Transmembrane (T) component of an 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. Expression of the complex plus RibU in de-energized E.coli allows riboflavin uptake. Forms a stable energy-coupling factor (ECF) transporter complex composed of 2 membrane-embedded substrate-binding proteins (S component), 2 ATP-binding proteins (A component) and 2 transmembrane proteins (T component) upon coexpression of the components in E.coli. May be able to interact with more than 1 S component at a time. Belongs to the energy-coupling factor EcfT family.