Acylation of the Marburg virus glycoprotein

The surface protein of Marburg virus (GP) is modified by acylation, as shown by labeling with [3H]myristic and [3H]palmitic acid. Acylation of GP also occurred when it was expressed in insect cells with the baculovirus expression system. Gas chromatographic analyses of the bound fatty acids indicated that exogenously added [3H]myristic acid was partly metabolized to palmitic and stearic acid. To elucidate the nature of the fatty acid bond, [3H]palmitic acid-labeled GP was treated with mercaptoethanol. Since the fatty acids were removed by this treatment, it is concluded that the linkage is of the thioester type. A putative attachment site for thioester-linked fatty acids consisting of two cysteine residues located between the transmembrane anchor and the carboxy-terminal cytoplasmic tail of GP (Cys671 and Cys673) could be identified. Site-directed mutagenesis of these two amino acids to alanine residues clearly demonstrated that both cysteines could serve as acylation sites.