The function of the members of this family is unknown, but DctQ homologues are invariably found in the tripartite ATP-independent periplasmic transporters [1].

1: TRAP transporters: an ancient family of extracytoplasmic solute-receptor-dependent secondary active transporters. Rabus R, Jack DL, Kelly DJ, Saier MH Jr; Microbiology 1999;145:3431-3445. PMID:10627041

2: The tripartite ATP-independent periplasmic (TRAP) transporters of bacteria and archaea. Kelly DJ, Thomas GH; FEMS Microbiol Rev 2001;25:405-424. PMID:11524131