title: Escherichia coli and Salmonella typhimurium supX genes specify deoxyribonucleic acid topoisomerase I.
abstract: Mutations of the Escherichia coli or Salmonella typhimurium supX genes eliminated deoxyribonucleic acid topoisomerase I. Suppression of a supX amber mutation partially restored the topoisomerase. Multicopy plasmids carrying supX+ caused overproduction of topoisomerase. Thus, these supX genes were identified as topA genes which specify deoxyribonucleic acid topoisomerase I.
mesh_terms: D004264:DNA Topoisomerases, Type I / Q000096:biosynthesis / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics*; D005796:Genes; D009154:Mutation; D010957:Plasmids; D012486:Salmonella typhimurium / Q000235:genetics*; D013489:Suppression, Genetic
chemical_list: D004264:DNA Topoisomerases, Type I