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951.
An efficient screening method following UV mutagenesis yielded a high frequency of improved mutants of Trichosporon brassicae CGMCC 0574, a wild-type esterase-producer capable of enantioselectively hydrolyzing the ethyl ester of ketoprofen [2-(3-benzoylphenyl)
propionic acid]. The mutant had an activity 1.8-fold higher than the wild type and was stable in its enzyme production for
ten serial transfers. As the best single carbon source, isopropanol improved the specific activity of the enzyme 5-fold; and
this did not result from the effect of cell permeabilization. An 18-h culture grown on a medium containing 0.5% glucose plus
0.5% isopropanol produced 3-fold as much esterase as a culture grown on 1% glucose. 相似文献
952.
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955.
Dhanvantari S Shen FS Adams T Snell CR Zhang C Mackin RB Morris SJ Loh YP 《Molecular endocrinology (Baltimore, Md.)》2003,17(9):1856-1867
In familial hyperproinsulinemia, specific mutations in the proinsulin gene are linked with a profound increase in circulating plasma proinsulin levels. However, the molecular and cellular basis for this disease remains uncharacterized. Here we investigated how these mutations may disrupt the sorting signal required to target proinsulin to the secretory granules of the regulated secretory pathway, resulting in the unregulated release of proinsulin. Using a combination of molecular modeling and site-directed mutagenesis, we have identified structural molecular motifs in proinsulin that are necessary for correct sorting into secretory granules of endocrine cells. We show that membrane carboxypeptidase E (CPE), previously identified as a prohormone-sorting receptor, is essential for proinsulin sorting. This was demonstrated through short interfering RNA-mediated depletion of CPE and transfection with a dominant negative mutant of CPE in a beta-cell line. Mutant proinsulins found in familial hyperproinsulinemia failed to bind to CPE and were not sorted efficiently. These findings provide evidence that the elevation of plasma proinsulin levels found in patients with familial hyperproinsulinemia is caused by the disruption of CPE-mediated sorting of mutant proinsulins to the regulated secretory pathway. 相似文献
956.
957.
Foot-and-mouth disease virus VP1 protein fused with cholera toxin B subunit expressed in Chlamydomonas reinhardtii chloroplast 总被引:14,自引:0,他引:14
A Chlamydomonas reinhardtii chloroplast expression vector, pACTBVP1, containing the fusion of the foot and mouth disease virus (FMDV) VP1 gene and the cholera toxin B subunit (CTB) gene was constructed and transfered to the chloroplast genome of C. reinhardtii by the biolistic method. The transformants were identified by PCR, Southern blot, Western blot and ELISA assays after selection on resistant medium and incubation in the dark. The CTBVP1 fusion protein was expressed in C. reinhardtii chloroplast and accounted for up to 3% of the total soluble protein. The fusion protein also retained both GM1-ganglioside binding affinity and antigenicity of the FMDV VP1 and CTB proteins. These experimental results support the possibility of using transgenic chloroplasts of green alga as a mucosal vaccine source. 相似文献
958.
Elevated erbB2 expression is detected in many in situ and invasive human ductal carcinomas. Anti-erbB2 antibody directed at the extracellular domain of erbB2 can result in an antitumor response in some patients with tumors overexpressing erbB2 oncoprotein. By combining interleukin 2 (IL-2) activities with a tumor specific antibody, immunotherapy of tumors might be more effective in the future. In this study, a fusion protein consisting of erbB2 single chain antibody (scFv), Fc fragment of human IgG1 and IL-2 was constructed. The molecular weight of fusion proteins is 66 kDa, only one third of whole antibody-IL-2 fusion protein or 44% whole Ig molecule. The fusion proteins retained the activities of both antigen binding and IL-2. The scFv-Fc-IL-2 fusion protein may have advantages over whole antibody-IL-2 fusion proteins, such as smaller molecule, better activity of penetration, more favorable pharmacokinetic properties. 相似文献
959.
Wenhua L Ruming Z Zhixiong X Xiangdong C Ping S 《Biological trace element research》2003,94(2):167-177
Rare earth elements have been emitted into the environment largely as fertilizer components. This has caused much fear about
whether they would influence our environment, especially on the metabolism and genetics of microorganisms. In this article,
the trivalent ion of a rare earth element, lanthanum, was studied for the effects on growth, transformation, and gene expression
of Escherichia coli. The results showed that La3+ at concentrations from 50 to 150 μg/mL stimulated the endogenic metabolism and ectogenic metabolism, but had few effects
on gene expression. La3+ at lower concentrations from 0.5 to 30 μg/mL inhibit intensively E. coli-absorbing external DNA, decreasing the transformation efficiency. It is also supported by observations using transmission
electron microscopy. Our results are significant in understanding the function of rare earth elements to microorganisms and
assessing the risk of application of rare earth compounds. 相似文献
960.
In preparing intracellular microbial samples for one- or two-dimensional electrophoresis, trichloroacetic acid (TCA) precipitation is frequently used to remove interfering compounds. Solubilization of TCA precipitate typically requires the addition of a number of chaotropes or detergents, in a multistep process, that requires hours to carry out. In this study, a simple, rapid, one-step method to solubilize TCA precipitated proteins is presented. Precipitated proteins are pretreated with 0.2 M NaOH for less than 5 min, followed by addition of standard sample solubilization buffer (SSSB). When compared to solubilization with SSSB alone, NaOH pretreatment of TCA-precipitated intracellular protein from Aspergillus oryzae and Escherichia coli shows an approximate 5-fold increase in soluble protein. In addition, two-dimensional gel electrophoresis on resolubilized proteins shows an equivalent number of proteins in samples with and without NaOH pretreatment. 相似文献