Part of the ABC transporter complex ThiBPQ involved in thiamine import (PubMed:12175925). Probably responsible for the translocation of the substrate across the membrane (Probable). Transport is inhibited by the sulfhydryl-specific modifier N-ethylmaleimide. The complex is composed of two ATP-binding proteins (ThiQ), two transmembrane proteins (ThiP) and a solute-binding protein (ThiB). Belongs to the binding-protein-dependent transport system permease family. CysTW subfamily.