Part of the ABC transporter complex ThiBPQ involved in thiamine import (PubMed:9535878). 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 bacterial solute-binding protein 1 family.