Part of the binding-protein-dependent transport system for oligopeptides; probably responsible for the translocation of the substrate across the membrane. Also required for sporulation and competence. Present in detergent-resistant membrane (DRM) fractions that may be equivalent to eukaryotic membrane rafts; these rafts include proteins involved in signaling, molecule trafficking and protein secretion. Positively regulated by TnrA under nitrogen-limited conditions. Belongs to the binding-protein-dependent transport system permease family. OppBC subfamily. Truncated N-terminus.