Involved in the efflux of sugars. The physiological role may be the reduction of the intracellular concentration of toxic sugars or sugar metabolites. Transports IPTG, lactose and melibiose. Activated by glucose, and to a lesser extent by other metabolizable sugars such as galacturonate, arabinose and melibiose. Repressed by cyclic AMP receptor protein (CRP). Belongs to the major facilitator superfamily. SotB (TC 2.A.1.2) family.