Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.5.1.3 (dihydrofolate reductase)
 5,819 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A recombinant plasmid containing expression units for human pre-interleukin 2 (pre-IL-2) and the selectable marker mouse DHFR, was constructed and used to transform DHFR- CHO cells to the DHFR+ phenotype. Selected colonies were isolated and tested for IL-2 production. Twelve highly IL-2-producing clones were amplified in stepwise increasing concentrations of methotrexate. The IL-2 secreted into the culture medium by one of these clones was purified to homogeneity and partially characterized. N-terminal sequence analysis showed that pre-IL-2 was correctly processed during secretion. SDS gel electrophoresis and chromatofocusing experiments in conjunction with neuraminidase treatment indicated a posttranslational glycosylation of the secreted mature protein similar to that described for the tetrasaccharide structure of the N2 form of natural IL-2. This recombinant IL-2 has a specific activity of 2.5 x 10(7) U/mg.
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PMID:Characterization of recombinant glycosylated human interleukin 2 produced by a recombinant plasmid transformed CHO cell line. 350 Aug 74

We have established a baby hamster kidney (BHK) cell line that constitutively expresses significant quantities of human recombinant lecithin:cholesterol acyltransferase (rLCAT). LCAT cDNA was cloned into a mammalian expression vector containing the metallothionein promoter and the dihydrofolate reductase gene. After transfection, the BHK cells were treated with 500 microM methotrexate for 2 weeks to select the successfully transfected cells. Surviving colonies were subcloned and high level secretors were identified by measurement of LCAT activity and mass in the culture medium. The attachment of transfected cells to microcarrier beads enabled the efficient production of large quantities of rLCAT in a serum-free medium. After a single-step chromatography procedure, the rLCAT was purified to homogeneity with yields exceeding 1 mg of rLCAT per 100 ml of culture medium. The molecular weight of rLCAT (approximately 66,000) was identical to that of purified human plasma LCAT on SDS polyacrylamide electrophoresis. The rLCAT was activated by apolipoprotein A-I and had an average specific activity that was similar to purified plasma LCAT. After selective deglycosylation with either neuraminidase or N-glycanase, rLCAT and plasma LCAT had identical molecular weights. The simplification of the production and purification of rLCAT reported here will enable a more in depth analysis of the structure and function of this enzyme.
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PMID:Expression and characterization of recombinant human lecithin:cholesterol acyltransferase. 837 Oct 71

A method is presented for enumerating a large number of isosteric analogues of a ligand from a known protein-ligand complex structure and then rapidly calculating an estimate of their binding energies. This approach takes full advantage of the observed crystal structure, by reusing the atomic co-ordinates determined experimentally for one ligand, to approximate those of similar compounds that have approximately the same shape. By assuming that compounds with similar shapes adopt similar binding poses, and that entropic and protein flexibility effects are approximately constant across such an isosteric series ("the frozen ligand approximation"), it is possible to order their binding affinities relatively accurately. Additionally, the constraint that the atomic coordinates are invariant allows for a dramatic simplification in the Poisson-Boltzmann method used to calculation the electrostatic component of the binding energy. This algorithmic improvement allows for the calculation of tens of thousands of binding energies per second for drug-like molecules, enabling this technique to be used in screening large virtual libraries of isosteric analogues. Most significantly, this procedure is shown to be able to reproduce SAR effects of subtle medicinal chemistry substitutions. Finally, this paper reports the results of the proposed methodology on seven model systems; dihydrofolate reductase, Lck kinase, ribosome inactivating protein, L: -arabinose binding protein, neuraminidase, HIV-1 reverse transcriptase and COX-2.
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PMID:Electrostatic evaluation of isosteric analogues. 1684 6

In this study, we propose a drug design approach which includes docking, molecular fingerprints based cluster analysis, and 'induced' descriptors based receptor-dependent 3D-QSAR. The method was shown to be very useful for screening and modeling structurally diverse data sets of pharmacological interest. Different from other receptor-dependent 3D-QSAR, no ambiguous alignments are required for the construction of the models, and the computational cost is relatively lower. Moreover, 'induced' descriptors were shown to be very powerful in "capturing" ligand-receptor intermolecular interactions. The methodology was validated for eight data sets sampled from the literature and from public databases: human sex hormone-binding globulin, human corticosteroid-binding globulin, anthrax lethal factor, HIV-1 reverse transcriptase, neuraminidase A, thrombin, trypsin, and Pneumocystis carinii dihydrofolate reductase data sets. The resulting models were interpretable; the constructed QSAR equations have high statistical significance and predictive strength; and the drug design solutions were shown to be useful for guiding ligand modification for the development of new inhibitors for a broad range of molecular targets.
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PMID:Using molecular docking, 3D-QSAR, and cluster analysis for screening structurally diverse data sets of pharmacological interest. 1881 24

Previous studies have shown the usefulness of the substrate envelope concept in the analysis and prediction of drug resistance profiles for human immunodeficiency virus protease mutants. This study tests its applicability to several other therapeutic targets: Abl kinase, chitinase, thymidylate synthase, dihydrofolate reductase, and neuraminidase. For the targets where many (> or =6) mutation data are available to compute the average mutation sensitivity of inhibitors, the total volume of an inhibitor molecule that projects outside the substrate envelope V(out), is found to correlate with average mutation sensitivity. Analysis of a locally computed volume suggests that the same correlation would hold for the other targets, if more extensive mutation data sets were available. It is concluded that the substrate envelope concept offers a promising and easily implemented computational tool for the design of drugs that will tend to resist mutations. Software implementing these calculations is provided with the 'Supporting Information'.
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PMID:Toward the design of mutation-resistant enzyme inhibitors: further evaluation of the substrate envelope hypothesis. 1970 25

Ensembles of protein structures to simulate protein flexibility are widely used throughout several applications including virtual lead optimization where they have been shown to improve ligand ranking. Yet, there is no established convention for weighting individual scores generated from ensemble members. To investigate the best method for weighting ensemble scores for proper ligand ranking, a series of dihydrofolate reductase inhibitors was docked to ensembles of Candida albicans dihydrofolate reductase (CaDHFR) structures created from a molecular dynamics (MD) simulation. From a single MD simulation, two ensemble collections were generated, one of which was subjected to a minimization procedure to create a group of structures of equal probability. As expected, ligand ranking accuracy was significantly improved when Boltzmann weighting was applied to the energies of the ensemble without structural minimization (60%), relative to that achieved with averaging (36%). However, accuracy was further improved (72%) by averaging docking scores across a minimized ensemble. To examine whether this accuracy results from structural variation in the single trajectory versus the possibility that error is minimized by averaging, a third collection of receptor structures was created in which each member was taken from an independent molecular dynamics simulation after minimization. Comparison of the docking accuracy results from the single trajectory (72%) to this third collection (61%) showed decreased accuracy, suggesting that ligands are more accurately oriented and assessed when docked to the minimized ensemble from a single MD trajectory, an effect that is more than simply error minimization. Averaging docking scores over a minimized ensemble of another target, influenza A neuraminidase, yielded a ligand ranking accuracy of 83%, representing a 24% improvement over other methods tested.
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PMID:Scoring ensembles of docked protein:ligand interactions for virtual lead optimization. 1995 Sep 79

Enzymes are often excellent drug targets. Yet drug pressure on an enzyme target often fosters the rise of cells with resistance-conferring mutations, some of which may compromise fitness and others that compensate to restore fitness. This review presents, first, a structural analysis of a diverse group of wild-type and mutant enzyme targets and, second, an in-depth analysis of five diverse targets to elucidate a broader perspective of the effects of resistance-conferring mutations on protein or organismal fitness. The structural analysis reveals that resistance-conferring mutations may introduce steric hindrance or eliminate critical interactions, as expected, but that they may also have indirect effects such as altering protein dynamics and enzyme kinetics. The structure-based development of the latest generation of inhibitors targeting HIV reverse transcriptase, P. falciparum and S. aureus dihydrofolate reductase, neuraminidase, and epithelial growth factor receptor (EGFR) tyrosine kinase, is highlighted to emphasize lessons that may be applied to future drug discovery to overcome mutation-induced resistance. Successful next-generation drugs tend to be more flexible and exploit a greater number of interactions mimicking those of the substrate with conserved residues.
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PMID:Winning the arms race by improving drug discovery against mutating targets. 2205 Mar 47