Sodium-stimulated active transport of aminoisobutyric acid by reconstituted vesicles from partially purified plasma membranes of mouse fibroblasts transformed by simian virus 40.

Plasma membrane fractions isolated from mouse fibroblast BALB/c 3T3 cells transformed by simian virus 40 were partially purified by treatment with dimethylmaleic anhydride followed by extraction with 2% cholate. The extracted proteins were combined with exogenous phospholipids and eluted through a Sephadex G50 column. Reconstituted vesicles thus obtained were shown to possess the ability of Na+-stimulated transport of alpha-aminoisobutyric acid. The simultaneous addition of NaSCN and alpha-aminoisobutyric acid to these vesicles produced a transient accumulation above the equilibrium level (overshoot, active transport). The Na+-stimulated transport of alpha-aminoisobutyric acid was sensitive to the accompanying anion and to the temperature of incubation. The results demonstrate that partially purified membrane proteins of mouse fibroblast cells can be incorporated into the liposomes that have the characteristics of Na+-stimulated and electrochemically sensitive active transport of alpha-aminoisobutyric acid.