Domain-structure of cytoplasmic border region is main determinant for palmitoylation of influenza virus hemagglutinin (H7)

Abstract

We have shown previously that the length of cytoplasmic tails influences the selection of lipid substrates for palmitoylation of influenza viral hemagglutinin esterase fusion (HEF) and hemagglutinin (HA) glycoproteins [Veit et al. (1996) Biochem. J. 318, 163-172; Reverey et al. (1996) J. Biol. Chem. 271, 23607-23610]. Using a series of new chimeric mutant proteins derived from acylated influenza virus HA (subtype H7) and from nonacylated Sendai virus fusion protein (F, strain Z), we report here that palmitoylation levels depend on the type of transmembrane or cytoplasmic domain, or both, present in the expression products and that cysteine residues placed close to the cytoplasmic membrane border are not sufficient for acylation. By inserting stretches of the HA transmembrane domain into a nonacylated mutant of Sendai F (FCys), we induce palmitoylation after expression in CV.1 cells, and the level of fatty acid transfer increases with the length of the HA-derived insert. A five-amino-acid shift of the HA transmembrane domain severely augments fatty acid transfer. Our data suggest that the influenza virus HA contains complex conformational signals for palmitoylation that are mainly located within the transmembrane domain but also involve the C-tail region, whereas the extracellular (luminal) domain has only marginal influence on palmitoylation.