Figure 2.

Multiple alignment of the complete env sequences of representative prototypes of the SRV-2 subtypes. A ClustalW alignment was generated using one representative prototype member from each of the six SRV-2 subtype clusters: SRV-2A (D2/CEL/OR), SRV-2B (D2/RHE/ORV1), SRV-2C (442N), SRV-2D (F90346), SRV-2E (A94040), SRV-2F (SRV_sing31.2). The sequences of SRV-1 and SRV-3 were included for comparison. Dots represent amino acids identical to the reference sequence of the SRV-2A prototype. Conserved cysteine residues are shaded in yellow, while putative N-linked glycosylation sites (NXT/S) are shaded in black. The putative signal peptide, known T- and B-cell epitopes, heptad repeat, as well as the gp20 fusion and transmembrane domains are indicated and referenced in the text. A predicted disulfide linkage within the immunosuppressive peptide, and the proteolytic cleaveage sites generating the gp70 surface and gp20 transmembrane subunits are indicated. While B- and T-cell epitopes have been determined for SRV-2, the functions and locations of other domains are derived from studies in SRV-3.