Vaccinia virus B5R protein (B5R)

The Vaccinia virus B5R protein is a 42-kDa glycosylated type I membrane protein encoded by the B5R open reading frame (ORF). It localizes to the membranes of infected cells and the outer envelope of extracellular enveloped virus (EEV), but not intracellular mature virus (IMV). The protein features a signal peptide, transmembrane domain, cytoplasmic tail, and an extracellular domain with four short consensus repeat (SCR) domains homologous to eukaryotic complement control proteins. B5R is essential for EEV formation, IMV wrapping by intracellular membranes, normal plaque size, actin tail induction, and virus virulence; its deletion causes small plaques in vitro and high attenuation in vivo. The SCR domains are dispensable for EEV formation but conserved across poxviruses, potentially aiding immune evasion via complement regulation. Monoclonal antibodies targeting B5R epitopes (e.g., SCR1-SCR2 regions, stalk) neutralize EEV and inhibit comet tail formation

Other names

B5 protein