Erythrosomes: large proteoliposomes derived from crosslinked human erythrocyte cytoskeletons and exogenous lipid.

Large (3-micrometers diameter) mechanically stable proteoliposomes (erythrosomes) were prepared in good yield by coating crosslinked erythrocyte cytoskeletons with phosphatidylcholine. The erythrosomes consist of the polypeptides designated band 1, 2, 3, 4.1 + 4.2, and 5 (less than 4% of the endogenous lipid) and enough added lipid to form a bilayer coating the surface. Electron microscopy shows only the large proteoliposomes in sealed preparations. The trapping of bovine serum albumin, mannitol, sucrose, glucose, cytosine arabinoside, and sodium in the erythrosomes was demonstrated, yielding an apparent volume of up to 100 liters/mol of phospholipid. This preparation possesses an effective diffusion barrier to glucose, sucrose, and sodium ion with half-equilibration times of 34, 29, and 170 hr, respectively. The results of the present study suggest that erythrosomes may be useful for membrane transport protein reconstitution and encapsulation systems.