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The nonstructural small glycoprotein sGP of Ebola virus is secreted as an antiparallel-orientated homodimer
V A Volchkova1, H Feldmann, H D Klenk
1Institut für Virologie, Philipps-Universität, Robert-Koch-Strasse 17, Marburg, D-35037, Germany. volchkov@mailer.uni-marburg.de
Abstract:
The nonstructural small glycoprotein sGP, which unlike the transmembrane GP is synthesized from primary nonedited mRNA species, is secreted from infected cells as a disulfide-linked homodimer. Site-directed mutagenesis of all cysteine residues revealed that dimerization is due to an intermolecular disulfide linkage between cysteine residues at positions 53 and 306. Formic acid hydrolysis of sGP demonstrated that sGP dimers consist of monomers in antiparallel orientation. Another editing product of the GP gene of Ebola virus (ssGP), which shares 295 amino-terminal amino acid residues with sGP, is secreted from cells in a monomeric form due to the lack of the carboxyl-terminal part (present in sGP), including cysteine at position 306.
Insights
Ebola virus small glycoprotein (sGP) forms disulfide-linked dimers through cysteines 53 and 306. These sGP monomers are antiparallel, unlike the monomeric ssGP lacking key residues.
Area of Science:
- Virology
- Molecular Biology
- Protein Chemistry
Background:
- The Ebola virus glycoprotein (GP) gene produces multiple products, including the secreted small glycoprotein (sGP).
- sGP is synthesized from non-edited mRNA and secreted as a homodimer, distinct from the transmembrane GP.
- Another editing product, ssGP, shares N-terminal residues with sGP but is secreted as a monomer.
Purpose of the Study:
- To elucidate the structural basis of sGP homodimerization.
- To identify the specific cysteine residues involved in sGP disulfide linkage.
- To understand the structural differences between sGP and ssGP secretion products.
Main Methods:
- Site-directed mutagenesis of all cysteine residues in sGP.
- Analysis of sGP dimerization and disulfide bond formation.
- Formic acid hydrolysis to determine monomer orientation within the dimer.
- Comparison of sGP and ssGP structures and secretion forms.
Main Results:
- sGP dimerization is mediated by an intermolecular disulfide linkage between cysteine residues at positions 53 and 306.
- Formic acid hydrolysis revealed that sGP monomers are arranged in an antiparallel orientation within the dimer.
- The secreted ssGP is monomeric due to the absence of the carboxyl-terminal region, including cysteine 306.
Conclusions:
- The specific cysteine residues 53 and 306 are critical for the disulfide-linked antiparallel dimerization of Ebola virus sGP.
- The structural difference in the C-terminus explains the differential secretion of sGP (dimeric) and ssGP (monomeric) forms.
- Understanding sGP structure provides insights into Ebola virus pathogenesis and potential therapeutic targets.