Part of the ABC transporter complex ThiBPQ involved in thiamine import (PubMed:9535878). Probably responsible for the translocation of the substrate across the membrane (Probable). Is also involved in thiamine pyrophosphate transport (PubMed:9535878). The complex is composed of two ATP-binding proteins (ThiQ), two transmembrane proteins (ThiP) and a solute-binding protein (ThiB). Expression is repressed by thiamine. Insertions in thiBPQ cause a defect in the transport of both thiamine and TPP. Belongs to the binding-protein-dependent transport system permease family.