Search PubMed⌕ Search

Biomedical subjects

S Schlesinger

Publications and source records attributed to S Schlesinger.

123 records · Page 7Linked to original sources
PubMed1969

Mutants of Escherichia coli with an altered tyrosyl-transfer ribonucleic acid synthetase.

We have isolated several mutants defective in the gene for tyrosyl-transfer ribonucleic acid (tRNA) synthetase (tyrS). One of these mutants is described in detail. It was isolated as a tyrosine auxotroph with defects both in the tyrosyl-tRNA synthetase and in the tyrosine biosynthetic enzyme, prephenate dehydrogenase. It also had derepressed levels of the tyrosine-specific 3-deoxy-d-arabinoheptulosonic acid-7-phosphate (DAHP) synthetase. The latter finding suggested that a wild-type tyrS gene was required for repression of the tyrosine biosynthetic enzymes. The following results demonstrated that this hypothesis was not correct. (i) When the defective tyrS gene was transferred to another strain, the tyrosine-specific DAHP synthetase in that strain was not derepressed, and (ii) two other mutants with defective tyrosyl-tRNA synthetases had repressed levels of the tyrosine biosynthetic enzymes. The tyrS gene was located near minute 32 on the Escherichia coli chromosome by interrupted mating experiments.

Amino Acids↗
PubMed1967

Submaxillary gland of mouse: properties of a purified protein affecting muscle tissue in vitro.

A protein from the salivary gland of mice has been highly purified. It affects embryonic muscle tissue in vitro and has both esterase and peptidase activities. Addition of the pure protein to tissue culture in synthetic medium causes dissociation of muscle fibers in individual myoblasts with loss of myosin. This biological activity, as well as the esterase activity, is inhibited by low concentrations of phenylmethanesulfonyl fluoride; this suggests that the effect on the tissue is a consequence of the protein's enzymatic activities.

Animals↗
PubMed1967

Inhibition of growth of Escherichia coli and of homoserine O-transsuccinylase by alpha-methylmethionine.

The methionine analogue, alpha-methylmethionine, inhibits bacterial growth, but its action is overcome by methionine, homocysteine, and cystathionine. The effect of the analogue on growth is attributed to its ability to mimic methionine as a feed-back inhibitor of the first enzyme specific to methionine biosynthesis. This conclusion is based on the findings that (i) alpha-methylmethionine inhibits excretion of O-succinylhomoserine, the product of the first enzyme, by a methionine auxotroph unable to convert succinylhomoserine to cystahionine, and that (ii) the enzyme homoserine O-transsuccinylase is inhibited by alpha-methylmethionine in extracts of Escherichia coli. alpha-Methylmethionine also inhibits methionyl-ribonucleic acid synthetase in extracts, but this inhibition probably does not affect growth.

Amino Acids↗