Part of the ABC transporter complex MglABC involved in galactose/methyl galactoside import. Responsible for energy coupling to the transport system (Probable). ATP + D-galactose(out) + H2O = ADP + D-galactose(in) + H(+) + phosphate The complex is composed of two ATP-binding proteins (MglA), two transmembrane proteins (MglC) and a solute-binding protein (MglB). Belongs to the ABC transporter superfamily. Galactose/methyl galactoside importer (TC 3.A.1.2.3) family.