InterPro domain: IPR039309

Members of this family are transmembrane proteins. Several are Leishmania putative proteins that are thought to be pteridine transporters. One such protein Q25272 , previously termed (and is still annotated as) ORFG, was shown to encode a biopterin transport protein using null mutants [ 1 ], thus being subsequently renamed BT1. The significant similarity of ORFG/BT1 to Trypanosoma brucei ESAG10 (a putative transmembrane protein and another member of this family) was previously noted [ 2 ]. This family also contains folate-biopterin transporters (FBTs) from blue-green algae and plants, including Slr0642 protein from Synechocystis and its plastidial orthologue At2g32040 from Arabidopsis [ 3 ]. Both Slr0642 protein and At2g32040 mediate folate monoglutamate transport involved in tetrahydrofolate biosynthesis. However, this entry also includes seven other Arabidopsis FBT proteins that lack conserved critical residues and may not have folate or pterin transport activity [ 4 ]. In addition, it also contains two predicted prokaryotic proteins (from the cyanobacteria Synechocystis and Synechococcus).

1. The Leishmania donovani LD1 locus gene ORFG encodes a biopterin transporter (BT1). Mol. Biochem. Parasitol. 104, 93-105
2. An amplified DNA element in Leishmania encodes potential integral membrane and nucleotide-binding proteins. Mol. Biochem. Parasitol. 66, 11-20
3. Identification of transport-critical residues in a folate transporter from the folate-biopterin transporter (FBT) family. J. Biol. Chem. 285, 2867-75