Members of this family are transmembrane proteins. Several are Leishmania putative proteins that are thought to be pteridine transporters. One such protein Swiss: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 five putative Arabidopsis thaliana proteins of unknown function. 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). Lemley C, Yan S, Dole VS, Madhubala R, Cunningham ML, Beverley SM, Myler PJ, Stuart KD; Mol Biochem Parasitol 1999;104:93-105. PMID:10589984

2: An amplified DNA element in Leishmania encodes potential integral membrane and nucleotide-binding proteins. Myler PJ, Lodes MJ, Merlin G, de Vos T, Stuart KD; Mol Biochem Parasitol 1994;66:11-20. PMID:7984172