Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

During the course of kinetic studies on the synthesis of RNA polymerase subunits in Escherichia coli K12, strain Km7 (CP372), certain anomalies were found that seemed to be associated with the system of reversible inhibition of RNA and protein synthesis by rifampicin. To find a possible explanation for these anomalies, effects of rifampicin on RNA chain elongation and on residual synthesis of polymerase subunits were investigated with several strains including Km7. Examination of mRNA synthesis for the tryptophan operon suggested that RNA chain growth as well as RNA chain initiation is inhibited at high drug concentration (500 mug/ml), wheras RNA chain initiation is inhibited specifically at low concentration (20 mug/ml). Analysis of effect of rifampicin concentration on total RNA synthesis gave results that are also consistent with this conclusion. These results emphasize the need for selecting a proper drug concentration whenever rifampicin or other related antibiotic is used as a specific inhibitor of transcription initiation. When rifampicin was added to a culture of these strains absolute rates of synthesis of all subunits of RNA polymerase increased for several minutes and then decreased. The extent of this transient stimulation varied depending on the strain, drug concentration and other conditions, but was most striking for the beta and sigma subunits with strain Km7 at high drug concentration (500 mug/ml). With a rifampicin-sensitive wild-type strain tested, the maximum stimulation was found at about 50 mug/ml of the drug, with a particularly marked effect for sigma subunit. Streptolydigin, on the other hand, inhibited the synthesis of core subunits much faster than the bulk of protein, but inhibited synthesis of sigma subunit only after a lag. Hence a specific effect of rifampicin but not the inactivation of beta subunit per se appears to be involved in transient stimulation of polymerase synthesis observed. Implications of these findings on the control of RNA polymerase synthesis are discussed.
Mol Gen Genet 1976 Jun 15
PMID:Effects of rifampicin on synthesis and functional activity of DNA-dependent RNA polymerase in Escherichia coli. 78 14

Mutagenesis of Escherichia coli K12 cells with ethyl methanesulfonate and selection of streptomycin-resistant mutants after a long delay for phenotypic expression allowed us to isolate new types of streptomycin-resistant ribosomes. Misreading patterns of the ribosomes in the presence of streptomycin revealed that most of the streptomycin-resistant mutants isolated under these conditions differed from the four classical types of streptomycin-resistant mutants studied and characterized by Strigini, P. and Gorini, L. (1970) J. Mol. Biol. 47, 517-530.
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PMID:New types of streptomycin-resistant mutants of Escherichia coli. 78 40

In this paper are studied in E. coli K12 the influence of the bacterial Rec and phage mu Red recombination systems on the rescue of the O plus gene from the prophage by a superinfecting O minus phage, UV irradiated or not. In the absence of UV irradiation the Red system produces more recombinants than does the Rec system, and its action requires DNA replication. The presence of UV lesions in the mu DNA facilitates the action of the Rec system, which is more efficient in this instance than the Red system and can act in the absence of DNA replication. In all cases, there is a cooperation between the two generalized recombination systems.
Mol Gen Genet 1976 Jul 05
PMID:Role of the bacterial and phage recombination systems and of DNA replication in genetic recombination of UV-irradiated phage Lambda. 78 9

Escherichia coli K12 Hfr H Tsxs Strs and F- Pro- Tsxr His- Arg- Strr bacteria were conjugated in the absence of arginine with or without glucose. The efficiency of conjugation, measured by the frequency of Pro+ and His+ recombinants was not affected. Arginine starvation alone did not affect the tsxs gene expression which occurred in all the zygotes which had received the gene. In contrast, argine and glucose starvation allows tsxs expression only in those zygotes in which the donor gene had been integrated in the genome. As the glucose starvation brings on a destabilization of the messenger RNA synthesized by the F- cells in absence of arginine, the results can be interpreted as follows: the transferred tsxs genes are transitorily expressed in all the zygotes at the unintegrated state. After this transient period, only thsoe genes integrated in the chromosomes of the zygotes continue to be expressed.
Mol Gen Genet 1976 Aug 10
PMID:Effect of glucose starvation on the expression of transferred tsx genes in Escherichia coli K12 zygotes. 78 25

Merodiploids of the type tif-1/F'tif+, constructed in E. coli K12 strain T44(lambda), show that the tif-1 mutation is recessive with respect to induction of phage lambda and thermolability. An additional manifestation of tif-1 expression is increased tolerance to low levels of streptomycin (SM) and chloramphenicol (CM) and this, too, is abolished in the merodiploids.
Mol Gen Genet 1976 Aug 10
PMID:Phenotypic instability in a tif-1 mutant of Escherichia coli. II. Recessiveness of the tif-1 mutation. 78 27

The mutant T44(lambda) of Escherichia coli K12, grown in the presence of adenine, develops an increased tolerance to streptomycin. In cultures grown on streptomycin, the ts character (tif) may temporarily be suppressed but, on further transfer, both the temperature-sensitive phenotype and streptomycin tolerance disappear. In a cell-free system, the relative efficiency of translation of MS2 and poly U messenger RNAs was, respectively, 75 and 50% lower in extracts from cultures grown at 37 degrees with adenine than in extracts from 30 degrees cultures. Similar results were obtained when adenine was added in vitro to an extract from a culture grown at 37 degrees in the absence of adenine, using MS2 RNA as messenger. Moreover, the 37 degrees extracts showed a much lower misincorporation of isoleucine into polyphenylalanine in the poly U system. In addition, the Mg++ concentration required for optimal translational acitvity was higher for the 37 degrees than for the 30 degrees extracts. Extracts from a culture grown in L medium at 37 degrees or from a tif-/F'tif+ merodiploid grown at 37 degrees with adenine behaved similarly to that from the 30 degrees culture when poly U was used as messenger RNA. It is suggested that the tif+ gene product may play a regulatory role in ribosomal function and the pleiotropic nature of the tif-1 mutation could be due to impairment of translational activity augmented by elevated temperature or by adenine.
Mol Gen Genet 1976 Aug 10
PMID:Phenotypic instability in a tif-1 Mutant of Escherichia coli. I. Impairment in ribosomal function. 78 26

We have examined DNA strand breakage, DNA degradation, and the rate of DNA synthesis in lig and lig-recB strains of Escherichia coli K12 incubated in the presence and absence of 3 mug/ml chloramphenicol. Substantial DNA strand breakage and DNA degradation is observed in the lig strain upon growth at 40 degrees C; however, such strand breakage and DNA degradation is not observed in th lig-recB strainl Incubation of the lig strain at 40 degrees C in the presence of 3 mug/ml chloramphenicol reduces the amount of DNA strand breakage and DNA degradation to the level observed in the lig-recB strain. Together, these results demonstrate that exonuclease V (the recBC gene product) is responsible for the increased DNA degradation associated with DNA ligase deficiency.
Mol Gen Genet 1976 Aug 10
PMID:Effect of chloramphenicol and the recB gene product on DNA metabolism in Escherichia coli K12 strains defective in DNA ligase. 78 29

Trimethoprim inhibits dihydrofolate reductase. Mutations conferring trimethorpim-resistance on E coli K12 result in either an altered reductase with decreased affinity for the drug, or in 2-30 fold higher levels of the enzyme. Studies of the latter class of mutants indicate that dihydrofolate reductase is regulatdd by a diffusible molecule, and is probably under negative control. The regulatrory mutants, some of which are temperature-sensitive, act cis.
Mol Gen Genet 1976 Aug 10
PMID:Regulatory mutants of dihydrofolate reductase in Escherichia coli K12. 78 30

Various Escherichia coli strains differ in the composition of their major outer membrane proteins. However, all E. coli K12 strains tested possess the same major outer membrane proteins a, b, c and d, although quantitative differences were detected. The influence of growth conditions on the composition of the major outer membrane proteins of E. coli was analyzed. It was found that neither the growth phase at which the cells are harvested, nor the fatty acid composition of the phospholipids has a considerable influence on the composition of these proteins. However, the composition of the growth medium, and, to a less extent, the growth temperature, have a pronounced influence. Certain mutants, changed in the composition of their lipopolysaccharide, are deficient in protein b. Also mutants deficient in protein c and d respectively, are described. Proteins b and c of E. coli K12 were found to be associated with peptidoglycan. Protein bands, corresponding with flagellin and pilin respectively, were identified.
Mol Gen Genet 1976 Sep 23
PMID:Influence of cultural conditions and mutations on the composition of the outer membrane proteins of Escherichia coli. 78 62

Mutants of Escherichia coli K12, deficient in up to three major outer membrane proteins b, c and d have been constructed. Mutants that lack the lipopolysaccharide sugar heptose are deficient in protein b. All heptose-deficient strains are supersensitive to lysozyme, various antibiotics and detergents. They excrete the periplasmic enzyme ribonuclease I. Mutants deficient in proteins c and/or d have the same sensitivity towards these compounds as the parent strain. Cells of single, double and triple mutants are all rod-shaped. Electrophoretic analysis of cell envelope proteins indicates that in some mutants the protein deficiency is partially compensated for by increased amounts of one or two of the other major outer membrane proteins. Heptose-deficient strains have an increased amount of 2-keto-3-deoxyoctonate.
Mol Gen Genet 1976 Sep 23
PMID:Heptose-deficient mutants of Escherichia coli K12 deficient in up to three major outer membrane proteins. 78 63


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