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)

TSAO derivatives represent a class of nonnucleoside reverse transcriptase inhibitors (NNRTIs) that consistently select for the Glu138Lys resistance mutation in HIV-1 reverse transcriptase (RT). Seven RT mutants (i.e., Ala, Asp, Gln, Gly, Lys, Phe, and Tyr) were constructed by site-directed mutagenesis. The mutant Glu138Asp, Glu138Lys, Glu138Gln, Glu138Ala, and Glu138Gly RTs retained marked catalytic activity. In contrast, the Glu138Phe and Glu138Tyr RT mutants showed poor RNA-dependent DNA polymerase activity (30 and 4% of wild-type, respectively). TSAO derivatives lost their inhibitory activity against all mutant enzymes, except against the closely related Glu138Asp RT mutant that remained as sensitive to TSAOs as did wild-type RT. Other NNRTIs, including delavirdine, emivirine, and UC-781, and the NRTI ddGTP retained pronounced inhibitory activity against all mutant enzymes. When the amino acid mutations at position 138 of RT were introduced in recombinant virus clones, the sensitivity/resistance spectrum obtained toward the TSAOs and other NNRTIs was similar to those observed for the isolated recombinant mutant enzymes. The Glu138Lys RT mutant virus had the most marked resistance to TSAOs, followed by the Glu138Gln, Glu138Phe, Glu138Gly, Glu138Tyr, and Glu138Ala virus mutants. The Glu138Asp RT mutant virus kept full sensitivity to the TSAO derivatives. Mixtures of Glu138Lys RT mutant virus with the other virus clones mutated at the 138 position resulted in all cases, except for the Glu138Asp and Glu138Gly RT mutant viruses, in an outgrowth of the Glu138Lys RT mutant virus. Since the Glu138Lys RT proved most resistant to TSAO derivatives, was among the most catalytically efficient enzymes, and resulted in highly replication-competent virus, our data explain why the Glu138Lys RT mutant virus strains but not virus strains containing other amino acids at position 138 invariably emerge in cell cultures under TSAO drug pressure.
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PMID:Site-directed mutagenesis of human immunodeficiency virus type 1 reverse transcriptase at amino acid position 138. 1116 23

Sheep immunoglobulin (Ig) heavy-chain (V(H)DJ(H)) and lambda light-chain variable region (V(lambda)J(lambda)) nucleotide coding sequence was isolated by reverse transcriptase-polymerase chain reaction (RT-PCR) from abomasal lymph node (ALN) B cells of immune sheep challenged with the gastrointestinal nematode parasite Haemonchus contortus. Single-chain antibodies (scFv) were then constructed with the purified V(H)DJ(H) and V(lambda)J(lambda) Ig gene region DNA using oligonucleotides to PCR and join the variable regions to a central [Gly(4)Ser](3)-linker. In a similar fashion 5'-SfiI and 3'-NotI restriction endonuclease sites were added for cloning into a phagemid expression vector. Expression of sheep scFv from pHFA phagemid in an amber-suppresser strain of Escherichia coli, after infection with filamentous phage, resulted in 10(9) sheep scFv antibodies displayed as a library on phagemid particles. Western blot analysis demonstrated sheep scFv gene expression in E. coli cell lysate and on purified library phage. In addition, four rounds of scFv-library selection against H. contortus surface antigen resulted in a 300-fold increase in the elution titre of phage recovered from parasite surface antigen. Nearly 1000 of the selected and eluted scFvs were expressed in an attempt to identify monoclonal sheep scFv against parasite antigen. Only low affinity clones were isolated during screening of this sheep scFv-library, suggesting different strategies will be needed for isolation of specific high affinity recombinant antibody in future studies.
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PMID:A single-chain variable region immunoglobulin library from the abomasal lymph node of sheep infected with the gastrointestinal nematode parasite Haemonchus contortus. 1118 52

The potential roles of an amino acid deletion at codon 67 (Delta67) and a Thr-to-Gly change at codon 69 (T69G) in the reverse transcriptase of human immunodeficiency virus (HIV) type 1 in drug sensitivity and relative replication fitness were studied. Our results suggest that the Delta67 and T69G changes can be categorized as mutations associated with multidrug resistance. The combination of both mutations with an L74I change (Delta67+T69G/L74I) leads to a novel 3'-azido-3'-deoxythymidine resistance motif and compensates for impaired HIV replication.
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PMID:Amino acid deletion at codon 67 and Thr-to-Gly change at codon 69 of human immunodeficiency virus type 1 reverse transcriptase confer novel drug resistance profiles. 1126 89

Phytic acid, a phosphorylated derivative of myo-inositol, functions as the major storage form of phosphorus in plant seeds. Myo-inositol phosphates, including phytic acid, play diverse roles in plants as signal transduction molecules, osmoprotectants, and cell wall constituents. D-myo-inositol-3-phosphate synthase (MIPS EC 5.5.1.4) catalyzes the first step in de novo synthesis of myo-inositol. A soybean (Glycine max) MIPS cDNA (GmMIPS1) was isolated by reverse transcriptase-PCR using consensus primers designed from highly conserved regions in other plant MIPS sequences. Southern-blot analysis and database searches indicated the presence of at least four MIPS genes in the soybean genome. Northern-blot and immunoblot analyses indicated higher MIPS expression and accumulation in immature seeds than in other soybean tissues. MIPS was expressed early in the cotyledonary stage of seed development. The GmMIPS1 expression pattern suggested that it encodes a MIPS isoform that functions in seeds to generate D-myo-inositol-3-phosphate as a substrate for phytic acid biosynthesis.
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PMID:Expression of D-myo-inositol-3-phosphate synthase in soybean. Implications for phytic acid biosynthesis. 1129 73

Thai bitter gourd protein (MRK29) was isolated from Momordica charantia ripe fruit and seed. The purification was performed by ammonium sulfate fractionation and gel filtration chromatography. MRK29 possessed one isoelectric point of (pI) > or = 9, and the time of flight mass spectrum (TOFMS) indicated its molecular weight at 28.6 kD. The twenty amino acid sequence from the N-terminus was in the following order: 1Asp Val Asn Phe Arg Leu Ser Gly Ala 10Asp Pro Arg X Tyr Gly Met Phe Ile Glu 20Asp. MRK29 inhibited the HIV-1 reverse transcriptase with 50% IR at the concentration of 18 micrograms/ml. MRK29 was concentrated in the 30-60% salt precipitated fraction, at which the concentration of 0.175 microgram/ml exerted 82% reduction of viral core protein p24 expression in HIV-infected cells. MRK29 might have modulatory role on immune cells, because it increased 3-fold TNF activity.
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PMID:HIV inhibitor from Thai bitter gourd. 1145 53

To identify neural tumor cell lines that could be used as models to study growth-related natriuretic peptide actions, we determined the effects of these peptides on the proliferation of human and rodent neuroblastoma cell lines. Subnanomolar concentrations of atrial natriuretic peptide (ANP) and type C natriuretic peptide (CNP) stimulated proliferation in all four cell lines. These actions were associated with cGMP elevation and were blocked by a protein kinase G inhibitor. These data imply the involvement of guanylyl cyclase (GC)-coupled natriuretic receptors. However, higher concentrations of ANP and CNP, and low concentrations of des-[Gln(18),Ser(19),Gly(20),Leu(21),Gly(22)]-ANP(4-23)-NH(2) (desANP(4-23)) (analog for NPR-C receptor) exerted antiproliferative actions in three of the cell lines. These effects were insensitive to a protein kinase G inhibitor and to HS-142-1, suggesting that growth-inhibitory actions involved a non-GC receptor. They did not appear to involve cAMP, protein kinase A, protein kinase C, or calcium mobilization but were abolished when constitutive mitogen-activated protein kinase activity was inhibited. Radioligand binding experiments revealed the presence of a uniform class of binding sites in NG108 cells and multiple binding sites in Neuro2a cells. Northern and reverse transcriptase-polymerase chain reaction analyses revealed differential gene expression for NPR-A/B/C in NG108 and Neuro2a cells. The results indicate that natriuretic peptides stimulate neuroblastoma cell proliferation through type NPR-A/B (GC) receptors. Higher concentrations of ANP and CNP exerted a mitogen-activated protein kinase-dependent antiproliferative action mediated by a non-GC receptor that interacts with desANP(4-23) with relatively high affinity.
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PMID:Proliferative actions of natriuretic peptides on neuroblastoma cells. Involvement of guanylyl cyclase and non-guanylyl cyclase pathways. 1155 33

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

The cockroach-type or A-type allatostatins are inhibitory insect neuropeptides with the C-terminal sequence Tyr/Phe-X-Phe-Gly-Leu-NH(2). Here, we have cloned an A-type allatostatin receptor from the silkworm Bombyx mori (BAR). BAR is 361 amino acid residues long, has seven transmembrane domains, shows 60% amino acid residue identity with the first Drosophila allatostatin receptor (DAR-1), and 48% identity with the second Drosophila allatostatin receptor (DAR-2). The BAR gene has two introns and three exons. These two introns coincide with and have the same intron phasing as two introns in the DAR-1 and DAR-2 genes, showing that the three receptors are not only structurally but also evolutionarily related. Furthermore, we have cloned a Bombyx allatostatin preprohormone that contains eight different A-type allatostatins. Chinese hamster ovary cells permanently transfected with BAR DNA react on the addition of 4 x 10(-9)M Bombyx A-type allatostatins with a second messenger cascade (measured as bioluminescence), showing that BAR is a functional A-type allatostatin receptor. Southern blots suggest that Bombyx has at least one other BAR-related gene in addition to the BAR gene described in this paper. Northern blots and quantitative reverse transcriptase-polymerase chain reaction of different larval tissues show that BAR mRNA is mainly expressed in the gut and to a much lesser extent in the brain. To our knowledge, this is the first report on the molecular cloning and functional expression of an insect gut/brain peptide hormone receptor.
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PMID:Molecular cloning of a functional allatostatin gut/brain receptor and an allatostatin preprohormone from the silkworm Bombyx mori. 1159 Jan 50

Twenty distinct genetic types of collagen have been identified up to now. Their structure and function are not completely elucidated. We have chosen zebrafish as a model to bring information about the role of collagen during embryogenesis. In the present study, we isolated four overlapping DNA complementary to RNA clones covering the 4879 nucleotides of a zebrafish messenger RNA (mRNA) encoding a fibrillar procollagen chain. The comparison of its primary structure with known other vertebrate collagens allowed to conclude that it encodes collagen pro-alpha2(I) chain. The 5' untranslated region showed a typical stem-loop structure with three ATG codons which is found in mammals types I and III collagen chains (but not in type II), which are expressed in the same tissues. This suggests that the supposed regulatory role of the stem loop structure could be tissue specific. The comparison of the Gly-Gly doublets found along the helical domain of several species allowed to speculate that the Gly-Gly repeats could be a poikilotherm feature. Expression of pro-alpha2(I) was examined during zebrafish development by reverse transcriptase-polymerase chain reaction and in situ hybridization on whole embryo and tissue section. Col1a2 was expressed as early as stage10 h post fertilization (hpf) and two peaks of expression were observed at 20 and 48 hpf. alpha2 mRNAs, whose presence suggests a collagen synthesis, were detected principally in the superficial cell layers surrounding 20-72 hpf embryos which are characterized by an acellular collagen stratum. At 26-30 days, fibroblasts invade the dermis and take over from the epithelial cells to synthesize collagen. This suggests a fine regulation of collagen synthesis in these cells that remains to be elucidated. alpha2 mRNA were also detected in other tissues such as the tail fin primordium and the notochord primordium suggesting a participation of type I collagen in a pathway for notochord and tail formation.
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PMID:Structure and spatio temporal expression of the full length DNA complementary to RNA coding for alpha2 type I collagen of zebrafish. 1223 67

SIRE1 is unusual among Ty1-copia retrotransposons in that it has an additional open reading frame with structural features similar to retroviral envelope proteins between pol and the 3' LTR. Here we report the characterization and comparison of eight different SIRE1 elements derived from a soybean genomic library, as well as SIRE1 reverse transcriptases from Glycine soja. The DNA sequences of the eight SIRE1 elements are highly homogeneous and share greater than 95% nucleotide identity. Partial sequences obtained from BAC ends are similarly conserved. Phylogenetic analyses resolve two closely related SIRE1 lineages, and nucleotide changes within and between SIRE1 lineages have occurred to preserve function. Both the gag and the env-like genes are evolving under similar levels of functional constraint. Considerable sequence heterogeneity in the form of short duplications was found within the LTRs and in the region between the envelope-like ORF and the 3' LTR. These duplications are suggestive of slippage by reverse transcriptase during replication. Sequence identity between LTRs of individual insertions suggests that they transposed within the past 70,000 years. Two of 10 SIRE1 insertions examined abut Ty3-gypsy retroelements. Since the soybean genome harbors more than 1,000 SIRE1 insertions, the collective data suggest that SIRE1 has undergone a very recent and robust amplification in soybean.
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PMID:SIRE1, an endogenous retrovirus family from Glycine max, is highly homogeneous and evolutionarily young. 1277 3


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