The Coronavirus Hemagglutinin Esterase Glycoprotein

Abstract

Early reviews on Coronavirus structure (Siddell et al., 1983a,b; Sturman and Holmes, 1985) described coronaviruses as having three major structural proteins: a large-surface (or peplomer) glycoprotein of around 200 kDa, a phos-phorylated nucleocapsid protein of around 50 kDa, and a glycosylated, multi-spanning membrane protein of around 30 kDa. This description was based primarily on studies of the prototypic avian infectious bronchitis virus (IBV) and the highly studied mouse hepatitis virus (MHV), strain A59. Although IBV was shown early on to have a weak hemagglutinating property, detection of the hemagglutinating activity required that the virus first be treated with phospho-lipase C or concentrated by centrifugation in sucrose gradients (Bingham et al., 1975). Not all strains of IBV demonstrated hemagglutination, however, and hemagglutinating activity by IBV, as well as by the porcine transmissible gastroenteritis virus (TGEV) (Noda et al., 1987, 1988) was probably a cryptic property of the spike protein (Cavanagh and Davis, 1986). The nature of this hemagglutinating activity is not well understood.