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)

Ticks have an efficient defense system for preventing microbial infection. The antimicrobial peptide defensin is one effective molecule in this system. Here we investigated immune competence and the involvement of defensin in the humoral defense of the soft tick, Ornithodoros moubata. Semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) revealed that gene expression of all four defensin isoforms was up-regulated by bacteria or bacterial components. Defensin gene up-regulation by hemocoelic inoculation of bacteria involves the midgut and granulocytes. In immunodetection analysis, immunization by bacterial injection increases the relative concentration of defensin-like material in the hemolymph plasma. Furthermore, elevated antibacterial activity against Gram-positive bacteria but not against Gram-negative bacteria was observed after immunization by a liquid growth inhibition assay. Therefore, enhanced anti-Gram-positive bacterial activity appears to be partially dependent on the release of defensin into the hemolymph. These findings demonstrate that defensin plays an important role in the up-regulated humoral response of O. moubata.
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PMID:Up-regulated humoral immune response in the soft tick, Ornithodoros moubata (Acari: Argasidae). 1455 75

Defensins are thought to play a major role in the defence of small intestinal crypts against colonisation by potential pathogens. In humans two alpha-defensins, HD5 and HD6 and two beta-defensins, hBD1 and hBD2, probably contribute to the antimicrobial barrier, but there are no data to indicate how the expression of these defensin genes might vary in individuals and in populations. To begin to address this question we developed a competitive reverse transcriptase polymerase chain reaction (RT-PCR) assay to quantify HD5 and HD6 mRNA and used it to measure transcripts in small intestinal biopsy tissue from adults living in London, UK, or in Lusaka, Zambia. We also measured alpha- and beta-defensin mRNA in biopsies collected in London from different regions of the small intestine. Jejunal biopsies (n=169) from 83 adults in Lusaka contained approximately one order of magnitude less HD5 and HD6 mRNA than biopsies (n=33) obtained from 27 adults in London. HD5 and HD6 transcript levels were high throughout duodenum, jejunum and ileum. hBD1 and hBD2 mRNA were detected in some, but not all, biopsies from normal small intestine. These data suggest that alpha-defensin expression is down-regulated in tropical populations, and that there are distinct pathways regulating transcription of alpha- and beta-defensins.
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PMID:Intestinal defensin gene expression in human populations. 1456 94

We have identified and analyzed the mRNA sequence of 20 new defensin-like peptides from 11 Australian termite species of Nasutitermes and from an outgroup, Drepanotermes rubriceps. The sequence was amplified by reverse transcriptase PCR with a degenerate primer designed from termicin, an antifungal peptide previously characterized from the termite Pseudocanthotermes spiniger. All 20 genes show high sequence identity with P. spiniger termicin and have duplicated repeatedly during the radiation of Nasutitermes. Comparison of the relative fixation rates of synonymous (silent) and nonsynonymous (amino acid altering) mutations indicates that the Nasutitermes termicins are positively selected. This positive selection appears to drive a decrease in termicin charge. In termites with two genes, the decrease in charge is predominantly restricted to one termicin. Furthermore, the spread of charge is significantly greater within species than across species among amino acid sites that appear to be under strong positive selection and this spread is attributable to only three sites. Our results suggest that after termicin duplication, certain critical sites have maintained a positive charge in one duplicate and evolved towards neutrality in the other and that positive selection has directed these changes repeatedly and independently. This diversification among duplicated genes may be a counter-response to the evolution of fungal resistance in social insects that are particularly vulnerable to fungal epidemics.
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PMID:Duplication and diversifying selection among termite antifungal peptides. 1531 79

An antifungal peptide with a molecular mass around 7 kDa and an N-terminal sequence highly homologous to defensin was isolated from ground beans (Vigna sesquipedalis cv. 'Ground Bean'). The peptide was adsorbed on Affi-gel blue gel and on Mono S. It exerted an antifungal action on Botrytis cinerea, Fusarium oxysporum and Mycosphaerella arachidicola; and an antibacterial action on Escherichia coli B, Proteus vulgaris, Mycobacterium phlei and Bacillus megaterium. The antimicrobial activity was inhibited in presence of the 5 mM CaCl2 and MgCl2, but no inhibition was observed in 5 mM NaCl. The peptide exerted antiproliferative activity toward breast cancer (MCF-7) cells and leukemia M1 cells, this activity could not be inhibited by the ions mentioned above. It also exhibited some inhibitory activity toward human immunodeficiency virus-type 1 reverse transcriptase.
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PMID:Sesquin, a potent defensin-like antimicrobial peptide from ground beans with inhibitory activities toward tumor cells and HIV-1 reverse transcriptase. 1594 29

The gene encoding Trichosanthes kirilowii defensin (TDEF1) was cloned by reverse transcriptase-polymerase chain reaction (RT-PCR). The newly discovered TDEF1 cDNA contains 231 bp (Genbank accession number DQ526373) and encodes a 76-amino acid protein, which consists of a 29-amino acid signal peptide and a 47-amino acid mature peptide. The partial cDNA, corresponding to the mature peptide coding region of TDEF1, was inserted into bacterial expression vector pET32a(+). Subsequent expression showed that TDEF1 was produced as a 26-kDa fusion protein in the form of inclusion body in Escherichia coli BL21 (DE3). After protein refolding and purification, the fusion TDEF1 displayed an inhibitive activity against the fungal pathogen, Fusarium oxysporum, with EC(50) of 247 microg/ml by means of fungal growth inhibition method.
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PMID:Bacterial expression of a Trichosanthes kirilowii defensin (TDEF1) and its antifungal activity on Fusarium oxysporum. 1702 71

A purification protocol is described herein for concurrent isolation of two defense proteins including a 6-kDa defensin-like antifungal peptide and a 60-kDa dimeric hemagglutinin from seeds of the French bean (Phaseolus vulgaris). It involved ion-exchange chromatography on SP-Sepharose, affinity chromatography on Affi-gel blue gel, ion-exchange chromatography on Q-Sepharose, and gel filtration on Superdex Peptide (for defensin-like antifungal peptide) or Superdex 200 (for hemagglutinin). Both antifungal and hemagglutinating activities were adsorbed on SP-Sepharose and then on Affi-gel blue gel. Hemagglutinin was subsequently unadsorbed and defensin-like antifungal peptide adsorbed on Q-Sepharose. The antifungal activity of the antifungal peptide was stable in the temperature range of 0-90 degrees C for 20 min, in the pH range of 4-10, and after exposure to trypsin (1 mg/ml) at 37 degrees C for 1 h. The hemagglutinin was stable from 10 to 80 degrees C, from pH 1 to 12, and after treatment with trypsin at 37 degrees C for 2 h. It inhibited [methyl-(3)H]thymidine incorporation into breast cancer (MCF-7), leukemia (L1210), hepatoma (HepG2) and human embryonic liver (WRL68) cells with an IC50 of 6.6, 7, 13 and 15 microM, respectively, and elicited maximal mitogenic response from mouse splenocytes at 1 microM concentration. It curtailed HIV-1 reverse transcriptase activity with an IC50 of 1.9 microM, but was devoid of antifungal activity.
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PMID:Concurrent purification of two defense proteins from French bean seeds: a defensin-like antifungal peptide and a hemagglutinin. 1799 41

The oral cavity is an environment challenged by a large variety of pathogens. Consequently, the antimicrobial peptides expressed in that environment are interesting as they evolved to defend against a broad spectrum of bacteria and fungi. Here we report the discovery of new alpha-defensins from rhesus macaque oral mucosa and determine the first alpha-defensin structure from that species. The new peptides were identified by sequencing of reverse transcriptase-PCR products obtained from oral mucosal tissues, disclosing three mucosal alpha-defensins, termed rhesus macaque oral alpha-defensins (ROADs). The peptide corresponding to fully processed ROAD-1 was synthesized, subjected to folding/oxidation conditions, and purified. ROAD-1 was active against Staphylococcus aureus, Escherichia coli, and Candida albicans in a concentration-dependent manner. We determined the structure of ROAD-1 using NMR spectroscopy and find that the synthetic peptide adopts the canonical disulfide pairing and alpha-defensin fold. The antimicrobial mechanism of defensins has been correlated with their ability to disrupt and permeabilize the cell envelope, activities that depend on the surface features of the folded peptide. Although ROAD-1 maintains the defensin fold, the oral defensin displays distinct surface features when compared with other alpha-defensin structures.
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PMID:Synthesis, structure, and activities of an oral mucosal alpha-defensin from rhesus macaque. 1893 Sep 22

Several antimicrobial/parasitic peptides are known to be upregulated in mosquitoes upon infection with parasites. The aim of this study was to identify immune-responsive genes in the vector mosquito, Culex quinquefasciatus Say (Diptera: Culicidae) against the human lymphatic filarial parasite, Wuchereria bancrofti (Cobbold) (Spirurida: Onchocercidae). Suppression subtractive hybridization was performed using RNA from filarial infected and non-infected mosquitoes to obtain differentially expressed transcripts, and their identities were confirmed through reverse transcriptase polymerase chain reaction (RT-PCR). Out of 23 clones selected from the suppression subtractive library, three corresponded to antimicrobial peptide genes, defensins, and four corresponded to regulatory serpin peptide genes. RT-PCR using defensin-specific primers and sequencing of the product showed a 284-bp defensin cDNA. Sequence alignment with defensins of the mosquitoes Anopheles gambiae s.s. Giles and Aedes aegypti (L.) showed maximum homology with the former. Similarly, that of serpin-specific primers showed a 406-bp cDNA encoding serpins. Sequence alignment showed maximum homology with that of An. gambiae, as in the case of defensins. Hence, this investigation revealed upregulation of defensins and serpins in Cx quinquefasciatus infected with W. bancrofti. Antimicrobial peptide genes such as defensins may have limited or no specific role in regulating parasite development. Serpins may prove to be facilitating molecules, by regulating melanization of the parasite. However, the exact functions of these molecules in the immune system of the vector mosquito are yet to be investigated.
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PMID:Identification of immune-responsive genes in the mosquito Culex quinquefasciatus infected with the filarial parasite Wuchereria bancrofti. 1912 Sep 67

The Asiatic honeybee, Apis cerana Fabricius, is an important honeybee species in Asian countries. It is still found in the wild, but is also one of the few bee species that can be domesticated. It has acquired some genetic advantages and significantly different biological characteristics compared with other Apis species. However, it has been less studied, and over the past two decades, has become a threatened species in China. We designed primers for the sequences of the four antimicrobial peptide cDNA gene families (abaecin, defensin, apidaecin, and hymenoptaecin) of the Western honeybee, Apis mellifera L. and identified all the antimicrobial peptide cDNA genes in the Asiatic honeybee for the first time. All the sequences were amplified by reverse transcriptase-polymerase chain reaction (RT-PCR). In all, 29 different defensin cDNA genes coding 7 different defensin peptides, 11 different abaecin cDNA genes coding 2 different abaecin peptides, 13 different apidaecin cDNA genes coding 4 apidaecin peptides and 34 different hymenoptaecin cDNA genes coding 13 different hymenoptaecin peptides were cloned and identified from the Asiatic honeybee adult workers. Detailed comparison of these four antimicrobial peptide gene families with those of the Western honeybee revealed that there are many similarities in the quantity and amino acid components of peptides in the abaecin, defensin and apidaecin families, while many more hymenoptaecin peptides are found in the Asiatic honeybee than those in the Western honeybee (13 versus 1). The results indicated that the Asiatic honeybee adult generated more variable antimicrobial peptides, especially hymenoptaecin peptides than the Western honeybee when stimulated by pathogens or injury. This suggests that, compared to the Western honeybee that has a longer history of domestication, selection on the Asiatic honeybee has favored the generation of more variable antimicrobial peptides as protection against pathogens.
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PMID:Antimicrobial peptide evolution in the Asiatic honey bee Apis cerana. 1915 1

A 5443 Da peptide with sequence homology to defensins was purified from purple pole beans (Phaseolus vulgaris cv. 'Extra-long Purple Pole bean'). This peptide was isolated by adsorption on an affinity chromatographic medium Affi-Gel Blue gel and ion-exchange chromatographic media SP-Sepharose (sulfopropyl-Sepharose) and Mono S and by gel filtration on Superdex peptide. The peptide inhibited mycelial growth in Mycosphaerella arachidicola, Helminthosporium maydis, Fusarium oxysporum, Verticillium dahliae, Rhizoctonia solani, Candida albicans and Setosphaeria turcica with an IC50 of 0.8, 0.9, 2.3, 3.2, 4.3, 4.8 and 9.8 microM respectively. Its antifungal potency was higher than that of the plant defensin coccinin (IC50>50 microM). It induced membrane permeabilization in C. albicans as evidenced by SYTOX Green uptake, but did not affect erythrocyte membrane permeability. It inhibited growth in M. arachidicola by inducing chitin accumulation at hyphal tips as was shown by Congo Red staining. The antifungal activity was pH stable and thermostable. The peptide inhibited the proliferation of hepatoma (HepG2), breast cancer (MCF7), colon cancer (HT29) and cervical cancer (SiHa) cells but not that of human embryonic liver (WRL68) cells. Its anti-HepG2 activity (IC50=4.1+/-0.8 microM, n=3) was higher than that of another plant defensin, gymnin (IC50>50 microM). Its anti-MCF7 activity (IC50=8.3+/-0.3 microM, n=3) was similar to that of other plant defensins. It reduced the activity of HIV-1 reverse transcriptase with an IC50 of 0.5+/-0.1 microM, n=3, much more potently than other plant defensins (IC50>40 microM). There is the possibility of using the purple pole bean defensin for producing antifungal drugs and/or transgenic plants with fungal resistance.
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PMID:A defensin with highly potent antipathogenic activities from the seeds of purple pole bean. 1933 35


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