PALMITOYLATION OF SEMLIKI FOREST VIRUS GLYCOPROTEINS IN INSECT CELLS (C6 36) OCCURS IN AN EARLY COMPARTMENT AND IS COUPLED TO THE CLEAVAGE OF THE PRECURSOR P62/

The acylation of the envelope proteins of Semliki Forest virus by palm itic acid in infected mosquito (C6/36) cells was investigated. It is s hown that in these cells palmitic acid was incorporated post-translati onally via hydroxylamine-labile linkages onto cysteines in the inner d omains of the viral envelope proteins. The kinetics of incorporation, however, differed considerably as compared to higher eukaryotic cells. (i) The precursor of the envelope proteins E2 and E3, p 62, was weakl y and incompletely palmitoylated irrespective of the duration of label ing. (ii) Under all conditions tested complete acylation of E2 was del ayed as compared to E1. (iii) Heavy protein complexes were formed cons isting of unacylated p 62 and partially unacylated E1. From this data, we conclude that during the maturation of SFV glycoproteins in mosqui to cells differently acylated intermediates of p 62/E2 exist. Furtherm ore, acylation of p 62/E2 and cleavage of p 62 are coupled events, occ urring in an early compartment and allowing the release of the envelop e oligomers for transport.