Immature 50 S subunits in Escherichia coli polyribosomes.
Explore the source record for details and available documents.
Escherichia coli↗
Biomedical subjects
L Silengo
Publications and source records attributed to L Silengo.
Mutagenicity of diallate, sulfallate, and triallate and relationship between structure and mutagenic effects of carbamates used widely in agriculture.
In an investigation of the mutagenic properties of 20 carbamate herbicides and fungicides by use of the Salmonella/microsome mutagenicity test as developed by Ames et al. (Mutation Res., 31: 347-364, 1975), we have found that three thiocarbamate compounds, diallate, sulfallate and triallate, are mutagenic in the presence of a liver microsomal fraction on strains TA1535 and TA100. This indicates that the metabolic products of these thiocarbamates are causing base-pair substitutions. Since the 2-chloro-allyl group is common to the three mutagenic compounds but is not common to the 17 nonmutagenic compounds, a metabolic derivative of this group is probably responsible for the mutagenic activity.
Animals↗
Mutagenicity of pesticides containing 1,3-dichloropropene.
In a systematic study of the mutagenic effect of chemical compounds used as pesticides, we found that D. D. soil fumigant and Telone are mutagenic. The test was performed using the bacterial tester strains following the procedure developed by Ames. The active principle of D. D. soil fumigant and Telone is a mixture of the cis and trans isomers of 1,3-dichloropropene. Both isomers are mutagenic in Salmonella strains TA 1535 and TA 100. 2,3-Dichloro-1-propene, a minor component (5%) of the commercial preparation Telone, was also found to be mutagenic in strains TA 1535 and TA 100. Mutagenesis of these tester strains is an indication of a base-pair substitution event causing a missense mutation. 1,3-Dichloropropene is widely used in agriculture all over the world. In Italy 2,187,100 kg were produced in 1972. In California over 1,000,000 kg of 1,3-dichloropropene-containing pesticides were used in 1971.
Allyl Compounds↗
Stability of "spacer" sequences of pre-ribosomal RNA in Escherichia coli.
"SPACER" SEQUENCES OF AN RRNA gene transcript were detected with high efficiency by hybridization with DNA of the specilized transducing phase phi80rrn. Hybridization-competition studies revealed that 20 to 23% of the 30S precursor rRNA, obtained from E. coli mutant strain AB301/105, consist of "spacer" sequences. The "spacer" sequences formed hybrids with E. coli DNA, but not with Vibrio DNA. Experiments with RNA labeling in the presence of rifampicin showed that more than 80% of the spacer sequences arrive in full-length 30S pre rRNA chains before any cleavage of the RNA occurs. The hybridization assays also permitted the detection of "spacer" sequences in pulse-labeled rRNA of wild-type cells, in which the 30S pre-rRNA is already cleaved during its synthesis. Many of these "spacer" sequences degraded to alcohol-soluble materials with a half-life time of 1.2 min. The half-life was not lengthened by the treatment of cells with chloramphenicol, which stabilizes bulk mRNA. However, unstable "spacer" sequences transcribed in cells deficient in RNase III exhibited slower degradation, with a half-life time of about 9 min, whereas the cleavage of 30S pre-rRNA to smaller RNA species occurred with a half-life of about 3 min. These results are consistent with the notion that a rate-limiting action of RNase III in the initial attack leads to degradation of "spacer" sequences in rRNA gene transcript; and that degradation is not at all connected with ribosome translocation.
Base Sequence↗
Ribosome maturation in E. coli.
In vivo and in vitro experiments have shown that processing of ribosomal RNA is a late event in ribosome biogenesis. The precursor form of RNA is probably necessary to speed up the assembly of ribomal proteins. Newly formed ribosomal particles which have already entered polyribosomes differ from mature ribosomes not only in their RNA content but also in their susceptibility to unfolding in low Mg concentration and to RNase attack. Final maturation of new ribosomes is probably dependent on their functioning in protein synthesis. Thus only those ribosomes which have proven to be functional may be converted into stable cellular structures.
Escherichia coli↗