Part of the ProU ABC transporter complex involved in glycine betaine and proline betaine uptake. Probably responsible for energy coupling to the transport system. The complex is composed of two ATP-binding proteins (ProV), two transmembrane proteins (ProW) and a solute-binding protein (ProX). Induced in response to increased extracellular osmolarity, this is the first gene of the proU operon (proV-proW-proX). Osmoregulation requires curved DNA downstream of the transcription start site in this gene, which is repressed when bound by H-NS. H-NS may act indirectly to influence the local topology of the promoter (PubMed:1423593). Belongs to the ABC transporter superfamily.