Part of the ABC transporter DppABCDF involved in dipeptide transport (PubMed:11409543). Binds di- and tripeptides with high affinity. Requires a free N-terminal alpha-amino group and an alpha-peptide bound contiguous with the N-terminal amino group, has a strong selectivity for L-residues, and shows preference for dipeptides containing methionine or arginine, followed by hydrophobic tripeptides consisting of leucine or valine residues (PubMed:10769143). The complex is composed of two ATP-binding proteins (DppD and DppF), two transmembrane proteins (DppB and DppC) and a solute-binding protein (DppA). Expression is regulated by the peptide content of the growth media. Inactivation of the gene impairs growth on low concentrations of di-valine. Belongs to the bacterial solute-binding protein 5 family.