Satoshi Dekio

Biochemical and genetic studies on two different types of erythromycin resistant mutants of Escherichia coli with altered ribosomal proteins

SummaryRibosomes from nine E. coli mutants with high level resistance to the antibiotic erythromycin were isolated and their proteins were compared with those of the parental strains by two-dimensional polyacrylamide gel electrophoresis, by carboxymethylcellulose column chromatography and by immunological techniques. Two 50S proteins were found to be altered in the mutants: either L 4 or L 22.Ribosomes with an altered L4 protein bound erythromycin rather poorly and the formation of N-acetylphenylalanyl puromycin was drastically decreased. On the other handribosomes with an altered L22 protein bound erythromycin as efficiently as wild type ribosomes and their puromycin reaction was at least as good as that of wild type ribosomes.Transduction experiments showed that the mutations affecting both proteins, L4 and L22, are located very close to the str and spc genes, nearer to the spc than to str gene.

INCREASE OF ACIDIC NUCLEAR PROTEINS AND DNA SYNTHESIS IN HUMAN LYMPHOCYTES ACTIVATED BY PHYTOHEMAGGLUTININ

Acidic nuclear proteins and histones were extracted at several points in time from human lymphocytes cultured in media containing phytohemagglutinin, and their amounts were measured according to Folin‐Lowrys technique. The amount of acidic nuclear proteins continually increased, but the histone level neither increased nor decreased. It is suggested that acidic nuclear proteins might restore histone‐inhibited DNA‐dependent RNA synthesis in human lymphocytes activated by phytohemagglutinin.

LOW LEVEL OF ACIDIC NUCLEAR PROTEINS IN RAT FIBROBLASTS CULTURED IN MEDIUM CONTAINING PREDNISOLONE

The growth rate of rat fibroblasts cultured in medium containing prednisolone was lower than that of those cultured in medium not containing prednisolone. Acidic nuclear proteins and histones were extracted from the nuclei of cultured rat fibroblasts. The amounts of the extracted nuclear proteins were measured with Folin‐Lowrys technique, and the ratios of acidic nuclear proteins to histones were calculated. The ratio of nuclear proteins from rat fibroblasts cultured in medium containing prednisolone was lower than that of those cultured in medium not containing prednisolone. It is suggested that the low level of acidic nuclear proteins in medium containing prednisolone may cause repressed protein synthesis and thus growth inhibition in cultured fibroblasts.