Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Four mutants of Escherichia coli KL16 resistant to the antibiotic Thiolutin have been isolated. This drug was earlier reported to be an inhibitor of RNA chain elongation. The first mutant, TLrI, is resistant only in rich or partially rich media: it can, however, grow in minimal medium containing the drug with a very long doubling time. The other mutants TLrII, TLrIIIa and TLrIIIb are resistant in rich as well as minimal media. beta-galactosidase could not be induced in TLrI and TLrII in the presence of thiolutin whereas the enzyme is constitutively synthesised in TLrIIIa and TLrIIIb irrespective of the drug. The mutants do not support the development of phage T4 in presence of the drug, if the drug is added along with the phage, but "escape" the inhibition if phage development is allowed to proceed for some time before the addition of the drug. The time of this escape is characteristic of the mutant. Even in a sensitive strain, T7 growth escapes inhibition very soon after infection, around the time the phage-specific RNA polymerase is synthesized. In the parent strain the kinetics of inhibition of beta-galactosidase induction resembles more the inhibition caused by rifampicin than by streptolydigin. It is proposed that thiolutin could be an inhibitor of RNA chain initiation and resistance might be due to mutation in the subunit(s)/factor(s) involved in initiation.
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PMID:Thiolutin resistant mutants of Escherichia coli are they RNA chain initiation mutants? 77 14

Thiolutin, at concentrations of 5 to 40 mug/ml, inhibited the induced synthesis of beta-galactosidase in Escherichia coli CA8000. Thiolutin had no effect on the rate of in vitro hydrolysis of o-nitrophenyl-beta-d-galactoside by purified beta-galactosidase. Examination of the effects of thiolutin on the kinetics of appearance of beta-galactosidase in the presence and absence of rifampin in induced E. coli cells indicated that thiolutin interferes with the transcription process at the level of elongation of messenger ribonucleic acid (mRNA) chains. The data indicated that, in the presence of thiolutin, beta-galactosidase mRNA has a half-life of 1.6 min and that the first completed beta-galactosidase mRNA is produced about 1.5 min after induction. These data are consistent with estimates of transcription time and messenger half-life obtained by conventional means, and suggest that thiolutin does not affect translation of mRNA or its breakdown in vivo. After removal of thiolutin, cells fully regained the ability to be induced for synthesis of beta-galactosidase within 10 min, but mRNA which was incomplete at the time of thiolutin addition did not subsequently become functional.
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PMID:Inhibition of messenger ribonucleic acid synthesis in Escherichia coli by thiolutin. 460 15