Probably a biotin-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. In E.coli forms a stable energy-coupling factor (ECF) transporter complex composed of 2 membrane-embedded substrate-binding protein (S component), 2 ATP-binding proteins (A and A' components) and 2 transmembrane proteins (T component), probably with a stoichiometry of 2:1:1:2. May be able to interact with more than 1 S component at a time. Belongs to the BioY family.