This protein is a component of the oligopeptide permease, a binding protein-dependent transport system, It binds peptides up to five amino acids long with high affinity. Also required for sporulation and competence. Interacts with FloT in detergent-resistant membranes (DRM) (PubMed:23651456). Colocalizes rarely with FloT membrane assemblies (PubMed:27362352). 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 bacterial solute-binding protein 5 family.