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31.
A second function for pseudouridine synthases: A point mutant of RluD unable to form pseudouridines 1911, 1915, and 1917 in Escherichia coli 23S ribosomal RNA restores normal growth to an RluD-minus strain. 总被引:2,自引:2,他引:0
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This laboratory previously showed that truncation of the gene for RluD, the Escherichia coli pseudouridine synthase responsible for synthesis of 23S rRNA pseudouridines 1911, 1915, and 1917, blocks pseudouridine formation and inhibits growth. We now show that RluD mutants at the essential aspartate 139 allow these two functions of RluD to be separated. In vitro, RluD with aspartate 139 replaced by threonine or asparagine is completely inactive. In vivo, the growth defect could be completely restored by transformation of an RluD-inactive strain with plasmids carrying genes for RluD with aspartate 139 replaced by threonine or asparagine. Pseudouridine sequencing of the 23S rRNA from these transformed strains demonstrated the lack of these pseudouridines. Pseudoreversion, which has previously been shown to restore growth without pseudouridine formation by mutation at a distant position on the chromosome, was not responsible because transformation with empty vector under identical conditions did not alter the growth rate. 相似文献
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Kulshreshtha D. D. Sarbhoy A. K. Raychaudhuri S. P. Khan Abrar M. 《Plant and Soil》1974,41(1):195-197
Plant and Soil - A simple apparatus is described for the collection of root exudates at different intervals without disturbing the root system of the seedling. 相似文献
36.
Extracellular lipase production byRhizopus arrhizus was increased by mutant selection from 130 to 670 μmol FFA per mL per min using UV radiation and aziridine treatment. The
produced lipase was purified 720-fold by ammonium sulfate fractionation and Sephadex G-100 gel filtration. The molar mass
of the produced lipase was determined to be approximately 67 kDa which comigrated with bovine serum albumin in both a Sephadex
G-100 column and SDS-PAGE. 相似文献
37.
Plantago ovata Forsk is an annual herb with immense medicinal importance, the seed and husk of which is used in the treatment of chronic constipation, irritable bowel syndrome, diarrhea since ancient times. Zinc, an essential metal, is required by plants as they form important components of zinc finger proteins and also aid in synthesis of photosynthetic pigments such as chlorophyll. However, in excess amount Zn causes chlorosis of leaf and shoot tissues and generate reactive oxygen species. The present study is aimed at investigating the changes in expression levels of MT2 gene in Plantago ovata under zinc stress. Data show up to 1.66 fold increase in expression of PoMT2 in 1000 µM ZnSO4·7H2O treated sample. Our study also describes alteration of MT2 gene expressions in Plantago ovata as observed through Real time PCR (qPCR) done by \(2^{{ - \Delta \Delta}} C_T\) method. In this study we have observed an upregulation (or induction) in the PoMT2 gene expression level in 500 and 800 µM ZnSO4·7H2O treated samples but found saturation on further increasing the dose to 1000 µM of ZnSO4·7H2O. Determination of the phenotypic and biochemical changes in Plantago ovata due to exposure to zinc stress of concentrations 500, 800 and 1000 µM revealed oxidative stress. The enhanced expression of MT2 gene in Plantago ovata has a correlation with the increased total antioxidant activity and increased DPPH radical scavenging activity. 相似文献
38.
Raychaudhuri S Majumder P Sarkar S Giri K Mukhopadhyay D Bhattacharyya NP 《Proteins》2008,71(4):1686-1698
To characterize HYPK, originally identified as a novel huntingtin (Htt) interacting partner by yeast two hybrid assay, we used various biophysical and biochemical techniques. The molecular weight of the protein, determined by gel electrophoresis, was found to be about 1.3-folds ( approximately 22 kDa) higher than that obtained from mass spectrometric analysis (16.9 kDa). In size exclusion chromatography experiment, HYPK was eluted in three fractions, the hydrodynamic radii for which were calculated to be approximately 1.5-folds (23.06 A) higher than that expected for globular proteins of equivalent mass (17.3 A). The protein exhibited predominantly (63%) random coil characteristics in circular dichroism spectroscopy and was highly sensitive to limited proteolysis by trypsin and papain, indicating absence of any specific domain. Experimental evidences with theoretical analyses of amino acids composition of HYPK and comparison with available published data predicts that HYPK is an intrinsically unstructured protein (IUP) with premolten globule like conformation. In presence of increasing concentration of Ca(2+), HYPK showed conformational alterations as well as concomitant reduction of hydrodynamic radius. Even though any link between the natively unfolded nature of HYPK, its conformational sensitivity towards Ca(2+) and interaction with Htt is yet to be established, its possible involvement in Huntington's disease pathogenesis is discussed. 相似文献
39.
Joanna Skommer Tom Brittain Subhadip Raychaudhuri 《Apoptosis : an international journal on programmed cell death》2010,15(10):1223-1233
BH3 mimetics have been proposed as new anticancer therapeutics. They target anti-apoptotic Bcl-2 proteins, up-regulation of
which has been implicated in the resistance of many cancer cells, particularly leukemia and lymphoma cells, to apoptosis.
Using probabilistic computational modeling of the mitochondrial pathway of apoptosis, verified by single-cell experimental
observations, we develop a model of Bcl-2 inhibition of apoptosis. Our results clarify how Bcl-2 imparts its anti-apoptotic
role by increasing the time-to-death and cell-to-cell variability. We also show that although the commitment to death is highly
impacted by differences in protein levels at the time of stimulation, inherent stochastic fluctuations in apoptotic signaling
are sufficient to induce cell-to-cell variability and to allow single cells to escape death. This study suggests that intrinsic
cell-to-cell stochastic variability in apoptotic signaling is sufficient to cause fractional killing of cancer cells after
exposure to BH3 mimetics. This is an unanticipated facet of cancer chemoresistance. 相似文献
40.
Tumor-specific idiotype vaccines. III. Induction of T helper cells by anti-idiotype and tumor cells 总被引:1,自引:0,他引:1
S Raychaudhuri Y Saeki J J Chen H Kohler 《Journal of immunology (Baltimore, Md. : 1950)》1987,139(6):2096-2102
In a previous report, we have demonstrated the induction of tumor-specific immunity by monoclonal anti-idiotype antibodies generated against a monoclonal anti-tumor antibody, 11C1, that also cross-reacts with mouse mammary tumor virus envelope glycoprotein gp52. Also, we showed that whereas one anti-idiotype antibody, 2F10, could induce protective immunity, another anti-idiotype antibody, 3A4, induced nonprotective immunity. Here we demonstrated the existence of T helper cells which recognize anti-idiotypes that exert differential controls on tumor growth. The qualitative nature of idiotype recognizing T cells generated in response to 2F10, 3A4, irradiated tumor, and progressively growing tumor was compared. The reactivity pattern of idiotype recognizing T cells obtained from 2F10 and irradiated tumor immunized mice were similar in nature in the sense that Lyt-2- T cells obtained from these immunized mice responded to both 2F10 and 3A4 as antigen, although T cells from tumor immunized mice responded better to 3A4 antigen. On the other hand, the idiotype-recognizing T cells obtained from 3A4-immunized mice showed a similar reactivity pattern to T cells isolated from mice during the early phase of tumor growth (within day 4 to 5 after the inoculation of 10(4) live tumor cells). Lyt-2- T cells isolated from mice immunized with 3A4 or during the early phase of tumor growth responded only to 3A4 antigen. The inability of Lyt-2- T cells, isolated from 4- to 5-day-old tumor in mice, to cooperate with 2F10-TNP is not due to the absence of 2F10 idiotype recognizing T cells as 2F10 id recognizing T cells are present when examined at the precursor level. These data on the idiotype specificity of T helper cells show a correlation with the presence of anti-tumor immunity. This information will help in the design and application of idiotype vaccine in tumor immunotherapy. 相似文献