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Biomedical subjects

D G Wild

Publications and source records attributed to D G Wild.

At least 37 records · Page 2Linked to original sources
PubMed1976

Peptidyltransferase activity of ribosomes and a ribosome precursor from a mutant of Escherichia coli.

Escherichia coli strain 15-28 is a mutant with a defect in ribosome synthesis that caused the accumulation of ribonucleoprotein ('47S') particles during exponential growth. These particles are precursors to 50S ribosomes that lack three ribosomal proteins. Peptidyltransferase activity and binding at the peptidyl site of the peptidyltransferase centre are greatly decreased in 47S particles. Both these activities are lower in the 50S and 70S ribosomes of strain 15-28 than in its parent. Unusual assembly of the larger ribosomal subunit in strain 15-28 may produce completed ribosomes with diminished biological activity.

Acyltransferases↗
PubMed1976

The composition of an unusual precursor of 50 S ribosomes in a mutant of Escherichia coli.

Escherichia coli strain 15--28 is a mutant which during exponential growth contains large amounts of a '47S' ribonucleoprotein precursor to 50S ribosomes. The '47S particles' are more sensitive to ribonuclease than are 50S ribosomes. The 23 S RNA of 47S particles may be slightly undermethylated, but cannot be distinguished from the 23S RNA of 50S ribosomes by sedimentation or electrophoresis. Isolated particles have 10--15% less protein than do 50S ribosomes; proteins L16, L28 and L33 are absent. Comparison with precursor particles studied by other workers in wild-type strains of E. coli suggests that the assembly of 50S ribosomes in strain 15--28 is atypical.

Bacterial Proteins↗
PubMed1976

An unusual precursor of 50S ribosomes in a mutant of Escherichia coli.

Escherichia coli strain 15-28 is a mutant with a defect in ribosome synthesis that leads to the accumulation of large amounts of ribonucleoprotein ("47S") particles during exponential growth. These particles are precursors to 50S ribosomes, but are distinct from precursors detected by pulse-labelling of the parent strain and also from ribosome precursors that accumulate during inhibition of growth by CoC12. Either ribosome assembly in the mutant differs from that in the wild-type strain, or 47S particles represent a hitherto unstudied stage in the synthesis of 50S ribosomes.

Centrifugation, Isopycnic↗
PubMed1975

A 30 S precursor of 30 S ribosomes in a mutant of Escherichia coli.

Escherichia coli 15-28, a mutant with a defect in ribosome metabolism, accumulates a ribonucleoprotein particle that is indistinguishable from 30S subunits by sedimentation but contains the precursor form of 16S RNA. This particle is probably a precursor of 30 S ribosomes.

Centrifugation, Density Gradient↗
PubMed1973

Regulation of uptake of purines, pyrimidines and amino acids by Candida utilis.

Uptake of uracil by Candida utilis is increased by addition of leucine to a minimal medium in which organisms are growing. This response requires protein synthesis and has kinetics consistent with the induction of additional uracil transport by the amino acid or a derivative. Consequently, the contribution of exogenous radioactive uracil to the pyrimidine nucleotide pools increases so that RNA made after the amino acid is added is of greater specific radioactivity. Some other amino acids are as effective as leucine in increasing the incorporation of uracil into RNA. Growth with leucine present also increases to different extents the initial rates of uptake of adenine, cytosine, uridine, lysine, histidine, threonine, phenylalanine, aspartic acid and leucine itself. The action of leucine on lysine transport appears to involve induction. These effects are not restricted to leucine; growth with aspartic acid or phenylalanine in the medium gives similar results. Lysine, on the other hand, is without action on the uptake of leucine, aspartic acid, phenylalanine, threonine or uracil but decreases the initial rates of uptake of both histidine and lysine. We suggest that lysine represses its own transport. Similarly, there is a specific decrease in uracil uptake caused by growth with this pyrimidine. Thus in C. utilis there are complex interrelationships in the uptake of nitrogen-containing compounds.

Journal Article↗
PubMed1973

Ribosome precursors accumulated by Escherichia coli during incubation with cobalt chloride.

The ribonucleoprotein particles that accumulate during inhibition of Escherichia coli by CoCl(2) are ribosome precursors. The RNA that they contain can be transferred intact to completed ribosomes. The particles contain less protein than do ribosomes, but this protein appears identical with proteins from the appropriate ribosomal subunit. At least one of the particles is heterogeneous.

Bacterial Proteins↗
PubMed1971

Altered ribosomes after inhibition of Escherichia coli by rifampicin.

Addition of rifampicin to growing cells of Escherichia coli affected the ribosomes. The polyribosomes first decayed to 70S ribosomes. These later dissociated to particles distinct from ribosomal subunits. The altered ribosomes sedimented more slowly than the corresponding subunits and had lost some protein; their ribosomal RNA was intact, but they were more susceptible to degradation by ribonuclease than normal ribosomes. The addition of rifampicin to preparations of lysed cells caused no detectable changes in the ribosome fraction.

Carbon Isotopes↗
PubMed1969

Inhibition of bacterial growth by metal salts. A survey of effects on the synthesis of ribonucleic acid and protein.

Inhibition of the growth of Escherichia coli M.R.E. 600 by six different metal salts was accompanied by a greater decrease in the synthesis of RNA than in that of protein. The action of cobalt chloride was exceptional; inhibited cells made an excess of RNA to an extent depending on the concentration of Co(2+), the time of incubation and the concentration of Mg(2+) in the medium. Preferential synthesis of RNA in the presence of cobalt chloride was not confined to E. coli but occurred to various extents in some, but not all, of the other micro-organisms that were tested. Possible reasons for the special effect of Co(2+) are discussed.

Bacteria↗