Immobilization of lipid vesicles on polymer support via an amphiphilic peptidic anchor: Application to a membrane enzyme

To immobilize lipid vesicles on a polymer support, we have used a peptidic anchor with the following sequence: Ala-Ala-Leu-Leu-Leu-Ala-Ala-Ala-Ala-Ala -Ala-Ala-Ala-Ala-Ala-Ala-Ala-Ala-Ala-Ala-Ala-Ala-Ala-Ala-Trp-Lys-Lys-Lys-Ly s-Lys-Lys. This amphiphilic peptide was previously de signed in our group t o interact spontaneously and strongly with vesicles without perturbing thei r permeability. At the end of the solid-phase peptide synthesis, the peptid e was left on the polymer beads and this novel polymer-peptide system was u sed for vesicle immobilization. It was shown that this polymer-peptide syst em could immobilize as much as 200 mu mol of lipids per gram of dry resin. The amount of immobilized vesicles was decreased by a reduction of the prop ortion of the negatively charged lipids in the vesicles, indicating the imp ortance of electrostatic interactions in the immobilization of the vesicles . The integrity of the vesicles was mostly preserved after the immobilizati on. This new polymer-peptide system was used easily and successfully to imm obilize a membrane-bound enzyme, gamma-glutamyl transpeptidase. The activit y of the membrane-bound enzyme was studied by monitoring the release of p-n itroaniline. The activity of the enzyme was still retained, even after bein g re-used eight times, indicating the strong immobilization of the enzyme i n its active form. The polymer-peptide support could be regenerated by wash ing with ethanol and reused.