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排序方式: 共有206条查询结果,搜索用时 31 毫秒
81.
The relaxosome protein MobC promotes conjugal plasmid mobilization by extending DNA strand separation to the nick site at the origin of transfer 总被引:11,自引:4,他引:7
The frequency of conjugal mobilization of plasmid R1162 is decreased approximately 50-fold if donor cells lack MobC, one of the plasmid-encoded proteins making up the relaxosome at the origin of transfer ( oriT ). The absence of MobC has several different effects on oriT DNA. Site- and strand-specific nicking by MobA protein is severely reduced, accounting for the lower frequency of mobilization. The localized DNA strand separation required for this nicking is less affected, but becomes more sensitive to the level of active DNA gyrase in the cell. In addition, strand separation is not efficiently extended through the region containing the nick site. These effects suggest a model in which MobC acts as a molecular wedge for the relaxosome-induced melting of oriT DNA. The effect of MobC on strand separation may be partially complemented by the helical distortion induced by supercoiling. However, MobC extends the melted region through the nick site, thus providing the single-stranded substrate required for cleavage by MobA. 相似文献
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Shuyu Wu Anders Dalsgaard Anette M Hammerum Lone J Porsbo Lars B Jensen 《Acta veterinaria Scandinavica》2010,52(1):47
Background
Sulfonamide resistance is very common in Escherichia coli. The aim of this study was to characterize plasmids carrying sulfonamide resistance genes (sul1, sul2 and sul3) in E. coli isolated from pigs and humans with a specific objective to assess the genetic diversity of plasmids involved in the mobility of sul genes. 相似文献86.
Shuyu Guan Weiwei Su Ning Wang Peibo Li Yonggang Wang 《Journal of enzyme inhibition and medicinal chemistry》2013,28(2):252-255
Radix Polygoni multiflori is a herb used effectively to prevent graying and treat skin depigmentation diseases in traditional Chinese medicine but its active ingredients have not been discovered yet. In this investigation, we tested six compounds isolated from Radix Polygoni multiflori, to discover the active component on melanogenesis. Three experiments were performed in the present investigation: mushroom tyrosinase activity, melanin content B16 cell proliferation assay. Among all the six components tested, THSG showed the most potent effects on tyrosinase activation and melanogenesis; it was shown to be a potent tyrosinase activator and a melanogenesis stimulator in this study. On the other hand, we found that gallic acid significantly inhibited tyrosinase and, in addition, anthraquinones were cytotoxic to melanoma cells. They were both harmful to melanogenesis. Therefore, we propose that THSG acts as the active ingredient of Radix Polygoni multiflori on melanogenesis. 相似文献
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Zeng G Chen CY Huang D Yao S Wang RC Chen ZW 《Journal of immunology (Baltimore, Md. : 1950)》2011,187(1):190-199
The role of IL-22-producing CD4(+) T cells in intracellular pathogen infections is poorly characterized. IL-22-producing CD4(+) T cells may express some effector molecules on the membrane, and therefore synergize or contribute to antimicrobial effector function. This hypothesis cannot be tested by conventional approaches manipulating a single IL-22 cytokine at genetic and protein levels, and IL-22(+) T cells cannot be purified for evaluation due to secretion nature of cytokines. In this study, we surprisingly found that upon activation, CD4(+) T cells in Mycobacterium tuberculosis-infected macaques or humans could evolve into T effector cells bearing membrane-bound IL-22 after de novo IL-22 production. Membrane-bound IL-22(+) CD4(+) T effector cells appeared to mature in vivo and sustain membrane distribution in highly inflammatory environments during active M. tuberculosis infection. Near-field scanning optical microscopy/quantum dot-based nanoscale molecular imaging revealed that membrane-bound IL-22, like CD3, distributed in membrane and engaged as ~100-200 nm nanoclusters or ~300-600 nm nanodomains for potential interaction with IL-22R. Importantly, purified membrane-bound IL-22(+) CD4(+) T cells inhibited intracellular M. tuberculosis replication in macrophages. Our findings suggest that IL-22-producing T cells can evolve to retain IL-22 on membrane for prolonged IL-22 t(1/2) and to exert efficient cell-cell interaction for anti-M. tuberculosis effector function. 相似文献
89.
Mingxing Yang Xiumin Li Zhibin Li Zhimin Ou Ming Liu Suhuan Liu Xuejun Li Shuyu Yang 《PloS one》2013,8(12)
Motivation
DNA microarray analysis is characterized by obtaining a large number of gene variables from a small number of observations. Cluster analysis is widely used to analyze DNA microarray data to make classification and diagnosis of disease. Because there are so many irrelevant and insignificant genes in a dataset, a feature selection approach must be employed in data analysis. The performance of cluster analysis of this high-throughput data depends on whether the feature selection approach chooses the most relevant genes associated with disease classes.Results
Here we proposed a new method using multiple Orthogonal Partial Least Squares-Discriminant Analysis (mOPLS-DA) models and S-plots to select the most relevant genes to conduct three-class disease classification and prediction. We tested our method using Golub’s leukemia microarray data. For three classes with subtypes, we proposed hierarchical orthogonal partial least squares-discriminant analysis (OPLS-DA) models and S-plots to select features for two main classes and their subtypes. For three classes in parallel, we employed three OPLS-DA models and S-plots to choose marker genes for each class. The power of feature selection to classify and predict three-class disease was evaluated using cluster analysis. Further, the general performance of our method was tested using four public datasets and compared with those of four other feature selection methods. The results revealed that our method effectively selected the most relevant features for disease classification and prediction, and its performance was better than that of the other methods. 相似文献90.