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:2.7.7.6 (RNA polymerase)
34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The nicotinic acetylcholine (AcCho) receptor (AcChoR) is a multisubunit protein complex of stoichiometry alpha 2 beta gamma delta. The several subunits show homology with each other within a given species; in addition, homology is found between analogous subunits between species. We have used the phage SP6 RNA polymerase transcription system to produce single-species RNA in vitro for various AcChoR subunits from cDNAs. Injection of an equimolar mixture of RNA for the alpha, beta, gamma, and delta subunits of Torpedo californica AcChoR into Xenopus oocytes results in the appearance of functional receptors in the oocyte membrane. No response to AcCho is detected when the beta or gamma subunit RNA is omitted, and a small response is seen when the delta subunit RNA is omitted. Replacement of Torpedo delta subunit RNA by the mouse BC3H-1 cell line AcChoR delta subunit RNA leads to the formation of functional receptors that show a 3-4-fold greater response to AcCho than does the full Torpedo complex. No response is seen when the mouse delta RNA replaces Torpedo gamma RNA. By amino acid homology profile comparisons, the mouse delta subunit appears to be moderately but not highly similar to the Torpedo delta subunit; the apparent similarity to the Torpedo gamma subunit is only slightly less. Therefore, the features of the primary sequence that determine the functional delta character of the mouse polypeptide are not revealed by simple homology comparisons.
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PMID:Mouse-Torpedo hybrid acetylcholine receptors: functional homology does not equal sequence homology. 386 Aug 26

Fourteen streptovaricin derivatives were tested for inhibition of cellular nucleotide polymerases (deoxyribonucleic acid polymerases alpha, beta, and gamma, terminal deoxynucleotidyltransferase [TdT], and ribonucleic acid polymerase II), simian sarcoma virus deoxyribonucleic acid polymerase, and herpes simplex virus type 1-induced deoxyribonucleic acid polymerase (HSV-DP). Three compounds (strep-tovadienal C, prestreptovarone, and streptoval Fc) preferentially inhibited TdT and HSV-DP over the other enzymes. These compounds inhibited HSV-DP more potently than they inhibited TdT. Evidence indicated that the mode of inhibition of TdT and HSV-DP by streptovadienal C and prestreptovarone was by interaction with the enzymes and not with template-primer, initiator, substrates, or divalent cations required for enzyme activity. Furthermore, data suggested that these compounds bind with greater affinity to HSV-DP than to TdT. Streptovadienal C and prestreptovarone were examined for their effect on the replication of herpes simplex virus type 1 in African green monkey kidney (CV1) cells. These compounds produced 2- and 3-log drops in virus titer, respectively, at concentrations not significantly affecting cell viability. This correlated with evidence indicating a greater binding affinity of these compounds for HSV-DP over cellular nucleotide polymerases.
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PMID:Inhibition of cellular and virus-associated nucleotide polymerases by, and anti-herpes simplex virus activity of, streptovaricin derivatives. 611 56

A model for the quaternary structure of Escherichia coli RNA polymerase (nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6) is presented. It is based on results from classification of profiles of enzyme molecules, and from application of immuno electron microscopy. Classification of molecules, prepared with the single carbon layer technique, was first achieved for images recorded in dark field with the scanning transmission electron microscope and later on for images recorded in bright-field transmission electron microscopy. It results in five approximately equally sized groups, containing about 80% of the core enzyme profiles. Holoenzyme profiles can be grouped into the same classes, and have approximately the same dimensions (9 nm X 16 nm). Based on the shapes and sizes of the classified profiles, a tentative model for core enzyme has been constructed. Correlation of shadow projections of this model, with the distributions of attachment sites of antibodies against alpha, beta, beta' and sigma over the profiles, has led to models for core and holoenzyme in which the subunits are localized. The model is compared with literature data on the quaternary structure of RNA polymerase.
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PMID:The quaternary structure of Escherichia coli RNA polymerase studied with (scanning) transmission (immuno)electron microscopy. 635

The relative rates of RNA polymerase biosynthesis in Bacillus subtilis has been examined under steady-state growth conditions. The synthesis of RNA polymerase subunits (alpha, beta, beta', omega) has been followed by subunit fractionation of immunoprecipitated [3H]-labelled samples on SDS-polyacrylamide gels. The stoichiometries of alpha:beta:beta':omega subunits have been determined from cultures pulse-labelled during steady-state growth. The results suggest that an unassembled pool of the alpha-subunit exists from which the holoenzyme is formed. Upon shift-up from acetate to glycerol containing medium, a rapid rise in the differential rate of core enzyme synthesis was observed, while the rate of synthesis of the alpha-subunit was not stimulated. During shift-down, a concomitant reduction in the rate of synthesis of all subunits occurred for the first 20 min after the shift; thereafter, a rate of synthesis characteristic of the new growth rate was established. As cultures enter sporulation, an immediate reduction in the rate of beta beta'-subunit synthesis was demonstrated.
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PMID:RNA polymerase subunit biosynthesis in Bacillus subtilis. 680 67

Antibodies against the isolated subunits alpha, beta, and beta' of DNA-dependent RNA polymerase from E. coli have been prepared. They have been used to compare the extent of antibody-binding, as measured by complement fixation, to the isolated subunits and to the intact enzyme, in the absence and presence of ligands, such as inhibitors, nucleotides, nucleosides, oligo- and poly-nucleotides, and DNA of different composition. In many cases the results show a subunit-specific dependence of complement fixation upon the presence of a ligand and suggest a functional topography of the interaction between the subunits alpha, beta, and beta' of RNA polymerase and defined nucleotide sequences and small ligands.
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PMID:Antibodies against the subunits of E. coli RNA polymerase as probes for subunit-specific binding of DNA and other ligands. 700 67

In spite of the generally well-coordinated synthesis of RNA polymerase core enzyme subunits (alpha, beta and beta') in Escherichia coli, a situation was found during the growth transition from exponential to stationary phase in which this coordination was broken (the order of differential repression being alpha leads to beta' leads to beta; Kawakami et al. (1979). The present study indicates that, during a certain period of the growth transition, twice as much beta subunit is synthesized as beta' subunit and the overproduced beta subunit accumulates as the assembly intermediate alpha 2 beta complex, which is rapidly and preferentially degraded. Two independent factors, i.e., carbon source down-shift and oxygen depletion, were examined separately for their influence on the coordinated regulation of the synthesis of RNA polymerase subunits. The depletion of glucose added as a sole carbon source was accompanied by repression of the synthesis of all core enzyme subunits, while under the same conditions the differential rate of sigma subunit synthesis increased. In contrast, the sudden ending of the oxygen supply resulted in specific repression of the synthesis of only beta and beta' subunits but not of sigma and alpha subunits. The latter result may be explained by the autogenous repression of the rpoBC genes by a temporal increase in the amount of unused cytoplasmic RNA polymerase.
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PMID:Biosynthesis of RNA polymerase in Escherichia coli. XII. Noncoordinate synthesis of core enzyme subunits after suppression of cell growth. 704 23

The ability of DNA polymerases (pols) to catalyze the template-directed synthesis of duplex oligonucleotides containing a nonstandard Watson-Crick base pair between a nucleotide bearing a 5-(2,4-diaminopyrimidine) heterocycle (d kappa) and a nucleotide bearing either deoxyxanthosine (dX) or N1-methyloxoformycin B (pi) has been investigated. The kappa-X and kappa-pi base pairs are jointed by a hydrogen bonding pattern different from and exclusive of those joining the AT and GC base pairs. Reverse transcriptase from human immunodeficiency virus type 1 (HIV-1) incorporates dXTP into an oligonucleotide opposite d kappa in a template with good fidelity. With lower efficiency and fidelity, HIV-1 reverse transcriptase also incorporates d kappa TP opposite dX in the template. With d pi in the template, no incorporation of d kappa TP was observed with HIV reverse transcriptase. The Klenow fragment of DNA pol I from Escherichia coli does not incorporate d kappa TP opposite dX in a template but does incorporate dXTP opposite d kappa. Bovine DNA pols alpha, beta, and epsilon accept neither dXTP opposite d kappa nor d kappa TP opposite d pi. DNA pols alpha and epsilon (but not beta) incorporate d kappa TP opposite dX in a template but discontinue elongation after incorporating a single additional base. These results are discussed in light of the crystal structure for pol beta and general considerations of how polymerases must interact with an incoming base pair to faithfully copy genetic information.
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PMID:Recognition by viral and cellular DNA polymerases of nucleosides bearing bases with nonstandard hydrogen bonding patterns. 754 38

We present a simple, rapid procedure for reconstitution of Escherichia coli RNA polymerase holoenzyme (RNAP) from individual recombinant alpha, beta, beta', and sigma 70 subunits. Hexahistidine-tagged recombinant alpha subunit purified by batch-mode metal-ion-affinity chromatography is incubated with crude recombinant beta, beta', and sigma 70 subunits from inclusion bodies, and the resulting reconstituted recombinant RNAP is purified by batch-mode metal-ion-affinity chromatography. RNAP prepared by this procedure is indistinguishable from RNAP prepared by conventional methods with respect to subunit stoichiometry, alpha-DNA interaction, catabolite gene activator protein (CAP)-independent transcription, and CAP-dependent transcription. Experiments with alpha (1-235), an alpha subunit C-terminal deletion mutant, establish that the procedure is suitable for biochemical screening of subunit lethal mutants.
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PMID:Rapid RNA polymerase genetics: one-day, no-column preparation of reconstituted recombinant Escherichia coli RNA polymerase. 776 21

The lima bean lectin recognizes terminal alpha-D-GalNAc groups and agglutinates human type A erythrocytes. We have cloned a portion of the gene encoding the alpha subunit of the lima bean lectin. The clone was obtained using the polymerase chain reaction and verified from a genomic clone encoding the mature protein of 253 amino acids. The deduced amino acid sequence has significant overall homology with other leguminous plant lectins and contains all of the known peptide sequences isolated from lima bean lectin (LBL). Southern blot analysis reveals the presence of several genes which hybridize to the cloned gene and which we propose are genes included in the lima bean lectin gene family. We report here the sequence, expression, and characterization of LBL 2, the second member of this gene family. Milligram quantities of soluble active recombinant lima bean lectin (rLBL) were obtained from Escherichia coli, using the T7 RNA polymerase expression system. SDS-polyacrylamide gel electrophoresis and Western blot analysis indicate expression of one protein band of about 27 kDa in induced E. coli cells. This protein cross-reacts with polyclonal antibodies raised against seed lectin (sLBL) and gave a reaction of identity with seed lectin by Ouchterlony double diffusion, specifically agglutinates type A blood cells, and is specifically inhibited by D-GalNAc. The isoelectric point of rLBL is 5.86, whereas those of the seed lectin subunits were determined to be 5.86, 5.58, and 5.20 (previously designated alpha, beta, alpha', respectively). rLBL binds to hydrophobic ligands independent of sugar binding, an observation similar to results obtained with sLBL. However, despite the similar activities described, several significant differences between recombinant and native lima bean lectin were found, including mobility on gel filtration, aggregation in solution, and its CD spectrum. These differences may be due to a number of factors, which will be discussed.
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PMID:The sequence of a second member of the lima bean lectin gene family and the expression and characterization of recombinant lectin in Escherichia coli. 812 94

Plastid genes are transcribed by DNA-dependent RNA polymerase(s), which have been incompletely characterized and have been examined in a limited number of species. Plastid genomes contain rpoA, rpoB, rpoC1, and rpoC2 coding for alpha, beta, beta', and beta" RNA polymerase subunits that are homologous to the alpha, beta, and beta' subunits that constitute the core moiety of RNA polymerase in bacteria. However, genes with homology to sigma subunits in bacteria have not been found in plastid genomes. An antibody directed against the principal sigma subunit of RNA polymerase from the cyanobacterium Anabaena sp. PCC 7120 was used to probe western blots of purified chloroplast RNA polymerase from maize, rice, Chlamydomonas reinhardtii, and Cyanidium caldarium. Chloroplast RNA polymerase from maize and rice contained an immunoreactive 64-kD protein. Chloroplast RNA polymerase from C. reinhardtii contained immunoreactive 100- and 82-kD proteins, and chloroplast RNA polymerase from C. caldarium contained an immunoreactive 32-kD protein. The elution profile of enzyme activity of both algal chloroplast RNA polymerases coeluted from DEAE with the respective immunoreactive proteins, indicating that they are components of the enzyme. These results provide immunological evidence for sigma-like factors in chloroplast RNA polymerase in higher plants and algae.
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PMID:Evidence that sigma factors are components of chloroplast RNA polymerase. 815 91


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