Purification of the MglC/E membrane proteins of the binding protein-dependent galactose transport system of Salmonella typhimurium.

The high affinity galactose transport system of Salmonella typhimurium consists of four proteins, a periplasmic galactose binding protein (the MglB protein), and three inner membrane-associated proteins, the MglA, MglC and MglE proteins. We purified the MglC/E proteins from an MglC/E hyperproducing strain after solubilisation of inclusion bodies in guanidine hydrochloride followed by renaturation in a detergent-containing buffer and affinity chromatography on a MglB-Sepharose column. The MglC/E proteins are devoid of ATPase activity and they complement an extract from a strain carrying a plasmid with the mglA gene for reconstitution of the MglB-dependent galactose transport in proteoliposomes.