Search PubMed⌕ Search

Biomedical subjects

G H Jones

Publications and source records attributed to G H Jones.

At least 145 records · Page 8Linked to original sources
PubMed1979

Effects of ribosomal wash factors and spermidine on endogenous and exogenous mRNA stimulated protein synthesis in the wheat germ cell-free system.

Differential effects of Mg2+, spermidine, and reticulocyte ribosomal wash factors on the translation of endogenous, myeloma, and globin mRNA's have been observed in studies with the wheat germ cell-free protein synthesizing system. Spermidine stimulated globin mRNA translation but not the translation of endogenous wheat germ messages, and the polyamine actually inhibited the translation of myeloma mRNA. Ribosomal wash factors, on the other hand, stimulated endogenous and myeloma mRNA dependent protein synthesis in an Mg2+-dependent fashion but inhibited globin mRNA translation. The combination of ribosomal wash factors and spermidine was either stimulatory or inhibitory depending on the Mg2+ concentration and the message. It was further observed that translation of exogenous myeloma mRNA proceeded for only 60 min at 25 degrees C under all conditions tested in this study, while translation of endogenous wheat germ messages continued for longer periods of time. No differential effects of spermidine on the synthesis of high molecular weight myeloma proteins were observed.

Animals↗
PubMed1977

Relationship between changes in the translational apparatus and actinomycin production in Streptomyces antibioticus.

As previously reported (G. H. Jones, 1975), transfer ribonucleic acids (tRNA's) and ribosomes from actinomycin-producing cultures of Streptomyces antibioticus show a decreased ability to function in aminoacylation and translation as compared with the corresponding components from younger cells. Further, specific changes in the isoacceptor patterns are revealed when tRNA's from actinomycin-producing cells are compared with those of younger cells by reverse- phase column chromatography. A specific glycyl-tRNA species is eliminated from the reverse-phase profile of tRNA's from actinomycin-producing S. antibioticus cells as compared with younger cells. Changes in isoacceptor patterns were also observed for the amino acids methionine, valine, phenylalanine, and leucine. Actinomycin synthesis was inhibited by growing S. antibioticus cells in the presence of alpha-methyl-DL-tryptophan. Inhibition of actinomycin synthesis reversed the changes in tRNA observed in normally grown control cultures, although it had no demonstrable effect on the growth of the cells. Thus, tRNA from 48-h-old, alpha-methyl-tryptophan-grown cells had amino acid acceptor activity that was equal to or greater than that of tRNA from 12-h-old, normally grown cells. Similarly, the reverse-phase chromatographic pattern for glycyl-tRNA's from 48-h-old, alpha-methyl-tryptophan-grown cells was identical to that of the glycyl-tRNA's from 12-h-old, normally grown cells. In contrast, the ability of ribosomes from 48-h-old, alpha-methyl-tryptophan-grown cells to function in polypeptide synthesis in vitro was essentially identical to that of 48-h-old, normally grown cells. Ribosomes from 12-h-old, normally grown cells were severalfold more active in in vitro polypeptide synthesis.

Bacterial Proteins↗
PubMed1976

RNA synthesis in Streptomyces antibioticus: in vitro effects of actinomycin and transcriptional inhibitors from 48-h cells.

Two forms of DNA-dependent RNA polymerase have been partially purified (about 100-fold relative to the crude extract) from 48-h old cells of Streptomyces antibioticus. The two forms show different Mg2+ optima for the incorporation of [3H]UMP into RNA. Substances inhibiting transcription have been isolated by ammonium sulfate precipitation from one of the fractions produced during the polymerase purification. Actinomycin can be shown to inhibit RNA synthesis catalyzed by the S. antibioticus polymerases to a similar extent regardless of the template used. When S. antibioticus DNA is the template, actinomycin inhibits transcription by S. antibioticus polymerase to a degree that is significantly less than the observed actinomycin inhibition of synthesis catalyzed by Escherichia coli polymerase or by either S. antibioticus or E. coli polymerase with calf thymus DNA as the template. Using an assay previously developed, it was shown that the association constant for the binding of actinomycin to S. antibioticus DNA was increased by the presence of RNA polymerase in the binding mixture, while the association constant for the binding to calf thymus DNA was decreased by RNA polymerase. RNA synthesis in crude, cell-free extracts of 12-h old S. antibioticus cells (not producing actinomycin) is less refractory to actinomycin inhibition than synthesis catalyzed by extracts of 48-h old (actinomycin producing) cells, and both extracts catalyze appreciable RNA synthesis at actinomycin concentrations that completely inhibit RNA synthesis catalyzed by E. coli extracts.

Bacterial Proteins↗