Sequence Cluster id id2 desc organism isHeteromeric 1 Singleton1 TCDB::Q93A34 3.A.1.12.8 BilEB aka OpuBB protein, component of A proline/glycine betaine uptake system. Also reported to be a bile exclusion system that exports oxgall and other bile compounds, BilEA/EB or OpuBA/BB (required for normal virulence) Listeria monocytogenes heteromer 2 Singleton2 TCDB::Q9RQ05 3.A.1.12.5 BusAB aka OPUABC, component of Uptake system for glycine-betaine (high affinity) and proline (low affinity) (OpuAA-OpuABC) or BusAA-ABC of Lactococcus lactis). BusAA, the ATPase subunit, has a C-terminal tandem cystathionine β-synthase (CBS) domain which is the cytoplasmic K+ sensor for osmotic stress (osmotic strength)while the BusABC subunit has the membrane and receptor domains fused to each other (Biemans-Oldehinkel et al., 2006; Mahmood et al., 2006; Gul et al. 2012). An N-terminal amphipathic α-helix of OpuA is necessary for high activity but is not critical for biogenesis or the ionic regulation of transport Lactococcus lactis heteromer