title: Roles of the relA(+) gene and of 4-thiouridine in near-ultraviolet (344 nm) radiation inhibition of induced synthesis of tryptophanase in Escherichia coli B/r.
abstract: Near-ultraviolet radiation (near UV; 300-380 nm) is known to inhibit the induced synthesis of tryptophanase by tryptophan in Escherichia coli, showing an action spectrum similar to that for near-UV-induced growth delay. The present work shows that a relA mutant of E. coli B/r exhibits 50% as much monochromatic near-UV (334 nm) inhibition of tryptophanase induction as the wild type, and tht a mutant lacking 4-thiouridine, an unusual nucleoside in tRNA, exhibits greater than 10% as much inhibition of tryptophanase induction. These findings indicate that 4-thiouridine is almost the sole chromophore for this effect in E. coli B/r, but that only 50% of the effect operates by a mechanism utilizing the relA(+) gene product; growth delay appears not to be primarily involved.
mesh_terms: D004790:Enzyme Induction / Q000528:radiation effects; D004926:Escherichia coli / Q000235:genetics / Q000528:radiation effects*; D005798:Genes, Bacterial / Q000528:radiation effects*; D008190:Lyases / Q000096:biosynthesis*; D013891:Thiouridine / Q000235:genetics*; D014368:Tryptophanase / Q000096:biosynthesis*
chemical_list: D013891:Thiouridine; D008190:Lyases; D014368:Tryptophanase