Part of the OsmU ABC transporter complex, which is involved in the uptake of osmoprotectants such as choline-O-sulfate and glycine betaine. Probably responsible for energy coupling to the transport system. The complex is composed of two ATP-binding proteins (OsmV), two transmembrane proteins (OsmW and OsmY) and a solute-binding protein (OsmX). Induced by osmotic stress. Part of the osmU operon, which consists of four genes (osmV, osmW, osmX and osmY). Deletion of the osmU operon eliminates the residual osmoprotection by glycine betaine in a mutant that is lacking the ProP and the ProU systems. OsmU deletion has no effect on the utilization of glycine betaine as an osmoprotectant when ProP or ProU are functional. Belongs to the ABC transporter superfamily.