Thiamine-binding protein that interacts with the energy-coupling factor (ECF) ABC-transporter complex. Unlike classic ABC transporters this ECF transporter provides the energy necessary to transport a number of different substrates. The substrates themselves are bound by transmembrane, not extracytoplasmic soluble proteins and transport it into cells. Binds thiamine with a dissociation constant of 0.5 nM. Upon coexpression with its energy-coupling factor (ECF) ABC-transporter complex EcfA1A2T in Lactococcus lactis subsp. cremoris (strain NZ9000) allows thiamine uptake; uptake requires both ThiT and EcfA1A2T. In Lactococcus lactis subsp. cremoris (strain NZ9000) forms a stable energy-coupling factor (ECF) transporter complex probably composed of a membrane-embedded substrate-binding protein (S component), two ATP-binding proteins (A components) and a transmembrane protein (T component). Belongs to the vitamin uptake transporter (VUT/ECF) (TC 2.A.88) family. Thiamine transporter subfamily.