HEMAGGLUTININ-ESTERASE PROTEIN (HE) OF MURINE CORONA VIRUS - DVIM (DIARRHEA VIRUS OF INFANT MICE)

The acetylesterase (AE) activity of DVIM (diarrhea virus of infant mic e) was assigned to the haemagglutinin-esterase (HE) protein. The subst rate specificity was examined using the natural substrate bovine subma xillary mucin (BSM) and/or synthetic substrates p-nitrophenylacetate ( p-NiA) and alpha-naphthylacetate (alpha-NA) and compared with several strains of MHV and influenza viruses. The AE of DVIM hydrolyzed the O- acetylester bond of BSM, and the two synthetic substrates p-NiA and al pha-NA in vitro. MHV-S reacted efficiently with both p-NiA and alpha-N A but less with BSM. Influenza virus (C/Miyagi/77) reacted with BSM ef ficiently, however reacted with p-NiA weakly, but not with alpha-NA at all. Thus, the AE-reactivity of DVIM was distinctly different from th at of MHV-S and influenza C virus, suggesting that the AE of HE may ha ve a modified function. Isolation of HE by the treatment with non ioni c detergent NP40, resulted in globules approximately 5 nm in diameter. DVIM-binding proteins were demonstrated in the plasma membrane of mou se intestinal brush-border cells and hepatocytes. The same protein was recognized by MHV-S and MHV-4. The cell membranes obtained from these target tissues were substrates for the AE of DVIM. The biological imp ortance of the HE protein for DVIM is discussed.