Influence of sodium ions on detergent solubilization of pig brush border D-glucose transport system for reconstitution experiments.

The D-glucose uptake by liposomes resulting from the association of egg lecithins with solubilized membrane proteins was measured in order to assess their sodium dependent D-glucose transport activity. Membrane proteins were extracted by Triton X-100 solubilization of pig kidney brush border membrane vesicles, which were suspended either in KCl medium or in NaCl medium. When measured by equilibrium isotope exchange procedure in sodium conditions, the D-glucose uptake by sodium detergent extract associated to liposomes occurred with a higher velocity than that obtained with liposomes reconstituted from potassium detergent extract. No differences were observed in the permeability or in the protein content of two types of liposomes. These results are discussed in terms of activation of D-glucose transport system induced by sodium ions before membrane protein solubilization.