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

Department of Microbiology, Mount Sinai School of Medicine, New York, New York 10029-6574.
Journal of Virology (Impact Factor: 4.65). 01/1989; 62(12):4686-90.
Source: PubMed

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.

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Available from: Reinhard Vlasak, Aug 03, 2015
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    • "Several lines of evidence support an important role of the HE protein in BCV infectivity: (i) The HE protein of BCV was shown to induce mAbs that neutralized virus infectivity in vitro (in cell cultures) and in vivo (in animals); four neutralizing epitopes were identified on the HE protein of BCV (Deregt and Babiuk, 1987; Deregt et al., 1989). (ii) Treatment of BCV with inhibitors that specifically inactivate acetylesterase reduced viral infectivity by 3 logs or greater, while the same treatment of influenza A virus did not affect virus infectivity, indicating that acetylesterase activity is required for BCV infectivity (Vlasak et al., 1988). (iii) Both the S and HE proteins of BCV recognized the same receptor-determinant of the cultured cells and erythrocyte (Schultze et al., 1991; Schultze and Herrler, 1992, 1994). "
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    ABSTRACT: The spike (S) and hemagglutinin/esterase (HE) of bovine coronavirus (BCV) are the two envelope proteins that recognize the same receptor-determinant of 9-O-acetylneuraminic acid on host cells. However, the precise and relative roles of the two proteins in BCV infectivity remain elusive. To unequivocally determine their roles in viral cytopathogenicity, we developed a system in which phenotypically chimeric viruses were generated by infecting a closely related mouse hepatitis virus (MHV) in cells that stably express an individual BCV protein (S or HE). The chimeric viruses were then used to infect human rectal tumor (HRT)-18 cells that are permissive to BCV but are nonsusceptible to MHV. Using this approach, we found that the chimeric virus containing the BCV S protein on the virion surface entered and replicated in HRT-18 cells; this was specifically blocked by prior treatment of the virus with a neutralizing antibody specific to the BCV S protein, indicating that the BCV S protein is responsible for initiating chimeric virus infection. In contrast, chimeric viruses that contain biologically active and functional BCV HE protein on the surface failed to enter HRT-18 cells, indicating that the BCV HE protein alone is not sufficient for BCV infection. Taken together, these results demonstrate that the S protein but not the HE protein of BCV is necessary and sufficient for infection of the chimeric viruses in HRT-18 cells, suggesting that BCV likely uses the S protein as a primary vehicle to infect permissive cells.
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    • "(Risco et al., 1996). A fifth component in the envelope of some MHV strains is the 65 kDa HE protein with homologies to haemagglutinin–esterase protein of influenza C virus (Vlasak et al., 1988). It presumably serves a similar role to the influenza viral protein HN in the destruction of the viral receptor following virus entry and release. "
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