Envelope lipids regulate the in vitro assembly of the HIV-1 capsid

During maturation of type 1 human immunodeficiency virus, a fraction of the capsid protein (CA) molecules in the budding virus particle form a conical capsid. However, the location and role of the remaining CA molecules are unknown. It has been recently reported that the C-terminal domain of CA is able to interact with lipid bilayers, suggesting that the CA molecules that do not form the capsid could be attached to the lipid envelope of the virus. Here, we have studied in vitro the effect of different envelope lipids on the CA polymerization process. Our results show that the negatively charged lipids phosphatidic acid and phosphatidylserine partially inhibit CA polymerization, whereas the nonbilayer forming lipid phosphatidylethanolamine facilitates CA assembly. These results suggest that specific lipids of the viral envelope could have a regulatory role in the maturation of type 1 human immunodeficiency virus.