Part of the ABC transporter complex YtrBCDEF that plays a role in acetoin utilization during stationary phase and sporulation. The complex is composed of 2 ATP-binding proteins (YtrB and YtrE), 2 transmembrane proteins (YtrC and YtrD) and a solute-binding protein (YtrF). Expressed early in the stationary phase. Negatively regulated by YtrA. Belongs to the ABC transporter superfamily.