The OPT family of oligopeptide transporters is distinct from the ABC pfam00005 and PTR pfam00854 transporter families. OPT transporters were first recognized in fungi (Candida albicans and Schizosaccharomyces pombe), but this alignment also includes orthologues from Arabidopsis thaliana. OPT transporters are thought to have 12-14 transmembrane domains and contain the following motif: SPYxEVRxxVxxxDDP.