for activity and structural studies. Attempts to over-express Dca in the Escherichia coli BL21(DE3)pLysS strain, after optimizing various expression parameters, produced soluble, but weakly active protein, composed of fully reduced and variably -S-S- cross-linked chains (each of the Dca repeats contains a pair of cysteine residues, presumably forming a disulfide bond). However, when the E. coli Origami B(DE3)pLysS strain was used as a host, a functionally active enzyme with proper disulfide bonds was formed in good yield. Affinity-purified recombinant Dca resembled the native enzyme from D. salina in activity and salt tolerance. Hence, this expression system offers a means of pursuing detailed studies of this extraordinary protein using biochemical, biophysical, and crystallographic approaches. 相似文献
46.
Kolman A 《Alternatives to laboratory animals : ATLA》2003,31(3):241-243
The 20th Annual Workshop on In Vitro Toxicology (Oxford, UK, September 22-24, 2002) was convened as part of a European meeting entitled Human Cell Culture 2002. The meeting was arranged by the Scandinavian Society for Cell Toxicology (SSCT), the European Tissue Culture Society and the British Prostate Group. Two sessions, which are summarised in this report, were devoted to in vitro toxicology: Human Cell Toxicology and The SSCT Free Paper Session. Outstanding experts in the field of toxicology outlined contemporary approaches in toxicity testing in their lectures. Short oral presentations demonstrated a variety of in vitro model systems and methodologies, which can be useful for investigating human toxicity, as well as for studies on mechanisms of toxicity. 相似文献
47.
Like higher plants, unicellular green algae of the genus Dunaliella respond to light stress by enhanced de-epoxidation of violaxanthin and accumulation of Cbr, a protein homologous to early
light-inducible proteins (Elips) in plants. Earlier studies indicated that Cbr was associated with the light-harvesting complex
of photosystem II (LHCII) and suggested it acted as a zeaxanthin-binding protein and fulfilled a photo-protective function
(Levy et al. 1993, J. Biol. Chem. 268: 20892–20896). To characterize the protein-pigment subcomplexes containing Cbr in greater
detail than attained so far, thylakoid membranes from Dunaliella salina grown in high light or normal light were solubilized with dodecyl maltoside and fractionated by isoelectric-focusing. Analysis
of the resolved LHCII subcomplexes indicated preferred associations among the four LHCIIb polypeptides and between them and
Cbr: subcomplexes including Cbr contained one or two of the more acidic of the four LHCIIb polypeptides as well as large amounts
of lutein and zeaxanthin relative to chlorophyll a/b. After sucrose gradient centrifugation, Cbr free of LHCIIb polypeptides
was detected together with released pigments; this Cbr possibly originated in subcomplexes dissociated in the course of the
analysis. These results agree with the conclusion that Cbr is part of the network of LHCIIb protein-pigment complexes and
suggest that the role played by Cbr involves the organization and/or stabilization of assemblies highly enriched in zeaxanthin
and lutein. Such assemblies may function to protect PSII from photodamage due to overexcitation.
Received: 6 August 1999 / Accepted: 23 November 1999 相似文献
48.
Lai Wang Mingjie Yang Ana Arias Lei Song Fuqiang Li Fang Tian Minghui Qin Ada Yukht Ian K. Williamson Prediman K. Shah Behrooz G. Sharifi 《PloS one》2015,10(6)
Extramedullary hematopoiesis has been shown to contribute to the pathogenesis of a variety of diseases including cardiovascular diseases. In this process, the spleen is seeded with mobilized bone marrow cells that augment its hematopoietic ability. It is unclear whether these immigrant cells that are produced/reprogrammed in spleen are similar or different from those found in the bone marrow. To begin to understand this, we investigated the relative potency of adult splenocytes per se to repopulate bone marrow of lethally-irradiated mice and its functional consequences in atherosclerosis. The splenocytes were harvested from GFP donor mice and transplanted into myeloablated wild type recipient mice without the inclusion of any bone marrow helper cells. We found that adult splenocytes repopulated bone marrow of myeloablated mice and the transplanted cells differentiated into a full repertoire of myeloid cell lineages. The level of monocytes/macrophages in the bone marrow of recipient mice was dependent on the cell origin, i.e., the donor splenocytes gave rise to significantly more monocytes/macrophages than the donor bone marrow cells. This occurred despite a significantly lower number of hematopoietic stem cells being present in the donor splenocytes when compared with donor bone marrow cells. Atherosclerosis studies revealed that donor splenocytes displayed a similar level of atherogenic and atheroprotective activities to those of donor bone marrow cells. Cell culture studies showed that the phenotype of macrophages derived from spleen is different from those of bone marrow. Together, these results demonstrate that splenocytes can seed bone marrow of myeloablated mice and modulate atherosclerosis. In addition, our study shows the potential of splenocytes for therapeutic interventions in inflammatory disease. 相似文献
49.
Elisa Rossi Daniela Basso Carlo-Federico Zambon Filippo Navaglia Eliana Greco Michela Pelloso Serena Artuso Andrea Padoan Matilde Pescarin Ada Aita Dania Bozzato Stefania Moz Mara Cananzi Graziella Guariso Mario Plebani 《PloS one》2015,10(4)
Background
TNF-α and IFN-γ play a role in the development of mucosal damage in celiac disease (CD). Polymorphisms of TNFA and IFNG genes, as well as of the TNFRSF1A gene, encoding the TNF-α receptor 1, might underlie different inter-individual disease susceptibility over a common HLA risk background. The aims of this study were to ascertain whether five SNPs in the TNFA promoter (-1031T>C,-857C>T,-376G>A,-308G>A,-238G>A), sequence variants of the TNFRSF1A gene and IFNG +874A>T polymorphism are associated with CD in a HLA independent manner.Methods
511 children (244 CD, 267 controls) were genotyped for HLA, TNFA and INFG (Real Time PCR). TNFRSF1A variants were studied (DHPLC and sequence).Results
Only the rare TNFA-1031C (OR=0.65, 95% CI:0.44-0.95), -857T (OR=0.42, 95% CI:0.27-0.65), -376A (OR=2.25, 95% CI:1.12-4.51) and -308A (OR=4.76, 95% CI:3.12-7.26) alleles were significantly associated with CD. One TNFRSF1A variant was identified (c.625+10A>G, rs1800693), but not associated with CD. The CD-correlated TNFA SNPs resulted in six haplotypes. Two haplotypes were control-associated (CCGG and TTGG) and three were CD-associated (CCAG, TCGA and CCGA). The seventeen inferred haplotype combinations were grouped (A to E) based on their frequencies among CD. Binary logistic regression analysis documented a strong association between CD and HLA (OR for intermediate risk haplotypes=178; 95% CI:24-1317; OR for high risk haplotypes=2752; 95% CI:287-26387), but also an HLA-independent correlation between CD and TNFA haplotype combination groups. The CD risk for patients carrying an intermediate risk HLA haplotype could be sub-stratified by TNFA haplotype combinations.Conclusion
TNFA promoter haplotypes associate with CD independently from HLA. We suggest that their evaluation might enhance the accuracy in estimating the CD genetic risk. 相似文献50.
Steven H. Hendriks Kornelis J. J. van Hateren Klaas H. Groenier Sebastiaan T. Houweling Angela H. E. M. Maas Nanne Kleefstra Henk J. G. Bilo 《PloS one》2015,10(12)