title: Disulfide bond structure determination and biochemical analysis of glycoprotein C from herpes simplex virus.
abstract: A biochemical analysis of glycoprotein C (gC of herpes simplex virus was undertaken to further characterize the structure of the glycoprotein and to determine its disulfide bond arrangement. We used three recombinant forms of gC, gC1(457t), gC1(delta33-123t), and gC2(426t), each truncated prior to the transmembrane region. The proteins were expressed and secreted by using a baculovirus expression system and have been shown to bind to monoclonal antibodies which recognize discontinuous epitopes and to complement component C3b in a dose-dependent manner. We confirmed the N-terminal residues of each mature protein by Edman degradation and confirmed the internal deletion in gC1(delta33-123t). The molecular weight and extent of glycosylation of gC1 (457t), gC1(delta33-123t), and gC2(426t) were determined by treating each protein with endoglycosidases and then subjecting it to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and mass spectrometric analysis. The data indicate that eight to nine of the predicted N-linked oligosaccharide sites on gC1(457t) are occupied by glycans of approximately 1,000 Da. In addition, O-linked oligosaccharides are present on gC1(457t), primarily localized to the N-terminal region (amino acids [aa] 33 to 123) of the protein. gC2(426t) contains N-linked oligosaccharides, but no O-linked oligosaccharides were detected. To determine the disulfide bond arrangement of the eight cysteines of gC1(457t),the protein was cleaved with cyanogen bromide. SDS-PAGE analysis followed by Edman degradation identified three cysteine-containing fragments which are not connected by disulfide linkages. Chemical modification of cysteines combined with matrix-assisted laser desorption ionization mass spectrometry identified disulfide bonds between cysteine 1 (aa 127) and cysteine 2 (aa 144) and between cysteine 3 (aa 286) and cysteine 4 (aa 347). Further proteolysis of the cyanogen bromide-generated fragment containing cysteine 5 through cysteine 8, combined with mass spectrometry and Edman degradation, showed that disulfide bonds link cysteine 5 (aa 386) to cysteine 8 (aa 442) and cysteine 6 (aa 390) to cysteine 7 (aa 419). A similar disulfide bond arrangement is postulated to exist in gC homologs from other herpesviruses.
authors.affiliation: Department of Microbiology, University of Pennsylvania, Philadelphia 19104, USA.
authors.forename: A H
authors.initials: AH
authors.lastname: Rux
authors.forename: W T
authors.initials: WT
authors.lastname: Moore
authors.forename: J D
authors.initials: JD
authors.lastname: Lambris
authors.forename: W R
authors.initials: WR
authors.lastname: Abrams
authors.forename: C
authors.initials: C
authors.lastname: Peng
authors.forename: H M
authors.initials: HM
authors.lastname: Friedman
authors.forename: G H
authors.initials: GH
authors.lastname: Cohen
authors.forename: R J
authors.initials: RJ
authors.lastname: Eisenberg
mesh_terms: D000595:Amino Acid Sequence; D004220:Disulfides; D006801:Humans; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011487:Protein Conformation; D018139:Simplexvirus / Q000737:chemistry*; D014759:Viral Envelope Proteins / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D004220:Disulfides; D014759:Viral Envelope Proteins; C048232:glycoprotein C, herpes simplex virus type 2