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991.
《Molecular & general genetics : MGG》1997,256(2):195-202
A transposable element has been isolated from the entomopathogenic fungus Beauveria bassiana by trapping it in the nitrate reductase structural gene, which has been cloned from this species. The element had inserted
in the first exon of the nia gene and appeared to have duplicated the sequence TA at the site of insertion. It was 3336 bp long with 30-bp imperfect, inverted,
terminal repeats. The element, called hupfer, contained an open reading frame encoding a 321-amino acid protein similar to the IS630- or mariner-Tc1-like transposases, and a residual sequence of about 2 kb which was not significantly similar to any published sequence. There
are fewer than five copies of this transposable element present per genome in the fungus.
Received: 12 February 1997 / Accepted: 2 May 1997 相似文献
992.
993.
Xiaoliang Liu Akemi Ota Michiko Watanabe Shigeharu Ueda Atsushi Saitoh Hideo Shinagawa Atsuo Nakata Takashi Kurimura Xiaoui Wang Yu Zhao Kiyoshi Kondo Jiro Seki Shinichi Miyake Nobuo Sakato Hajime Fujio 《Microbiology and immunology》1995,39(10):775-785
We investigated the murine antibody response to recombinant p17 (rp17) of human immunodeficiency virus type 1 (HIV-1) and the human antibody response directed to p17 in HIV-1 infection. Three large peptides covering residues 12-29, 53-87 and 87-115 of p17 were synthesized. The cysteine residues 57 and 87 of peptide 53-87 were reoxidized to form a disulfide bridge. Eighteen out of 19 murine monoclonal anti-rp17 antibodies had relatively high affinities (KA = 1.9 × 105?1.4 × 108 M?1) with one of the 3 p17 peptides in the liquid phase. Each monoclonal antibody reacted only with one particular peptide and had no reactivity with the other 2 p17 peptides. All the monoclonal antibodies reacted with rp17 in the liquid phase with a reasonable degree of affinity (KA = 2.0 × 105?1.8 × 107 M?1). Four HIV-1 carrier sera, which were positive in ELISA using rp17 as the antigen, reacted positively in an ELISA using 3 p17 peptides which were used to titrate murine monoclonal antibodies. Murine monoclonal antibodies having specificity for the 3 p17 peptides stained live HIV-1-infected cells by means of indirect membrane immunofluorescence, irrespective of their specificity. This suggests that the various portions of p17 (at least 3 regions of p17) were exposed on the surface of live infected cells, probably as short polypeptide chains. 相似文献
994.
高必需氨基酸转基因马铃薯的研究 总被引:8,自引:0,他引:8
80年代以来,马铃薯遗传转化系统日趋成熟,转基因工程植株已被广泛应用于基础科学研究[1]。作为食物蛋白和能量主要来源的马铃薯,提高其蛋白质含量及质量的遗传工程研究正受到人们的普遍关注[2]。Yang等[2]将旨在改善氨基酸平衡的CAT-HEAAE(氯酶素乙酰转移酶-高含量人体必需氨基酸)融合基因导入马铃薯,获得了Southernblot、Northernblot、Westernblot的证据,但尚缺少氨基酸分析的资料。玉米醇溶蛋白(zein)[3]是一个富含甲硫氨酸的贮存蛋白,它和人工合成的HE… 相似文献
995.
996.
Zbigniew Darzynkiewicz 《Journal of cellular biochemistry》1995,58(2):151-159
There is a strong evidence that administration of antitumor drugs triggers apoptotic death of target cells. A characteristic feature of appotosis is active participation of the affected cell in its demise. Attempts have been made, therefore, to potentiate the cytotoxicity of a variety of agents by modulating the propensity of cells to respond by apoptosis. Several strategies to enhance apoptosis that involve modulation of the cell cycle or differentiation are discussed. Loss of control of the G1 checkpoint in tumor cells allows one to design treatments that arrest normal cells at the checkpoint and attempt to selectively kill tumor cells with S phase specific drugs. The possibility of a restoration of the apoptosis triggering function of the tumor suppressor gene p53 when the G1 checkpoint function is abolished is expected to increase tumor cells' sensitivity to S phase poisons. Because induction of apoptosis by many antitumor drugs is cell cycle phase specific, drug combinations that preferentially trigger apoptosis at different phases of the cycle, or recruitment of cells to the sensitive phase, offer another antitumor strategy. There is also evidence that apoptosis is potentiated when cell differentiation is triggered follwing DNA damage. This observation suggests that strategies which combine DNA damaging and differentiating drugs, under conditions where the latter are administered following DNA damage caused by the former, may be successful. 相似文献
997.
Rajiv Kumar 《Journal of cellular biochemistry》1995,57(3):392-398
The central role of 1α,25-dihydroxyvitamin D3 in the regulation of calcium balance is well established. By increasing the absorption of calcium in the intestine and the reabsorption of filtered calcium in the kidney tubule, the hormone maintains an appropriate calcium balance. The cellular mechanisms that underlie the increase in calcium transport in epithelial cells in response to 1α,25-dihydroxyvitamin D3 are beginning to be defined. These events include an increase in the movement of calcium across the apical membrane of the cell, an increase in the movement of calcium across the cell, and an increase in the extrusion of calcium at the basolateral portion of the cell. In this Prospects article, I will discuss the nature of the various processes and proteins involved in transcellular calcium movement, and I will attempt to highlight various future areas of research. 相似文献
998.
In the present investigation we studied the metabolism of 1α,25-dihydroxy-[1β-3H] vitamin D3 (3H-1,25(OH)2D3) in culture-grown human keratinocytes (CHK). Our results showed that the cellular uptake of 3H-1,25(OH)2D3, upon incubation with CHK, occurred very rapidly; and it paralleled a decrease in the concentration of 3H-1,25(OH)2D3 in the medium. The amount of 3H-calcitroic acid, on the other hand, increased slowly in the medium, while the concentration of 3H-calcitroic acid in the cell remained undetectable during the whole period of incubation. When the cells were preincubated with 1,25(OH)2D3 (10?8M), conversion of 3H-1,25(OH)2D3 to 3H-calcitroic acid increased almost twofold, indicating that 1,25(OH)2D3 catalyzed its own catabolism. © 1995 Wiley-Liss, Inc. 相似文献
999.
Omar Benzakour Chryso Kanthou Florea Lupu Ulla Dennehy Chris Goodwin Michael F. Scully Vijay V. Kakkar David N. Cooper 《Journal of cellular biochemistry》1995,59(4):514-528
Thrombin is a potent mitogen for human vascular smooth muscle cells (HVSMC) and its enzymatic activity is required for this function. The present study demonstrates that prothrombin is also mitogenic for HVSMC due to the generation of enzymatically active thrombin which occurs upon incubation of prothrombin with the cells. Analysis by SDS-PAGE, immunoblotting, and amino acid sequencing revealed that prothrombin incubated with HVSMC undergoes limited proteolysis. Prethrombin 1 was formed through cleavage at R155-S156. Cleavage at R271-T272 generated fragment 1.2 and prethrombin 2 whilst cleavage at R284-T285 yielded truncated prothrombin 2 (prethrombin 2′). However, cleavage at R320-I321 which, during prothrombin activation produces two-chain α-thrombin, was not detectable. Studies on HVSMC-conditioned medium revealed that a similar pattern of prothrombin cleavage occurred by a cell-secreted factor(s). Amidolytic activity analysis indicated that 1–3% catalytically active thrombin-like activity was generated upon incubation of prothrombin with HVSMC-conditioned medium. By treating conditioned medium with various classes of proteinase inhibitors or hirudin, it was determined that prothrombin is cleaved by a cell-derived serine proteinase-like factor(s) at R271-S272 and by α-thrombin at R155-S156 and R284-T285. Antibodies neutralising the activity of either urokinase, tissue plasminogen activator, or factor Xa failed to alter the prothrombin cleaving activity of conditioned medium. This activity which may catalyse an alternative pathway for the generation of thrombin, was eluted from a gel filtration column as a single peak with apparent molecular mass of 30–40 kDa. © 1995 Wiley-Liss, Inc. 相似文献
1000.
John P. Williams Hanjoong Jo Ruthann E. Hunnicutt David L. Brautigan Jay M. McDonald Dr. 《Journal of cellular biochemistry》1995,57(3):415-422
Inhibitor 2 is a heat-stable protein that complexes with the catalytic subunit of type-1 protein phosphatase. The reversible phosphorylation of Thr 72 of the inhibitor in this complex has been shown to regulate phosphatase activity. Here we show that inhibitor 2 can also be phosphorylated on tyrosine residues. Inhibitor 2 was 32P-labeled by the insulin receptor kinase in vitro, in the presence of polylysine. Phosphorylation of inhibitor 2 was accompanied by decreased electrophoretic mobility. Dephosphorylation of inhibitor 2 by tyrosine phosphatase 1B, restored normal electrophoretic mobility. Phosphotyrosine in inhibitor 2 was detected by immunoblotting with antiphosphotyrosine antibodies and phosphoamino acid analysis. In addition, following tryptic digestion, one predominant phosphopeptide was recovered at the anode. The ability of inhibitor 2 to inhibit type-1 phosphatase activity was diminished with increasing phosphorylation up to a stoichiometry of 1 mole phosphate incorporated/mole of inhibitor 2, where inhibitory activity was completely lost. These data demonstrate that inhibitor 2 can be phosphorylated on tyrosine residues by the insulin receptor kinase, resulting in a molecule with decreased ability to inhibit type-1 phosphatase activity. 相似文献