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排序方式: 共有81条查询结果,搜索用时 15 毫秒
1.
Cecilia PC Soh Alastair SR Donald James Feeney Walter TJ Morgan Winifred M Watkins 《Glycoconjugate journal》1989,6(3):319-332
The tetrasaccharides GalNAcß1-4[NeuAc2-3]Galß1-4Glc and GalNAcß1-4[NeuAc2-3]Galß1-4GlcNAc were synthesised by enzymic transfer of GalNAc from UDP-GalNAc to 3-sialyllactose (NeuAc2-3Galß1-4Glc) and 3-sialyl-N-acetyllactosamine (NeuAc2-3Galß1-4GlcNAc). The structures of the products were established by methylation and1H-500 MHz NMR spectroscopy. In Sda serological tests the product formed with 3-sialyl-N-acetyllactosamine was highly active whereas that formed with 3-sialyllactose had only weak activity. 相似文献
2.
Gerald A. Merrill David Miller John Chirgwin Paul M. Horowitz 《Journal of Protein Chemistry》1992,11(2):193-199
Rhodanese has been utilized as a model enzyme for the study of protein structure-function relationships. The enzyme has recently been cloned and the recombinant enzyme is now available for investigation. However, prior to use in structure-function studies, the recombinant enzyme must be shown to have the same structure and activity as the bovine liver enzyme used in the previous studies. An immunological study of the conformations of these enzyme conformers is described. Three antibodies (two monoclonal and one polyclonal, site-directed antibody) were shown to detect distinct and nonoverlapping epitopes. The epitopes of the monoclonal antirhodanese antibodies (R207 and MAB11) were mapped to the same CNBr digest fragment of the amino terminal domain of rhodanese, and the epitope of the site-directed antibody prepared against the interdomain tether sequence of rhodanese (PAT-T1) was mapped to that region of rhodanese (residues 142–156). The rhodanese conformers were studied by monitoring the accessibility of the epitopes recognized by each antibody in each conformer using an indirect ELISA. None of the antibodies could detect its epitope on the purified liver enzyme. Two of the antibodies (R207 and PAT-T1) could also not detect their epitopes on the recombinant enzyme. However, MAB11 did detect a conformational difference between the natural and recombinant rhodanese conformers, indicating the conformational difference is localized in the first 73 amino acids of rhodanese. This difference presumably reflects the difference in the histories of the two enzymes and may be due to differences in enzyme folding, differences in the purification procedures, and differences in storage conditions—all of which could influence the final conformation of the enzyme. 相似文献
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Approaches to breeding for salinity tolerance - a case study on Porteresia coarctata 总被引:2,自引:0,他引:2
R LATHA C SRINIVAS RAO H M SR SUBRAMANIAM P EGANATHAN M S SWAMINATHAN 《The Annals of applied biology》2004,144(2):177-184
Cereals are the world's major source of food for human nutrition. Among these, rice (Oryza sativa) is the most prominent and represents the staple diet for more than two-fifths (2.4 billion) of the world's population, making it the most important food crop of the developing world (Anon., 2000a). Rice production in vast stretches of coastal areas is hampered due to high soil salinity. This is because rice is a glycophyte and it does not grow well under saline conditions. In order to increase rice production in these areas there is a need to develop rice varieties suited to saline environments. Research has shown that Porteresia coarctata, a highly salt tolerant wild relative of rice growing in estuarine soils, is an important material for transferring salt tolerant characteristics to rice. It is quite possible that Porteresia may be used as a parent for evolving better and truly salt resistant varieties. The inadequate results and the difficulties associated with conventional breeding techniques necessitate the use of the tools of crop biotechnology in unravelling some of the characteristics of Porteresia that have been highlighted in this report. In view of the limited resources available for increasing salinity tolerance to the breeders to wild rice germplasm, Porteresia is undoubtedly one of the key source species for elevating salinity tolerance in cultivated rice. 相似文献
5.
Expression of cloned bovine adrenal rhodanese 总被引:2,自引:0,他引:2
D M Miller R Delgado J M Chirgwin S C Hardies P M Horowitz 《The Journal of biological chemistry》1991,266(8):4686-4691
A cDNA for the enzyme rhodanese (thiosulfate:cyanide sulfurtransferase, EC 2.8.1.1) has been cloned from a bovine adrenal library. An initiator methionine codon precedes the amino-terminal amino acid found in the isolated protein. Rhodanese is synthesized in the cytoplasm and transferred to the mitochondrial matrix. Thus, any amino-terminal sequence required for organelle import is retained in the mature protein. Furthermore, the DNA sequence shows that there are three additional amino acids, Gly-Lys-Ala, at the carboxyl terminus that are not found by protein sequencing. Additionally, comparison of the published amino acid sequence with that encoded by the open reading frame revealed three differences in the amino acid sequence. Comparison of the bovine and chicken liver sequences shows an overall level of 70% sequence homology, but there is complete identity of all residues that have been implicated in the function of the enzyme. When two mammalian cells, cos-7 and 293 cells, were transiently transfected with a plasmid containing the rhodanese coding region, rhodanese activity in lysates increased approximately 20-fold. Fluorograms of denaturing polyacrylamide gels detected a large increase in a polypeptide that co-migrated with the native protein and reacted with anti-rhodanese antibodies. Nondenaturing gels showed two active species that co-migrated with the two major electrophoretic forms purified by current procedures. Escherichia coli, transformed with a plasmid containing the rhodanese coding region, showed a 15-fold increase in rhodanese activity over baseline values. When the E. coli recombinant protein was analyzed on a nondenaturing gel, only one species was observed that co-electrophoresed with the more electropositive variant seen in purified bovine liver rhodanese. This single variant could be converted by carboxypeptidase B digestion to a form of the enzyme that co-migrated with the more electronegative species isolated from bovine liver. Thus, two major, enzymatically active electrophoretic variants, commonly observed in mammalian cells, can be accounted for by carboxyl-terminal processing without recourse to other post-translational modifications. 相似文献
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The effect of neurotensin on submaximally-stimulated hepatobiliary and pancreatic secretion was studied in 6 healthy subjects. An intravenous infusion of neurotensin 1.4 ± 0.3 pmol/kg/min, designed to reproduce plasma neurotensin immunoreactivity levels within the physiological range, produced a significant increase in pancreatic bicarbonate output. Plasma concentrations of pancreatic polypeptide rose by 83 ± 16 pmol/l and were associated with a small reduction in trypsin, but no significant change in bilirubin outputs. 相似文献
8.
Ginger R. Zipperer Sridhar Arumugam Sharon R. Chirgwin Sharon U. Coleman Krishna P. Shakya Thomas R. Klei 《Experimental parasitology》2013
Previous studies have shown that intradermally (ID) injected Brugia pahangi L3s migrate through various tissues and into the lymphatics of gerbils in a distinct pattern. Excretory/secretory products (ES) produced at the time of invasion of B. pahangi are likely to be important in this early migration phase of the parasite life cycle in their rodent host. Hence, early L3 ES was collected from 24 h in vitro cultures of B. pahangi L3 larvae and used in immunization experiments to investigate the effect of immunity to early L3 ES on worm migration, survival and development of B. pahangi. Immunization of gerbils with ES in RIBI adjuvant produced antibodies to numerous ES proteins eliciting a strong humoral response to ES and indirect fluorescent antibody (IFA) assay using anti-ES serum recognized the ES proteins on the surface of B. pahangi L3 larvae. Following ES immunization, gerbils were challenged either ID or intraperitoneally (IP) with 100 L3s of B. pahangi and euthanized at 3 or 106 days post inoculation (DPI). Immunization with early ES slowed the migration of ID inoculated L3 at 3 DPI and significantly altered the locations of adult worms at 106 DPI. Immunization did not induce protection in any treatment group. However, immunized animals had significantly fewer microfilariae per female worm suggesting the antigens in ES are important in microfilariae development or survival in the host. The number of lymphatic granulomas was also significantly reduced in ES immunized animals. It is important to note that microfilariae serve as a nidus in these granulomas. Our results shows immunization with early Brugia malayi L3 ES alters the worm migration, affects circulating microfilarial numbers and reduces lymphatic granulomas associated with B. pahangi infection in gerbils. 相似文献
9.
Infection of humans with filarial parasites has long been associated with the maintenance of a dominant Th2-type host immune response. This is reflected by increases in interleukin (IL)-4- and IL-5-producing T cells, elevated immunoglobulin (Ig)E and IgG4 levels, and a pronounced eosinophilia. The Mongolian gerbil (Meriones unguiculatus) is permissive for the filarial nematodes Brugia malayi and B. pahangi. As in humans, persistent microfilaremic infections of gerbils with Brugia spp. results in increases in Th2 cytokines such as IL-4 and IL-5. The association of dominant Th2 cytokine profiles with the maintenance of infection suggests that the introduction of Brugia spp. into a strongly Th1-biased environment may adversely affect parasite establishment. Indeed, studies conducted in mice with B. malayi suggest that depleting Th1 effectors such as interferon (IFN)-gamma and nitric oxide results in increased worm recoveries. In the present studies, the Mongolian gerbil was used as a model to investigate the effect of a dominant Th1 cytokine environment on the establishment of B. pahangi. Intraperitoneal (i.p.) administration of immunostimulatory oligodeoxynucleotide (IS ODN) induced the production of IFN-gamma in the peritoneal exudate cells and spleen of gerbils. The presence of IFN-gamma at the time of B. pahangi infection did result in an altered host immune response to B. pahangi. Gerbils that received IS ODN before i.p. B. pahangi infections showed lower levels of the Th2-type cytokines IL-4 and IL-5, compared with animals that received B. pahangi alone (0 + Bp). This alteration in cytokine profile, however, did not alter the establishment or development of B. pahangi in the peritoneal cavity. Furthermore, there was no difference in the granulomatous response of gerbils to soluble adult B. pahangi antigen bound to beads embolized in their lungs, regardless of treatment group, suggesting that IL-4 and IL-5 are not essential contributors to the systemic host inflammatory response to B. pahangi in this model. 相似文献
10.
Kakonen SM Selander KS Chirgwin JM Yin JJ Burns S Rankin WA Grubbs BG Dallas M Cui Y Guise TA 《The Journal of biological chemistry》2002,277(27):24571-24578
Transforming growth factor (TGF)-beta promotes breast cancer metastasis to bone. To determine whether the osteolytic factor parathyroid hormone-related protein (PTHrP) is the primary mediator of the tumor response to TGF-beta, mice were inoculated with MDA-MB-231 breast cancer cells expressing a constitutively active TGF-beta type I receptor. Treatment of the mice with a PTHrP-neutralizing antibody greatly decreased osteolytic bone metastases. There were fewer osteoclasts and significantly decreased tumor area in the antibody-treated mice. TGF-beta can signal through both Smad and mitogen-activated protein (MAP) kinase pathways. Stable transfection of wild-type Smad2, Smad3, or Smad4 increased TGF-beta-stimulated PTHrP secretion, whereas dominant-negative Smad2, Smad3, or Smad4 only partially reduced TGF-beta-stimulated PTHrP secretion. When the cells were treated with a variety of protein kinases inhibitors, only specific inhibitors of the p38 MAP kinase pathway significantly reduced both basal and TGF-beta-stimulated PTHrP production. The combination of Smad dominant-negative blockade and p38 MAP kinase inhibition resulted in complete inhibition of TGF-beta-stimulated PTHrP production. Furthermore, TGF-beta treatment of MDA-MB-231 cells resulted in a rapid phosphorylation of p38 MAP kinase. Thus, the p38 MAP kinase pathway appears to be a major component of Smad-independent signaling by TGF-beta and may provide a new molecular target for anti-osteolytic therapy. 相似文献