Location of the gene for the low-affinity tryptophan-specific permease of Escherichia coli.

L-Tryptophan uptake was assayed under conditions in which the aroT gene had been inactivated by deletion and the product of the aroP permease was competitively inhibition. A mutant carrying a deletion from bgl through tnaA showed negligible L-tryptophan uptake, in contrast to a strain possessing an intact tna region or to strains carrying point mutations in tna. The ability to take up L-tryptophan was not restored by lysogenizing the tna-deleted strain with lambda tna+.