Asymmetry of influenza virus membrane bilayer demonstrated with phospholipase C

Abstract

IN the red cell, the membrane carbohydrates¹, proteins^2–9 and lipids^9–15 are all unequally distributed between the two sides of the plasma membrane. The membrane proteins and carbohydrates of influenza virions are also asymmetrically distributed^16,17 (review in ref. 18). We have now found that the phospholipids of influenza viriong are asymmetrically distributed as well. Using phospholipase C (PLase C) to digest the phospholipids exposed on the outer surface We have found a predominance of phosphatidyl choline (PC) and sphingomyelin (Sph) on the outer surface and a predominance of phosphatidyl ethanolamine (PE) and phosphytidyl serine (PS) on the inner surface. Since influenza virions acquire theif lipid bilayer by budding out from the membrane of their host cells, it is reasonable to surmise that this asymmetry characterises the host cell plasma membrana as well. Thus, the consistency between our present findings and pevious findings with red cell membranes^9–15 suggest an asymmetric phospholipid distribution of this type mayi be a general feature of plasma membrane Structure.