title: Involvement of the L-cysteine biosynthetic pathway in azide-induced mutagenesis in Salmonella typhimurium.
abstract: L-Cystine and L-cysteine specifically reverse the mutagenic action of azide in Salmonella typhimurium and Escherichia coli. To establish whether the L-cysteine biosynthetic pathway is involved in azide-induced mutagenesis, several derivatives of a mutagen tester-strain of S. typhimurium bearing mutations in different cys genes were isolated. No mutagenic effect of azide was observed in a strain carrying mutation in the cysE gene, unless the incubation medium was supplemented with exogenous O-acetylserine. Our of 16 cysK mutants 14 were mutagenized by azide very poorly or not at all. These results indicate that the activity of O-acetylserine sulfhydrylase A, and the availability of O-acetylserine, one of the two co-substrates of the enzyme, are essential for the mutagenic action of azide in S. typhimurium.
mesh_terms: D001386:Azides / Q000494:pharmacology*; D003545:Cysteine / Q000235:genetics*; D004352:Drug Resistance, Microbial; D005796:Genes; D009153:Mutagens / Q000378:metabolism*; D009154:Mutation; D012486:Salmonella typhimurium / Q000235:genetics*; D014161:Transduction, Genetic
chemical_list: D001386:Azides; D009153:Mutagens; D003545:Cysteine