Absence Of Putrescine Research Articles

Polyamine requirement for streptomycin action on protein synthesis in bacteria.

The effect of streptomycin on polypeptide synthesis in vivo and in vitro has been investigated using polyamine auxotrophic mutants of Escherichia coli grown in the presence or in the absence of putrescine. We found that streptomycin caused a marked inhibition of protein synthesis in polyamine-supplemented cells whereas bacteria starved for polyamines were less sensitive to the action of the antibiotic. Neomycin, kanamycin and kasugamycin had a behaviour similar to streptomycin while spectinomycin, gentamicin and tetracycline brought about a strong inhibition of protein synthesis both in polyamine-starved and unstarved bacteria. The increase of misreading induced by the addition of streptomycin in vivo was higher in extracts derived from bacteria cultivated in the presence of polyamines. This effect was observed in cell-free systems of streptomycin-sensitive and resistant strains. In contrast, spermidine added in vitro caused an improvement in the accuracy of translocation. Analysis of sodium dodecyl sulphate/polyacrylamide gel electrophoresis of the labelled polypeptides synthesized in vivo seems to indicate that the starvation for polyamine or the presence of streptomycin may lead to premature termination with the appearance of unfinished peptide chains.

Defect in the Split Proteins of 30‐S Ribosomal Subunits and Under‐Methylation of 16‐S Ribosomal RNA in a Polymamine‐Requiring Mutant of Escherichia coli Grown in the Absence of Polymines

Polyphenylalanine synthesis was carried out with Escherichia coli Q13 50-S ribosomal subunits and reconstituted 30-S particles containing different combinations of 23-S core particles and 30-S subunit split proteins obtained from a polyamine-requiring mutant of E. coli during its growth in the presence or absence of putrescine. It was concluded that the defect in the amount of some kinds of 30-S subunit split proteins was responsible for the decrease of polypeptide synthesis in a polyamine-requiring mutant of E. coli grown in the absence of polyamines. The methylation of 16-S RNA during growth in the absence of putrescine was decreased, while the degree of methylation of 23-S RNA did not change significantly. The decrease in methylation of 16-S RNA in the absence of putrescine was due mainly to a decrease of methylation of adenine. The relationship between the decrease of polypeptide synthetic activity of 30-S ribosomal subunits obtained from a polyamine-requiring mutant of E. coli grown in the absence of polyamines and the decrease of methylation of 16-S RNA is discussed.

Polyamine biosynthesis in human fetal liver and brain.

Extract: S-Adenosylmethionine decarboxylase specific activity in fetal (9.0–25.0 cm crown-rump length) human liver was 20-fold greater than in mature human liver, both in the absence of putrescine (63.1 ± 7.2 versus 3.5 ± 0.8 pmol CO2/mg protein/30 min) or in the presence of putrescine (116.9 ± 8.2 versus 6.2 ± 1.0 pmol CO2/mg protein/30 min). Extracts of fetal human brain did not have a significantly greater specific activity of S-adenosylmethionine decarboxylase than extracts of mature human brain when assayed in the absence of putrescine and had less when assayed in the presence of putrescine (84.7 ± 14.9 versus 175.5 ± 30.6 pmol CO2/mg protein/30 min). Ornithine decarboxylase specific activity was greater in fetal liver than in mature liver (8.8 ± 1.6 versus 1.1 ±0.3 pmol CO2/mg protein/30 min) and 20-fold greater in fetal brain than in mature brain (71.2 ± 12.1 versus 3.1 ± 1.4 pmol CO2/mg protein/30 min). The concentration of putrescine was threefold greater in fetal human liver than in mature human liver (21.6 ± 2.7 versus 6.5 ± 0.5 μmol/100 g) and eightfold greater in fetal human brain than in mature human brain (42.9 ± 2.3 versus 5.5 ± 0.6 μmol/100 g). The concentration of spermidine was fourfold greater in fetal human liver than in mature human liver (81.2 ±1.6 versus 21.4 ± 1.2 μmol/100 g), but its concentration in fetal human brain was not different from that in mature human brain. Spermine concentration was greater in fetal human liver than in mature human liver (107.3 ± 2.4 versus 70.7 ± 6.8 μmol/100 g) and greater in fetal human brain than in mature human brain (30.7 ±1.8 versus 22.1 ±0.9 μmol/100 g). Speculation: The pathway of methionine metabolism in human fetal liver and brain is adapted to conserve the sulfur of homocysteine by delayed development of the trans-sulfuration of homocysteine to cysteine. This adaptation may implement RNA synthesis, as well as protein synthesis and DNA synthesis.

Selective gene transcription in bacteriophage T4 by putrescine.

Messenger ribonucleic acid (mRNA) preparations from T4-infected cells formed in the presence or absence of putrescine have been characterized and compared. Hybrid competition experiments indicate that these mRNA molecules are derived from distinct genetic loci. The results are consistent with the hypothesis that putrescine might control differential transcription of the phage genome during morphogenesis. The data are also in accord with previously observed changes in the population of mRNA formed at different times after infection.