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Biomedical subjects

J R Roth

Publications and source records attributed to J R Roth.

At least 127 records · Page 7Linked to original sources
PubMed1976

Yeast suppressors of UAA and UAG nonsense codons work efficiently in vitro via tRNA.

A cell-free protein-synthesizing system, containing an S-100 fraction from yeast, ribosomal subunits from Krebs ascites cells, and ribosome initiation factors from rabbit reticulocytes, translates yeast, adenovirus, and rabbit globin messenger RNAs and the RNA from bacteriophage Qbeta. An amber mutation in the Qbeta synthetase gene is suppressed in vitro if the S-100 fraction s from yeast strains carrying amber suppressor mutations. Suppressor SUP6-2 gives 16% suppression, and the recessive lethal suppressor RL-1 gives 50% suppression. Extracts from strain FM6, which has the ochre suppressor SUP4-1, give a longer protein product from the normal synthetase gene at Qbeta with an efficiency of 63%. This implies that UAA is the terminator for the synthetase gene, and that synthesis of this read through protein can be used as an assay for ochre suppression. Suppression in each of these cases is mediated by tRNA, since pufified tRNA is the only fraction from suppressing strains that is required in an otherwise nonsuppressing cell-free system.

Bacteriophages↗
PubMed1975

Regulation of histidine operon does not require hisG enzyme.

Mutations are described which delete all or part of the first structural gene (hisG) of the histidine operon of Salmonella typhimurium. Physiological regulation of histidine enzymes occurs normally in strains carrying any deletion that has both endpoints within the hisG gene. Constitutive high operon expression is observed in strains carrying any hisG deletion and an unlinked regulatory mutation, hisT1504. These results strongly indicate that the hisG protein is not an essential component of the mechanism for regulating expression of the histidine operon.

Cell Division↗
PubMed1975

Transfer ribonucleic acid methylase deficiency found in UGA supressor strains.

Extracts of recessive UGA suppressor strains, designated supK, are deficient in transfer ribonucleic acid (tRNA)-methylating activity when compared to wild-type extracts. Moreover, the tRNA from suppressor strains is methyl deficient when compared to wild-type tRNA. This deficiency is due to the lack of a single tRNA methylase activity in suppressor strains. UGA suppressor activity may be caused by the miscoding of one or more methyl-deficient tRNA's in supK strains.

Cell-Free System↗
PubMed1971

Histidine regulation in Salmonella typhimurium. 8. Mutations of the hisT gene.

The hisT gene, one of six genes in which mutation causes derepression of the histidine operon in Salmonella typhimurium, is shown to code for a protein that is not essential for the growth of the bacteria. This is indicated by the characterization of particular classes of mutations in the hisT gene: amber mutations, frame-shift mutations, and temperature-sensitive mutations that affect repression but not growth. In addition, the class of semilethal mutations was selected for but not found.

Alanine↗