Substrate binding domain of ABC-type glycine betaine transport system
Part of a high affinity multicomponent binding-protein-dependent transport system involved in bacterial osmoregulation. This domain is often fused to the permease component of the transporter complex. Family members are often integral membrane proteins or predicted to be attached to the membrane by a lipid anchor. Glycine betaine is involved in protection from high osmolarity environments for example in Bacillus subtilis. The family member OpuBC is closely related, and involved in choline transport. Choline is necessary for the biosynthesis of glycine betaine. L-carnitine is important for osmoregulation in Listeria monocytogenes. Family also contains proteins binding l-proline (ProX), histidine (HisX) and taurine (TauA).