Va. Volchkova et al., Delta-peptide is the carboxy-terminal cleavage fragment of the nonstructural small glycoprotein sGP of Ebola virus, VIROLOGY, 265(1), 1999, pp. 164-171
In the present study we have investigated processing and maturation of the
nonstructural small glycoprotein (sGP) of Ebola virus. When sGP expressed f
rom vaccinia virus vectors was analyzed by pulse-chase experiments using SD
S-PAGE under reducing conditions, the mature form and two different precurs
ors have been identified. First, the endoplasmic reticulum form sGP(er), fu
ll-length sGP with oligomannosidic N-glycans, was detected, sGP(or) was the
n replaced by the Golgi-specific precursor pre-sGP, full-length sGP contain
ing complex N-glycans. This precursor was finally converted by proteolysis
into mature sGP and a smaller cleavage fragment, Delta-peptide. Studies emp
loying site-directed mutagenesis revealed that sGP was cleaved at a multiba
sic amino acid motif at positions 321 to 324 of the open reading frame. Cle
avage was blocked by RVKR-chloromethyl ketone. Uncleaved pre-sGP forms a di
sulfide-linked homodimer and is secreted into the culture medium in the pre
sence of the inhibitor as efficiently as proteolytically processed sGP. In
vitro treatment of pre-sGP by purified recombinant furin resulted in effici
ent cleavage, confirming the importance of this proprotein convertase for t
he processing and maturation of sGP. Delta-peptide is also secreted into th
e culture medium and therefore represents a novel nonstructural expression
product of the GP gene of Ebola virus. Both cleavage fragments contain sial
ic acid, but only Delta-peptide is highly O-glycosylated. (C) 1999 Academic
Press.