Involved in the uptake of dipeptides and tripeptides. May influence host-pathogen interactions. Involved in motility and agglutination, and has a role in stimulation of dendritic cells. Deletion mutant has a reduced ability to utilize a number of di- and tri-peptides as nitrogen sources, displays reduced motility and reduced agglutination compared to wild type. Belongs to the peptide transporter carbon starvation (CstA) (TC 2.A.114) family.