Synthesis in vivo of polynucleotide phosphorylase in escherichia coli: I. Effect of amino acids on polynucleotide phosphorylase activity in a chloramphenicol-inhibited system

Abstract

A method has been developed for the rapid estimation of polynucleotide phosphorylase (nucleosidediphosphate: polynucleotide nucleotidyltransferase, EC 2.7.7.8) activity in toluene-treated suspensions of bacteria. The assay has been used to follow the production of the enzyme in a tryptophan auxotroph of Escherichia coli in the presence or absence of chloramphenicol. Both the level of polynucleotide phosphorylase activity and the RNA content of bacteria treated with this antibiotic are increased two-fold relative to the amounts synthesized in its absence, although the total protein content of the cells rises by less than 5%. The effect is tryptophan-dependent and both increments are proportional to the concentration of this amino acid. Similar increases are observed when tryptophan is replaced by 5-methyl-tryptophan, even though this compound does not support growth.