Proteins containing this domain were originally annotated as basic membrane lipoproteins [1]. However, several proteins containing this domain were later predicted as ABC transporter substrate-binding proteins, such as PnrA (also known as TmpC or TP0319) and RfuA (also known as Tpn38 or TP0298) from Treponema pallidum. PnrA transports purine nucleosides [3], while RfuA transports riboflavin [4]. Proteins containing this domain also include Med from Bacillus subtilis. Med was annotated as a transcriptional activator protein that regulates comK [2]. This domain can also found at the N terminus of glutamate receptor-like proteins from Dictyostelium (slime mold) [5].

1: Heterogeneity of BmpA (P39) among European isolates of Borrelia burgdorferi sensu lato and influence of interspecies variability on serodiagnosis. Roessler D, Hauser U, Wilske B; J Clin Microbiol 1997;35:2752-2758. PMID:9350727

2: A new Bacillus subtilis gene, med, encodes a positive regulator of comK. Ogura M, Ohshiro Y, Hirao S, Tanaka T; J Bacteriol 1997;179:6244-6253. PMID:9335269

3: The PnrA (Tp0319; TmpC) lipoprotein represents a new family of bacterial purine nucleoside receptor encoded within an ATP-binding cassette (ABC)-like operon in Treponema pallidum. Deka RK, Brautigam CA, Yang XF, Blevins JS, Machius M, Tomchick DR, Norgard MV; J Biol Chem. 2006;281:8072-8081. PMID:16418175

4: Evidence for an ABC-type riboflavin transporter system in pathogenic spirochetes. Deka RK, Brautigam CA, Biddy BA, Liu WZ, Norgard MV; MBio. 2013;4:e00615-e00612. PMID:23404400

5: GrlJ, a Dictyostelium GABAB-like receptor with roles in post-aggregation development. Prabhu Y, Muller R, Anjard C, Noegel AA; BMC Dev Biol. 2007;7:44. PMID:17501984