Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The long-term maintenance of human islets in culture has remained a challenge. Despite advancements in culture techniques, human islets proved to have a short life span in vitro. For the first time, we have succeeded in maintaining human islets in a defined culture medium for more than 12 months. Freshly isolated islets from a 38-year-old donor were cultured in M3:5 medium and placed on a rocker for 14 days to remove contaminated exocrine and mesenchymal cells which attached to the bottom. The floating islets were purified by daily hand-picking and transfer into fresh medium. After 14 days, purified islets were allowed to attach to the bottom of the flasks and to expand. At various time points, islets were examined immunohistochemically and electron microscopically, and the secretion of islet hormones and their mRNA were determined by radioimmunoassay and reverse transcriptase polymerase chain reaction, respectively. Within seven days of culture, ductular and acinar cells developed within the initially normal islets. With time, exocrine cell types expanded while the number of the endocrine cells and their secretion decreased. At day 60, only a few endocrine cells were identifiable, whereas most of the cells appeared undifferentiated and expressed cytokeratin 7 and 19, neuron specific enolase, tomato lectin, phaseolus leucoagglutinin, laminin, and vimentin. After 60 days, the culture consisted entirely of undifferentiated cells which could be maintained in culture for 270 days before they became senescent. This is the first report on the long-term maintenance of human islet cells in culture and allows an insight into the complex process of endocrine cell differentiation.
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PMID:Maintenance of human islets in long-term culture. 1126 43

Transcription factors are essential to govern differentiation along the lymphoid lineage from uncommitted hematopoietic stem cells. Although many of these transcription factors have putative roles based on murine knockout experiments, their function in human lymphoid development is less known and was studied further. Transcription factor expression in fresh and cultured adult human bone marrow and umbilical cord blood progenitors was evaluated. We found that fresh CD34(+)Lin(-) cells that are human leukocyte antigen (HLA)-DR(-) or CD38(-) constitutively express GATA-3 but not T-cell factor-1 (TCF-1) or Id-3. Culture with the murine fetal liver cell line AFT024 and defined cytokines was capable of inducing TCF-1 mRNA. However, no T-cell receptor gene rearrangement was identified in cultured progeny. Id-3, a basic helix loop helix factor with dominant negative function for T-cell differentiation transcription factors, also was upregulated and may explain unsuccessful T-cell maturation. To better understand the developmental link between natural killer (NK) cells derived from progenitors, we studied NK cell subsets circulating in blood. CD56(+bright), but not CD56(+dim), NK cells constitutively express TCF-1 by reverse transcriptase polymerase chain reaction and Western blot analysis. The TCF-1 isoform found in CD56(+bright) cells, which express lectin but not immunoglobulin class I recognizing inhibitory receptors, was identical to that induced in NK cell differentiation culture and was distinctly different from isoforms in T cells. These results suggest that TCF-1 does not target human killer immunoglobulin receptor genes, TCF-1 is uniquely expressed in circulating CD56(+bright) NK cells, and specific TCF-1 isoforms may play an important role in regulating NK differentiation from a common NK/T-cell progenitor.
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PMID:T-cell factor-1 expression during human natural killer cell development and in circulating CD56(+) bright natural killer cells. 1130 Nov 90

From the roots of the Chinese medicinal herb Pseudostellaria heterophylla a single-chained lectin with a molecular weight of 36 kDa and high hemagglutinating activity was isolated. The lectin was adsorbed on DEAE-cellulose in 10 mM Tris-HCI buffer (pH 7.4) and was eluted by the same buffer containing 50 mM NaCl. It was adsorbed on SP-Sepharose in 10mM NH4OAc (pH 4.5) and eluted by approximately 0.5 M NaCl in the same buffer. The hemagglutinating activity of the lectin could not be inhibited by a large variety of monosaccharides, but was largely abrogated by exposure to 0.05 M HCl, 0.05M NaOH or 80 degrees C. However, about 50% of the activity remained after exposure to 0.025M NaOH or 40 degrees C. Despite possession of an N-terminal sequence exhibiting some similarity to thaumatin-like proteins with antifungal activity, the lectin was devoid of antifungal activity. The lectin exerted some inhibitory effect on the glycohydrolases alpha-glucosidase, beta-glucosidase and beta-glucuronidase which are involved in HIV infection but had no suppressive action on human immunodeficiency virus-type 1 reverse transcriptase.
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PMID:A novel lectin from Pseudostellaria heterophylla roots with sequence simularity to Kunitz-type soybean trypsin inhibitor. 1144 23

A variety of lectins were tested in vitro for inhibitory action against the activities of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase and the N-glycohydrolases (alpha-glucosidase, beta-glucosidase and beta-glucuronidase). Lectins from Phaseolus vulgaris, Momordica charantia, Ricinus communis and its constituent chains, and Agaricus bisporus were able to inhibit HIV-1 reverse transcriptase. P. vulgaris lectin and A. bisporus lectin were the most potent. The aforementioned lectins had only weak or no inhibitory effects on the glycohydrolases. The inhibitory effect of polysaccharopeptide from the mushroom Coriolus versicolor on HIV-1 reverse transcriptase and alpha-glucosidase was enhanced after chemical modification with chlorosulfonic acid. However, the inhibitory effect of the algal polysaccharide fucoidan on HIV-1 reverse transcriptase and alpha-glucosidase was not augmented by sulfation. Trypsin inhibitors from Phaseolus lunatus and Glycine max, gossypol and alkaloids from Corydalis yanhusuo were able to inhibit HIV-1 reverse transcriptase. Dicoumarol was capable of inhibiting HIV-1 reverse transcriptase, alpha-glucosidase, beta-glucosidase and beta-glucuronidase.
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PMID:Examination of lectins, polysaccharopeptide, polysaccharide, alkaloid, coumarin and trypsin inhibitors for inhibitory activity against human immunodeficiency virus reverse transcriptase and glycohydrolases. 1158 48

We previously isolated a lectin of the Korean mistletoe (Viscum album coloratum). The cDNA clones that encode the A- or the B-chain of the Korean mistletoe lectin were cloned by reverse transcriptase polymerase chain reaction (RT-PCR). The mRNAs that were extracted from the Korean mistletoe were amplified, ligated into the pGEM-T easy vector, and screened with a Korean mistletoe lectin-specific probe. The probe was prepared by PCR amplification of the Korean mistletoe DNA using a primer set designed on the basis of amino acid sequences of the Korean mistletoe lectin that we had purified and reported. Unlike a recent report, which states that the European mistletoe lectin gene has no isoforms, several different clones of the A- and B-chains of the Korean mistletoe lectin were cloned from the same primer set. Three clones of each were selected for sequencing. The sizes of the A-chains were 762, 762, and 768 bp, respectively. The B-chain sizes were 798, 789, and 789 bp, respectively. Each of the clones showed significant variation in the amino acids sequence, including the N-linked glycosylation sites of the lectin. The sequence analysis of each of the Korean lectin clones, in comparison with the European mistletoe lectin and the other type II ribosome binding proteins, is discussed in the text. In addition, Southern blot analysis of the Korean mistletoe genomic DNA, restricted by different enzymes and hybridized with the lectin DNA, showed multi-bands, supporting the existence of multicopy genes or a gene family. These data suggest that heterogeneity of the mistletoe lectin is not only introduced by post-translational modifications, but also by expression of isotypes of the lectin genes.
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PMID:cDNA cloning and sequence analysis of the lectin genes of the Korean mistletoe (Viscum album coloratum). 1171 May 24

A protein designated unguilin was isolated from seeds of the black-eyed pea (Vigna unguiculata). It possesses a molecular weight of 18 kDa and an N-terminal sequence resembling that of cyclophilins and the cyclophilin-like antifungal protein from mung beans, and was adsorbed on Affi-gel blue gel and CM-Sepharose. Unguilin exerted an antifungal effect toward fungi including Coprinus comatus, Mycosphaerella arachidicola, and Botrytis cinerea. In addition, unguilin was capable of inhibiting human immunodeficiency virus-1 reverse transcriptase and the glycohydrolases a- and beta-glucosidases which are involved in HIV infection. Unguilin was devoid of lectin and ribonuclease activities. It inhibited methyl-3H-thymidine uptake by mouse splenocytes and it weakly inhibited translation in a rabbit reticulocyte lysate system. Unguilin resembles mungin in some aspects, but differs from it in others.
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PMID:Isolation of unguilin, a cyclophilin-like protein with anti-mitogenic, antiviral, and antifungal activities, from black-eyed pea. 1173 86

A mannose-binding lectin was isolated from the inner shoots of the chive Allium tuberosum. The procedure involved aqueous extraction, (NH4)2SO4 precipitation, dialysis to remove (NH4)2SO4, affinity chromatography on mannose-agarose, ion exchange chromatography on SP-Sepharose, gel filtration on Superdex 75, and ion exchange chromatography on Mono S. Lectin activity was adsorbed on mannose-agarose, SP-Sepharose, and Mono S. The lectin demonstrated a molecular weight of 13 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration, indicating that it is a single-chain protein. N-terminal sequence analysis revealed its remarkable homology to Allium cepa lectin and similarity to a lesser extent to lectins from members of the Amaryllidaceae, Orchidaceae, and Liliaceae. The lectin manifested mitogenic activity in murine splenocytes and inhibitory activity against human immunodeficiency virus type 1 reverse transcriptase.
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PMID:A monomeric mannose-binding lectin from inner shoots of the edible chive (Allium tuberosum). 1173 87

A homodimeric lectin adsorbed on Affi-gel blue gel and CM-Sepharose and possessing a molecular weight of 67 kDa was isolated from red kidney beans. The hemagglutinating activity of this lectin was inhibited by glycoproteins but not by simple sugars. The lectin manifested inhibitory activity on human immunodeficiency virus-1 reverse transcriptase and alpha-glucosidase. The N-terminal sequence of the lectin exhibited some differences from previously reported lectins from Phaseolus vulgaris but showed some similarity to chitinases. It exerted a suppressive effect on growth of the fungal species Fusarium oxysporum, Coprinus comatus, and Rhizoctonia solani. The lectin had low ribonuclease and negligible translation-inhibitory activities.
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PMID:Isolation of a homodimeric lectin with antifungal and antiviral activities from red kidney bean (Phaseolus vulgaris) seeds. 1173 88

A protein designated chickpea cyclophilin-like antifungal protein (CLAP) was isolated from seeds of the chickpea (Cicer arietinum). Chickpea CLAP was characterized by a molecular weight of 18 kDa and an N-terminal sequence homologous to cyclophilins. The protein was isolated with a procedure involving affinity chromatography on Affi-gel blue gel and ion exchange chromatography on CM-Sepharose. In addition to an inhibitory effect on the growth of fungi including Rhizoctonia solani, Mycosphaerella arachidicola and Botrytis cinerea, the protein was capable of inhibiting human immunodeficiency virus-1 reverse transcriptase. Chickpea CLAP did not possess lectin and ribonuclease activities but it weakly inhibited translation in a rabbit reticulocyte lysate system. The protein stimulated 3H-thymidine incorporation by mouse splenocytes.
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PMID:Isolation of a new cyclophilin-like protein from chickpeas with mitogenic, antifungal and anti-HIV-1 reverse transcriptase activities. 1184 97

A variety of antifungal proteins were isolated from seeds of leguminous plants including French bean, cowpea, field bean, mung bean, peanut and red kidney bean. They were assayed for ability to inhibit human immunodeficiency virus type I (HIV-1) reverse transcriptase, protease and integrase, enzymes essential to the life cycle of HIV-1 . It was found that the cowpea beta-antifungal protein had a high potency in inhibiting HIV-1 protease and HIV-1 integrase. Cowpea alpha-antifungal protein was potent in inhibiting HIV-1 reverse transcriptase and HIV-1 integrase. Peanut antifungal protein was characterized by a high inhibitory activity against HIV-1 integrase and an intermediate potency in inhibiting HIV- I reverse transcriptase and HIV- I protease. French bean thaumatin-like protein expressed low HIV- I protease inhibitory activity and red kidney bean lectin inhibited HIV- I integrase by only a very small extent. Antifungal proteins from the field bean and mung bean had an intermediate potency in inhibitory HIV-1 protease and integrase. However, mung bean antifungal protein was not capable of inhibiting HIV-1 reverse transcriptase. The results indicate that nearly all leguminous antifungal proteins examined were able to inhibit HIV-1 reverse transcriptase, protease and integrase to some extent.
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PMID:Inhibitory effects of antifungal proteins on human immunodeficiency virus type 1 reverse transcriptase, protease and integrase. 1185 77


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