Solute-binding protein that binds indole-3-pyruvate and indole-3-acetate (in vitro). Can also bind D-tryptophan (in vitro), but that is probably not a physiological ligand (PubMed:25540822). Probably part of a tripartite ATP-independent periplasmic (TRAP) transport system that mediates solute transport into the cytoplasm. The complex is comprised of an extracytoplasmic solute-binding protein and a heteromeric permease formed by two transmembrane proteins. Belongs to the bacterial solute-binding protein 7 family.