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.