VP5 protein is one of the two proteins (with VP2) which constitute the virus particle outer capsid. Acts as a membrane permeabilization protein that mediates release of viral particles from endosomal compartments into the cytoplasm. Permeabilization activity is probably negatively regulated by VP2 and is triggered by endosomal degradation of VP2 and exposure to low pH. Belongs to the orbivirus VP5 family.