The surface protein of Marburg virus (GP) is modified by acylation, as
shown by labeling with [H-3]myristic and [H-3]palmitic acid. Acylatio
n of GP also occurred when it was expressed in insect cells with the b
aculovirus expression system. Gas chromatographic analyses of the boun
d fatty acids indicated that exogenously added [H-3]myristic acid was
partly metabolized to palmitic and stearic acid. To elucidate the natu
re of the fatty acid bond, [H-3]palmitic acid-labeled GP was treated w
ith mercaptoethanol. Since the fatty acids were removed by this treatm
ent, it is concluded that the linkage is of the thioester type. A puta
tive attachment site for thioester-linked fatty acids consisting of tw
o cysteine residues located between the transmembrane anchor and the c
arboxy-terminal cytoplasmic tail of GP (Cys(671) and Cys(673)) could b
e identified. Site-directed mutagenesis of these two amino acids to al
anine residues clearly demonstrated that both cysteines could serve as
acylation sites. (C) 1995 Academic Press, Inc.