The MOS family systems are involved in the uptake of monosaccharides (pentoses and hexoses) like arabinose ( Pubmed : 2445996 ) , D-allose ( Pubmed : 9401019 ) , galactose ( Pubmed : 1719366 ) , ribose ( Pubmed : 8762140 ) , ( Pubmed : 8762141 ) and xylose. The typical organization of these systems consists in 1 BP, 1 IM and 1 ABC. The ABC subunit is made up of 2 homologous halves, suggesting that a primordial gene duplication and subsequent fusion event occurred in the generation of the ancestral MOS system. In the sequenced genomes B. subtilis, Treponema pallidum, Borrelia burgdorferi, Archeoglobus fulgidus and Aeropyrum pernix, several putative MOS family transporters were identified. However, the putative operons determining these systems were apparently devoid of a typical substrate binding protein. Rather, they were associated with secreted proteins homologous to a family of lipoproteins of unknown function, the so-called basic membrane proteins C (BMPC), which constitute potent immunogens in pathogenic bacteria ( Pubmed : 10715014 ) . Psi-Blast analyses show that these lipoproteins display significant similarity to MOS family substrate binding proteins. At least some BMPC might be involved in the uptake of a yet unidentified monosaccharide.