Part of the ABC transporter complex GgtABCD involved in the uptake of the osmoprotective compounds glucosylglycerol (GG), sucrose and trehalose (PubMed:9006025, PubMed:11081796). Responsible for energy coupling to the transport system (Probable). The complex is composed of two ATP-binding proteins (GgtA), two transmembrane proteins (GgtC and GgtD) and a solute-binding protein (GgtB). Transcription increases in cells adapted to higher salt concentrations, whereas transcription is weak in basal medium. Insertion mutant loses its GG uptake ability, and shows leakage of glucosylglycerol from the cells into the medium. Mutation does not affect salt tolerance. Belongs to the ABC transporter superfamily.