Purification and reconstitution of functional lactose carrier from Escherichia coli.
The lactose carrier protein of Escherichia coli was purified by a simple procedure employing differential solubilization and ion-exchange chromatography and reconstituted into liposomes by octylglucoside dilution. The proteoliposomes exhibited both membrane potential-driven lactose transport and lactose counterflow. Furthermore, the purified protein was identified as the product of the lac y gene. These and other results demonstrate that the lactose carrier is the only polypeptide species essential for energy-coupled lactose transport and counterflow.
D000596:Amino Acids / Q000032:analysis; D002462:Cell Membrane / Q000201:enzymology; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D007700:Kinetics; D008564:Membrane Potentials; D026901:Membrane Transport Proteins / Q000302:isolation & purification* / Q000378:metabolism; D008970:Molecular Weight; D009004:Monosaccharide Transport Proteins; D027981:Symporters
D000596:Amino Acids; D029968:Escherichia coli Proteins; C050221:LacY protein, E coli; D026901:Membrane Transport Proteins; D009004:Monosaccharide Transport Proteins; D027981:Symporters; C021499:lactose permease