Fig. 1

The N-terminal variable half of OBV Gc is composed of two domains. a Relative amino acid sequence similarity across 100 OBVs over the glycoprotein precursor. Putative transmembrane regions are indicated as black bars. Three secretion signal peptidase cleavage sites are indicated as filled triangles and an additional protease cleavage site is indicated as an empty triangle⁵². b Crystal structure of the variable region of SBV Gc. The head domain is shown in blue, and the two stalk subdomains are shown in yellow and green. The two carbohydrate chains were not originally part of the structure of this deglycosylated protein, and were added to this illustration based on the crystal structure of the SBV head domain in complex with scFv 1C11 (Fig. 5 and Supplementary Fig. 1). Disulfide bonds are shown in bright green and are numbered sequentially. Secondary-structure elements are labeled with h for helices and s for β strands. c The two stalk subdomains are aligned to each other for structural comparison. They are colored in a gradient from white at their N-terminus to gray at their C-terminus. d Sequence alignment of the variable region of Gc from SBV, OROV, BUNV, and LACV. Secondary-structure elements and sequence numbering of SBV are given above the alignment; disulfide bonds are numbered sequentially below the alignment. Strictly conserved residues are boldfaced, similar residues are boxed. Cysteines involved in disulfide bonds are highlighted on bright green background; N-glycosylation sites are highlighted on white background. Residues at the epitopes of mAbs 1C11 and 4B6 are indicated in magenta and orange font, respectively. Residues at the trimer interfaces of BUNV and LACV are indicated in white font. The sequences of the two stalk subdomains are aligned to each other in the last two rows of the alignment