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Biomedical subjects

B H Sells

Publications and source records attributed to B H Sells.

At least 91 records · Page 5Linked to original sources
PubMed1970

Polysome stability in relaxed and stringent strain of Escherichia coli during amino acid starvation.

The influence of amino acid starvation on polysome content was examined in relaxed and stringent strains of Escherichia coli which were isogenic for the RC locus. No difference was observed between the polysome profiles obtained from two different sets of stringent and relaxed strains starved for the same amino acid. In both relaxed and stringent strains, starvation for amino acids other than methionine resulted in only a slight breakdown of polysomes with a concomitant increase of 70S ribosomes. However, starvation for methionine in both RC stringent and relaxed strains of E. coli resulted in a more extensive degradation of polysomes and accumulation of 70S ribosomes. The 70S ribosomes obtained as a result of methionine starvation were more sensitive to degradation to 50 and 30S subunits in 10(-3)m Mg(2+) than 70S monomers obtained either by degradation of polysomes with ribonuclease or by starvation of cells for amino acids other than methionine. The 70S ribosomes from methionine starvation were similar (sensitivity to 10(-3)m Mg(2+)) to 70S ribosomes obtained from cells in which initiation of protein synthesis had been prevented by trimethoprim, an inhibitor of formylation. Since N-formyl-methionyl-transfer ribonucleic acid is required for initiation, the 70S ribosomes obtained in both methionine-starved and trimethoprim-treated cells must result from association of 50 and 30S subunits for reasons other than reinitiation. These results suggest that the level of ribonucleic acid synthesis does not influence the distribution of ribosomes in the polysome profile and vice versa.

Amino Acids↗
PubMed1968

Ribosome biogenesis: nonrandom addition of structural proteins to 50S subunits.

Assemblage of structural proteins into 50S subunits was examined in Escherichia coli recovering fromt chloramphenicol treatment. Cells previously labeled with H3-leucine for three generations were incuibated for 30 minutes with chloramnlphenicol. Proteins synthesized during the initial 5 minuites of recovery from chlorarmphenicol treatmnent were labeled with C(14)-leucine. Marked variation in the ratios of C(14)- to H(3)-leucine in ribosomal protein occurred in cells that had been treated with chloramphenicol; luntreated cells displayed little variation. Thle resuilts sliggest that ribosomal proteins are assenmbled into 50S subunits in a nonrandom manner.

Bacterial Proteins↗