PHOSPHOLIPIDS OF SEMLIKI FOREST VIRUS GROWN IN CULTURED MOSQUITO CELLS

The phospholipids of Semliki Forest virus grown in mosquito cells (Aedes albopictus) were analyzed radiochemically. The ratio of 32P-labeled phospholipids to total 32P-label in the virus grown in mosquito cells equilibrated with radiophosphorus was 0.558 .+-. 0.021. This value was similar to the lipid phosphorus:total P ratio (0.539 .+-. 0.025) of the virus grown in the BHK [baby hamster kidney] cells. An average virion of the 2 types of Semliki Forest virus apparently contains approximately the same number of phospholipid molecules. Phosphatidylethanolamine (62%), phosphatidylcholine (14%), phosphatidylserine (10%) and the ethanolamine analog of sphingomyelin, ceramide phosphoethanolamine (9%) were the principal phospholipids in the mosquito cell-grown virus. Comparison with the lipids of virus grown in BHK cells revealed that 2/3 of the polar structures were dissimilar. Surface labeling with formylmethionyl[35S]sulfone methylphosphate suggests that a relatively large fraction of ceramide phosphoethanolamine is located in the outer half of the lipid bilayer of the viral membrane.