The E3 protein of bovine coronavirus is a receptor-destroying enzyme with acetylesterase activity

Abstract

In addition to members of the Orthomyxoviridae and Paramyxoviridae, several coronaviruses have been shown to possess receptor-destroying activities. Purified bovine coronavirus (BCV) preparations have an esterase activity which inactivates O-acetylsialic acid-containing receptors on erythrocytes. Diisopropyl fluorophosphate (DFP) completely inhibits this receptor-destroying activity of BCV, suggesting that the viral enzyme is a serine esterase. Treatment of purified BCV with [3H]DFP and subsequent sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the proteins revealed that the E3 protein was specifically phosphorylated. This finding suggests that the esterase/receptor-destroying activity of BCV is associated with the E3 protein. Furthermore, treatment of BCV with DFP dramatically reduced its infectivity in a plaque assay. It is assumed that the esterase activity of BCV is required in an early step of virus replication, possibly during virus entry or uncoating.

Porcine hemagglutinating encephalomyelitis virus induces apoptosis in a porcine kidney cell line via caspase-dependent pathways

“…Z-VAD-FMK did not affect the virus titers obtained from PHEV-infected PK-15 cells at 96 h post-infection (Fig. 4D), and hemagglutination assay (HA) was performed to present a kinetics of infection to show that there is no effect of Z-VAD-FMK on viral replication (Vlasak et al, 1988) (data not show). In short, these results suggest that PHEV-induced apoptosis may be caspase dependent and apoptosis is not essential for PHEV replication in vitro and mechanisms other than apoptosis may contribute to the overall CPE caused by PHEV replication in PK-15 cells.…”

Accessory proteins of SARS-CoV and other coronaviruses

“…5). The hemagglutinin-esterases (HEs) are a family of viral envelope glycoproteins that mediate reversible attachment to O-acetylated sialic acids by acting both as receptor-binding (''lectins'') and as receptor-destroying enzymes (RDEs) with esterase activity (Woo et al, 2010;Zhang et al, 1992;Vlasak et al, 1988;Schultze et al, 1991). In coronaviruses, this gene is exclusively present in betacoronaviruses of clade a and has probably been acquired after diverging from the ancestors of other betacoronavirus lineages (Zeng et al, 2008), possibly via horizontal gene transfer from Influenza C virus (Langereis et al, 2012).…”

“…In coronaviruses, this gene is exclusively present in betacoronaviruses of clade a and has probably been acquired after diverging from the ancestors of other betacoronavirus lineages (Zeng et al, 2008), possibly via horizontal gene transfer from Influenza C virus (Langereis et al, 2012). Crystal structures have been determined for the hemagglutinin esterases of BCoV and MHV (Vlasak et al, 1988;Schultze et al, 1991). The E domain (with esterase activity) is found to be highly conserved but the RBD (receptor binding domain) is found to be flexible (Vlasak et al, 1988).…”

“…Crystal structures have been determined for the hemagglutinin esterases of BCoV and MHV (Vlasak et al, 1988;Schultze et al, 1991). The E domain (with esterase activity) is found to be highly conserved but the RBD (receptor binding domain) is found to be flexible (Vlasak et al, 1988). HCoV OC43 and BCoV use 9-O-acetylated sialic acids as receptor to initiate infection, and correspondingly possess sialate-9-O-acetylesterases as RDE.…”

“…Most betacoronaviruses of lineage a attach to 9-O-acetylated sialic acid, but one group of murine coronaviruses has switched to using 4-O-acetylated sialic acid (Schultze et al, 1991). The available crystal structures reveal the adaptations of the RBD to differences in receptor usage (Vlasak et al, 1988;Schultze et al, 1991).…”