Part of the ABC transporter complex OpuCABCD involved in carnitine uptake. Probably responsible for energy coupling to the transport system. Involved, with BetL and GbuABC, in osmoprotection and cryoprotection of Listeria. Can also mediate weak glycine betaine transport. ATP + H2O + quaternary ammonium(out) = ADP + H(+) + phosphate + quaternary ammonium(in) The complex is composed of two ATP-binding proteins (OpuCA), two transmembrane proteins (OpuCB and OpuCD) and a solute-binding protein (OpuCC). The complex is induced by either hyperosmotic stress or by low temperature. Osmotic induction is sigma B-dependent. Belongs to the ABC transporter superfamily.