Histidine Regulation in Salmonella typhimurium XV. Procedure for the Selection of Mutants Unable to Derepress the Histidine Operon

A general search has been made for mutants defective in their ability to derepress the histidine operon. The procedure was to select for mutants with an increased sensitivity to the false feedback inhibitor, 2-thiazolealanine. Five mutant strains defective in derepression have been isolated. All five strains are unable to derepress normally because of mutations located in the operator-promoter region of the histidine operon.