Probable ATP-binding component of the energy-coupling factor (ECF) transporter complex LarMNQO involved in nickel import. LarO is presumably responsible for energy coupling to the transport system. May form an energy-coupling factor (ECF) transporter complex composed of an ATP-binding protein (A component, LarO), a transmembrane protein (T component, LarQ) and a fused possible substrate-capture protein (S component, LarMN) of unknown stoichiometry. Induced by L-lactate but not by a racemic mixture of DL-lactate. Makes part of the larR(MN)QO operon. Deletion of both larO and larQ leads to a loss of lactate racemase activity. Addition of Ni(2+) (but not Co(2+)) restores lactate racemase activity in this mutant. Belongs to the ABC transporter superfamily.