Responsible for transport of beta-galactosides into the cell, with the concomitant uptake of protons (symport system), and also for transport of homologous and heterologous exchange of beta-galactosides. By lactose. The PTS EIIA type-1 domain may serve a regulatory function, through its phosphorylation activity. In the N-terminal section; belongs to the sodium:galactoside symporter (TC 2.A.2) family.