Essential for high-level bacitracin resistance (PubMed:15388429). Part of the ABC transporter complex BcrAB. Probably responsible for energy coupling to the transport system (Probable). The complex is probably composed of two ATP-binding proteins (BcrA) and two transmembrane proteins (BcrB). Transcription is activated by the regulatory protein BcrR in the presence of bacitracin. Disruption mutant is sensitive to bacitracin. Belongs to the ABC transporter superfamily.