This family is comprised of systems involved in the transport of apparently unrelated solutes. Analysis of BP sequences led to the identification of 2 non overlapping clusters. The first cluster groups systems involved in the transport of osmoprotectants, consisting of small modified peptides that contain an N,N,N trimethyl ammonium group like glycine-betaine, choline and carnitine ( Pubmed : 9818351 ) , ( Pubmed : 10216873 ) . These transporters display an organization typical of BPD transporters. The OPU transporter of Lactococcus lactis constitutes a remarkable exception to this organization scheme, where an extracytoplasmic domain corresponding to the BP is fused to the C-terminus of the IM ( Pubmed : 10515910 ) . The second cluster is comprised of systems involved in the uptake of nitrate ( Pubmed : 8437564 ) , cyanate ( Pubmed : 9294430 ) , bicarbonate ( Pubmed : 10557362 ) and N-alkylsulfonates ( Pubmed : 10361295 ) .