Figure 1.

Known genes of tryptophan metabolism in E. coli. The five operons previously shown to be down-regulated by the trp repressor are marked by arrows leading from trpR, the structural gene for the trp repressor. In the present study, aroF-tyrA, aroG, and aroP also were down-regulated by tryptophan. These three operons are regulated by TyrR, which can be activated by tryptophan. These genes and the genes of the trp repressor regulon, are shown in green. Genes of the tna operon that are up-regulated by tryptophan are shown in red. Genes encoding other enzymes of the common chorismate pathway are not shown.