Fig. 5.

Architecture of particles of members of the order Nidovirales: electron micrographs (A) and schematic representations (B). N, nucleocapsid protein; S, spike protein; M, membrane protein; E, envelope protein; HE, hemagglutinin-esterase. Coronavirus M protein interacts with the N protein. In arterivirus, GP5 and M are major envelope proteins, while GP2, GP3, GP4, and E are minor envelope proteins. Toro- and roniviruses lack the E protein present in corona- and arteriviruses. An equivalent of the M protein has not yet been identified in roniviruses (although see also Fig. 3). This figure was reproduced from Fig. 20.1 presented in Snijder et al. (2005b). Images were reproduced (with permission) from (Snijder and Muelenberg, 1998) (arterivirus), (Spann et al., 1995) (ronivirus), Dr. Fred Murphy, Centers for Disease Control and Prevention (CDC), Atlanta, USA (coronavirus) and (Weiss et al., 1983) (torovirus).