The phosphoenolpyruvate-dependent sugar phosphotransferase system (sugar PTS), a major carbohydrate active transport system, catalyzes the phosphorylation of incoming sugar substrates concomitantly with their translocation across the cell membrane. The enzyme II LacEF PTS system is involved in lactose transport. Binds 1 Mg(2+) ion per trimer. Homotrimer. Induced by lactose, galactose and galactose-6-P. Repressed by glucose. The PTS EIIA type-3 domain is phosphorylated by phospho-HPr on a histidyl residue. Then, it transfers the phosphoryl group to the PTS EIIB type-3 domain. Extended N-terminus.