The sialate-4-O-acetylesterases of coronaviruses related to mouse hepatitis virus: a proposal to reorganize group 2 Coronaviridae.
Group 2 coronaviruses are characterized within the order Nidovirales by a unique genome organization. A characteristic feature of group 2 coronaviruses is the presence of a gene encoding the haemagglutinin-esterase (HE) protein, which is absent in coronaviruses of groups 1 and 3. At least three coronavirus strains within group 2 expressed a structural protein with sialate-4-O-acetylesterase activity, distinguishing them from other members of group 2, which encode an enzyme specific for 5-N-acetyl-9-O-acetylneuraminic acid. The esterases of mouse hepatitis virus (MHV) strains S and JHM and puffinosis virus (PV) specifically hydrolysed 5-N-acetyl-4-O-acetylneuraminic acid (Neu4,5Ac2) as well as the synthetic substrates p-nitrophenyl acetate, 4-methylumbelliferyl acetate and fluorescein diacetate. The K(m) values of the MHV-like esterases for the latter substrates were two- to tenfold lower than those of the sialate-9-O-acetylesterases of influenza C viruses. Another unspecific esterase substrate, alpha-naphthyl acetate, was used for the in situ detection of the dimeric HE proteins in SDS-polyacrylamide gels. MHV-S, MHV-JHM and PV bound to horse serum glycoproteins containing Neu4,5Ac2. De-O-acetylation of the glycoproteins by alkaline treatment or incubation with the viral esterases resulted in a complete loss of recognition, indicating a specific interaction of MHV-like coronaviruses with Neu4,5Ac2. Combined with evidence for distinct phylogenetic lineages of group 2 coronaviruses, subdivision into subgroups 2a (MHV-like viruses) and 2b (bovine coronavirus-like viruses) is suggested.
Wurzer
Walter Juergen
WJ
Austrian Academy of Sciences, Institute of Molecular Biology, Department of Biochemistry, Billrothstrasse 11, A-5020 Salzburg, Austria1.
Obojes
Karola
K
Austrian Academy of Sciences, Institute of Molecular Biology, Department of Biochemistry, Billrothstrasse 11, A-5020 Salzburg, Austria1.
Vlasak
Reinhard
R
Austrian Academy of Sciences, Institute of Molecular Biology, Department of Biochemistry, Billrothstrasse 11, A-5020 Salzburg, Austria1.
D000115:Acetylesterase; D000818:Animals; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism*; D002417:Cattle; D003332:Coronaviridae / Q000145:classification* / Q000201:enzymology*; D006023:Glycoproteins / Q000378:metabolism; D006389:Hemagglutinins, Viral / Q000378:metabolism; D006801:Humans; D051379:Mice; D006517:Murine hepatitis virus / Q000145:classification / Q000201:enzymology*; D019158:N-Acetylneuraminic Acid / Q000378:metabolism; D051381:Rats; D013379:Substrate Specificity; D014760:Viral Fusion Proteins / Q000378:metabolism
D006023:Glycoproteins; D006389:Hemagglutinins, Viral; D014760:Viral Fusion Proteins; C060814:hemagglutinin esterase; D002265:Carboxylic Ester Hydrolases; D000115:Acetylesterase; C046298:sialate O-acetylesterase; D019158:N-Acetylneuraminic Acid