The transfer of myristic and other fatty acids on lipid and viral protein acceptors in cultured cells infected with Semliki Forest and influenza virus.

3H]Myristic and 3H]palmitic acid were compared as tracers for the fatty acylation of cellular lipids and viral glycoproteins in chicken embryo cells infected with fowl plague and Semliki Forest virus (SFV). Both of these substrates are incorporated into glycerolipids to a similar extent, whereas sphingolipids show much higher levels of palmitate than myristate after a 20 h labeling period. Both fatty acid species were found to be subject to metabolic conversions into longer chain fatty acids yielding 11.7% C16:0 from 3H]myristic and 11.8% C18:0 from 3H]palmitic acid. The reverse, a metabolic shortening of the exogenous acyl-chains yielding, for instance, significant levels of myristic acid from palmitic acid was not observed. Out of the various 3H]fatty acids present after in vivo labeling with 3H]myristic acid (C14:0) the elongated acyl-species arising from metabolic conversion (e.g., C16:0; C18:0) are preferred over myristic acid in the acylation of SFV E1 and E2 and of the influenza viral hemagglutinin (HA2). During acylation of exogenous E1 from SFV in vitro incorporation of palmitic acid from palmitoyl CoA exceeds that of myristic acid from myristoyl CoA by a factor of 37. This indicates that specificity for the incorporation of fatty acids into viral membrane proteins occurs at the level of the polypeptide acyltransferase(s).