Probably involved in tryptophan uptake. Its translation is regulated by tryptophan-activated RNA-binding regulatory protein (TRAP). Cells lacking this gene grow on 40-fold higher concentrations of the tryptophan analog 5-fluorotryptophan than the level that inhibits the wild-type strain. Belongs to the vitamin uptake transporter (VUT/ECF) (TC 2.A.88) family. TrpP subfamily.