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 phosphorus ratio (0.539 +/- 0.025) of the virus grown in the BHK cells. It is concluded that an average virion of the two types of Semliki Forest virus contains approximately the same number of phospholipid molecules. Phosphatidylethanolamine (62%), phosphatidylcholine (14%), phosphatidylserine (10%) and the ethanolamine analogue of sphingomyelin, ceramide phosphoethanolamine (9%) were the principal phospholipids in the mosquito cell-grown virus. Comparison with the lipids of virus grown in hamster cells (BHK cells) revealed that two-thirds 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.