Treponema pallidum, the bacterium that causes syphilis, is an obligate human parasite. T. pallidum lacks the machinery for the de novo synthesis of many key nutrients therefore it acquires these nutrients from its human host. MglB-2 from T. pallidum has been shown to act as the ligand-binding element of an ABC transporter for D-glucose. The overall fold of MglB-2 resembles those of LBPs (Ligand-binding proteins sometimes called 'Periplasmic Binding Proteins') that serve as receptors for nutrients and cofactors in bacterial ABC transporters. Furthermore, structural analysis of MglB-2 i found in Treponema pallidum shows it to be one of the founding member of a family of proteins related to the 'Type I' or 'Cluster B' LBPs [1]. This domain can also be found on the C-terminal region of Pfam:PF13407.

1: The Tp0684 (MglB-2) Lipoprotein of Treponema pallidum: A Glucose-Binding Protein with Divergent Topology. Brautigam CA, Deka RK, Liu WZ, Norgard MV; PLoS One. 2016;11:e0161022. PMID:27536942