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

---

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

Transcription-translation coupled systems have been developed to study prokaryotic gene expression. Several types of expression system have been described. The original system consists of a crude unfractionated Escherichia coli extract, which supports protein synthesis directed by a template DNA. Control of gene expression at the transcriptional stage has been studied using this unfractionated system. In this respect, two examples of particular interest, lactose and tryptophan operons, are described. Other systems are either partially reconstituted or highly defined, containing up to 30 purified factors necessary for transcription (RNA polymerase) and translation (aminoacyl-tRNA synthetases, initiation, elongation and release factors). Additional differences between the various systems relate to the analysis of the gene products. Whereas most methods involve analysis of the totally synthesized protein, a particular system implies the formation of only the N-terminal di- or tripeptide of the gene product. Reconstituted systems have proved useful in studies on transcriptional, e.g., discovery and role of L factor, as well as translational regulation of gene expression, e.g., autogenous control of ribosomal protein synthesis.
...
PMID:Prokaryotic gene expression in vitro: transcription-translation coupled systems. 309 Oct 86

The nucleotide sequence (25,320 base-pairs) of a part of the large single-copy region of chloroplast DNA from the liverwort Marchantia polymorpha was determined. This region encodes putative genes for four tRNAs, isoleucine tRNA(CAU), arginine tRNA(CCG), proline tRNA(UGG) and tryptophan tRNA(CCA); eight photosynthetic polypeptides, the large subunit of ribulose bisphosphate carboxylase/oxygenase (rbcL), 51,000 Mr photosystem II chlorophyll alpha apoprotein (psbB), apocytochrome b-559 polypeptides (psbE and psbF), 10,000 Mr phosphoprotein (psbH), cytochrome f preprotein (petA), cytochrome b6 polypeptide (petB), and cytochrome b6/f complex subunit 4 polypeptide (petD); 13 ribosomal proteins (L2, L14, L16, L20, L22, L23, L33, S3, S8, S11, S12, S18 and S19); initiation factor 1 (infA); ribosome-associating polypeptide (secX); and alpha subunit of RNA polymerase (rpoA). Functionally related genes were located in several clusters in this region of the genome. There were two ribosomal protein gene clusters: rpl23-rpl2-rps19-rpl22-rps3-rpl16-+ ++rpl14-rps8-infA-secX-rps11-rpoA, with a gene arrangement similar to that of the Escherichia coli S10-spc-alpha operons, and the rps12'-rpl20-rps18-rpl33 cluster. There were gene clusters encoding photosynthesis components such as the psbB-psbH-petB-petD and the psbE-psbF clusters. Thirteen open reading frames, ranging in length from 31 to 434 amino acid residues, remain to be identified.
...
PMID:Structure and organization of Marchantia polymorpha chloroplast genome. III. Gene organization of the large single copy region from rbcL to trnI(CAU). 319 36

We have characterized the functional attributes of a 211-base pair region containing the Escherichia coli tryptophan operon rho-dependent terminator trp t', utilizing a series of constructs that alter the orientation, location, or extent of the trp t' sequences with respect to the trp promoter. In each instance, the extent of the rho-dependent response was monitored in vivo by read-through expression into a distal galactokinase gene and was compared with the results of transcription assays in vitro. As expected, transcription termination in vivo is dependent on the proper orientation of the terminator, and a tandem repeat of the terminator increases termination proportionally. Placing the terminator fragment only 14 nucleotides from the promoter does not affect termination significantly, supporting the belief that sequences outside of the 211-base pair fragment itself are dispensable. One construct, which lacks 116 base pairs, including the region encoding the normal RNA end points, still reduces galK activity in vivo and terminates transcription in vitro. Our results indicate that the rho response depends primarily on sequences in this 95-base pair segment, causing RNA polymerase to terminate transcription in a region 15-45 nucleotides further downstream.
...
PMID:Signals sufficient for rho-dependent transcription termination at trp t' span a region centered 60 base pairs upstream of the earliest 3' end point. 327 76

Analogs of amaninamide, due to the absence of a 6-hydroxy group in the tryptophan moiety, are more easily accessible by synthesis than derivatives of alpha-amanitin. Syntheses of bicyclic octapeptide thioethers 1f-1m have been carried out starting from linear Hpi-S-trityl-octapeptides (3), cyclization by intramolecular 2'-indolylthioether formation yielding monocyclic peptides (2) and final cyclization by DCCI. One of the bicyclic thioethers was oxidized to yield the corresponding chromatographically separated (R)- and (S)-sulfoxides, respectively. The products were characterized by RF-values, u.v. and CD spectra as well as by mass (FAB) spectroscopy. The widely differing inhibitory activities on RNA polymerase II (or B) from calf thymus are listed.
...
PMID:Synthesis of analogues of amaninamide, an amatoxin from the white Amanita virosa mushroom. 342 28

Escherichia coli K-12 strain 285c contains a mutation in rpoD, the gene encoding the sigma subunit of RNA polymerase. The 70-kilodalton sigma polypeptide encoded by this allele is unstable, and this instability leads to temperature-sensitive growth. We describe the isolation and characterization of four temperature-resistant pseudorevertants of 285c that can grow at high temperature. Each of these revertants increased the stability of the sigma 70 mutant protein. The map position of the suppressor mutations was close to that of the rpoH (htpR) gene. A multicopy plasmid containing the intact rpoH gene restored the temperature-sensitive phenotype. Marker rescue experiments established the positions of three of the alleles within the rpoH gene. One mutation has been sequenced and causes a leucine-to-tryptophan change 7 amino acids from the carboxyl terminus of the rpoH gene product.
...
PMID:Mutations in the rpoH (htpR) gene of Escherichia coli K-12 phenotypically suppress a temperature-sensitive mutant defective in the sigma 70 subunit of RNA polymerase. 388 72

Fusidic acid or chloramphenicol was used to inhibit peptide synthesis to 1% of normal in Escherichia coli B, strain AS19. After 10 min of inhibition, peptide synthesis could be quickly restored to 80% of the normal rate after washing the bacteria on a filter. However, even in the presence of adenosine 3'-5'-cyclic-monophosphoric acid to block catabolite repression, beta-galactosidase, the first enzyme of the lactose operon (lac), could only be induced to 10% of normal, and the last enzyme of the operon, galactoside acetyltransferase, even less. The first and last enzymes of the operon for tryptophan synthesis could be derepressed to about 30% of normal. The lac ribonucleic acid (RNA) induced during recovery showed a smaller than normal size distribution on sucrose gradients. The operator-proximal or -distal parts of this RNA were specifically labeled. Hybridization to phi80dlac deoxyribonucleic acid (DNA) suggested that although the distal parts of the lac RNA were barely detectable, initiation was occurring at normal rates in recovery. Either normal levels of distal messenger RNA (mRNA) are made but then rapidly degraded or the mRNA is not completed. The small amount that is made decayed abnormally slowly, probably as a result of slower transcription. Total mRNA decay was multiphasic with all components decaying slower than normal. We propose that there is a residual level of inhibition of peptide synthesis during recovery. The probability that a ribosome is blocked at any codon can be estimated from the data. The longer the message, the less likely its complete translation. We propose that the RNA polymerase can transcribe translatable mRNA for only a finite distance beyond the lead ribosome. Because ribosomes can load at the start of each message in a polycistronic mRNA, the probability that a distal message will be synthesized and translated is a function of the number of more proximal messages and the distances between their ribosome-loading sites.
...
PMID:Residual polarity and transcription-translation coupling during recovery from chloramphenicol or fusidic acid. 435 50

1. The perturbing effect of glycerol on the direct spectrum of Escherichia coli DNA-dependent RNA polymerase has been studied. 2. By comparison with model compounds and with the unfolded polymerase in 3.8m-urea it was possible to determine the ratio of tyrosine and tryptophan residues present. On reduction of the urea-treated enzyme with 2-mercaptoethanol, no further change in the difference spectrum occurred. 3. The amino acid composition of the enzyme is given. 4. In the intact protein approx. 30% of the tryptophan and 54% of the tyrosine residues were exposed. In conjunction with the extinction value and molecular weight this corresponded to 7 tryptophan residues and 57 tyrosine residues on the surface and 16 tryptophan residues and 48 tyrosine residues ;buried'. 5. The optical rotatory dispersion of the enzyme was unaffected by 20% glycerol. 6. The helix content calculated from Moffit plots over 560-300nm was 13%, and from the 233nm trough 13%.
...
PMID:Location of aromatic amino acids and belix content in Escherichia coli ribonucleic acid polymerase. 494 33

Bacterial mutants have been isolated, called groN, that block phage development by interference with the action of the product of the phage N gene. lambdatrp phages, which depend on the N product for the synthesis of tryptophan enzymes, do not make these enzymes in groN bacteria. Two type of phage mutants have been isolated that can overcome the groN block. One type makes an altered N product, the other contains an N-bypass mutation. The groN mutation is closely linked to the rifamycin-resistance locus in Escherichia coli. Purified RNA polymerase from the groN mutant is less activated by salt and more sensitive to rifamycin than is the polymerase from gro(+). This suggests that the groN mutation produces a structural change in the bacterial RNA polymerase such that it can no longer interact properly with the phage N product.
...
PMID:Bacterial mutants in which the gene N function of bacteriophage lambda is blocked have an altered RNA polymerase. 494 50

In an attempt to understand the nature of cytoplasmic and nuclear enlargement of liver cells designated as megalocytosis that results from chronic poisoning by lasiocarpine, a pyrrolizidine alkaloid, certain functional aspects of these cells were investigated together with the study of their morphology. The RNA polymerase activity of the megalocyte nuclei was essentially comparable to the activity observed in normal liver cells. Further, the inducibility of tryptophan pyrrolase activity by hydrocortisone, in the livers of rats treated chronically with lasiocarpine is an indication that translational mechanisms are intact. However, the increased uptake of 3H-thymidine by megalocytes, in the absence of observable mitotic activity, suggests that these cells are in the process of hypertrophy. It is concluded that the megalocytes are functionally normal cells, except that they are in the process of cellular hypertrophy and are incapable of division due to potent antimitotic action of the pyrrolizidine alkaloids.
...
PMID:Hepatic megalocytosis in chronic lasiocarpine poisoning. Some functional studies. 513 90

1. The Widnell & Tata (1966) assay method for Mg(2+)-activated DNA-dependent RNA polymerase was used for initial-velocity determinations of rat liver nuclear RNA polymerase. One unit (U) of RNA polymerase was defined as that amount of enzyme required for 1 mmol of [(3)H]GMP incorporation/min at 37 degrees C. 2. Colony fed rats were found to have a mean RNA polymerase activity of 65.9muU/mg of DNA and 18h-starved rats had a mean activity of 53.2muU/mg of DNA. Longer periods of starvation did not significantly decrease RNA polymerase activity further. 3. Rats that had been starved for 18h were used for all feeding experiments. Complete and tryptophan-deficient amino acid mixtures were given by stomach tube and the animals were killed 15-120min later. The response of RNA polymerase to the feeding with the complete amino acid mixture was rapid and almost linear over the first hour of feeding, resulting in a doubling of activity. The activity was still elevated above the starvation value at 120min after feeding. The tryptophan-deficient amino acid mixture produced a much less vigorous response about 45min after the feeding, and the activity had returned to the starvation value by 120min after the feeding. 4. The response of RNA polymerase to the feeding with the complete amino acid mixture was shown to occur within a period of less than 5min to about 10min after the feeding. 5. Pretreatment of the animals with puromycin or cycloheximide was found to abolish the 15min RNA polymerase response to the feeding with the complete amino acid mixture, but the activity of the controls was unaffected. 6. The characteristics of the RNA polymerase from 18h-starved animals and animals fed with the complete or incomplete amino acid mixtures for 1h were examined. The effects of Mg(2+) ions, pH, actinomycin D and nucleoside triphosphate omissions were determined. The [Mg(2+)]- and pH-activity profiles of the RNA polymerase from the animal fed with the complete mixture appeared to differ from those of the enzyme from the other groups, but this difference is probably not significant. 7. [5-(3)H]Orotic acid incorporation by rat liver nuclei in vivo was shown to be affected by the amino acid mixtures in a similar manner to the RNA polymerase. 8. The tryptophan concentrations of plasma and liver were determined up to 120 min after feeding with the amino acid mixtures. Feeding with the complete mixture produced a rapid increase in free tryptophan concentrations in both plasma and liver, but feeding with the incomplete mixture did not alter the plasma concentration. The liver tryptophan concentration increased at about 45min after feeding with the tryptophan-deficient diet. 9. There was a good correlation between the liver tryptophan concentration and RNA polymerase activity in all groups of animals. 10. It was concluded that the rat liver nucleus responded to an increase in amino acid supply by increased synthesis of RNA as a result of synthesis of RNA polymerase de novo. The correlation of tryptophan concentration and RNA polymerase activity appears to reflect the general amino acid concentration required to support hepatic protein synthesis and to produce new RNA polymerase. This new polymerase appears to differ from the basal RNA polymerase by its rapid synthesis and destruction, which may be a means of regulating RNA synthesis by the amino acid concentration in the liver.
...
PMID:The effect of feeding with a tryptophan-free amino acid mixture on rat liver magnesium ion-activated deoxyribonucleic acid-dependent ribonucleic acid polymerase. 549 25


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---