Part of the ABC transporter complex GluABCD involved in glutamate uptake. Probably responsible for the translocation of the substrate across the membrane. The complex is composed of two ATP-binding proteins (GluA), two transmembrane proteins (GluC and GluD) and a solute-binding protein (GluB). Deletion of the gluABCD cluster almost abolishes glutamate uptake activity. Belongs to the binding-protein-dependent transport system permease family. HisMQ subfamily.