title: Nidovirus sialate-O-acetylesterases: evolution and substrate specificity of coronaviral and toroviral receptor-destroying enzymes.
abstract: Many viruses achieve reversible attachment to sialic acid (Sia) by encoding envelope glycoproteins with receptor-binding and receptor-destroying activities. Toroviruses and group 2 coronaviruses bind to O-acetylated Sias, presumably via their spike proteins (S), whereas other glycoproteins, the hemagglutinin-esterases (HE), destroy Sia receptors by de-O-acetylation. Here, we present a comprehensive study of these enzymes. Sialate-9-O-acetylesterases specific for 5-N-acetyl-9-O-acetylneuraminic acid, described for bovine and human coronaviruses, also occur in equine coronaviruses and in porcine toroviruses. Bovine toroviruses, however, express novel sialate-9-O-acetylesterases, which prefer the di-O-acetylated substrate 5-N-acetyl-7(8),9-di-O-acetylneuraminic acid. Whereas most rodent coronaviruses express sialate-4-O-acetylesterases, the HE of murine coronavirus DVIM cleaves 9-O-acetylated Sias. Under the premise that HE specificity reflects receptor usage, we propose that two types of Sias serve as initial attachment factors for coronaviruses in mice. There are striking parallels between orthomyxo- and nidovirus biology. Reminiscent of antigenic shifts in orthomyxoviruses, rodent coronaviruses exchanged S and HE sequences through recombination to extents not appreciated before. As for orthomyxovirus reassortants, the fitness of nidovirus recombinant offspring probably depends both on antigenic properties and on compatibility of receptor-binding and receptor-destroying activities.
authors.affiliation: Virology Division, Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, 3584 CL Utrecht, The Netherlands.
authors.forename: Saskia L
authors.initials: SL
authors.lastname: Smits
authors.forename: Gerrit J
authors.initials: GJ
authors.lastname: Gerwig
authors.forename: Arno L W
authors.initials: AL
authors.lastname: van Vliet
authors.forename: Arjen
authors.initials: A
authors.lastname: Lissenberg
authors.forename: Peter
authors.initials: P
authors.lastname: Briza
authors.forename: Johannis P
authors.initials: JP
authors.lastname: Kamerling
authors.forename: Reinhard
authors.initials: R
authors.lastname: Vlasak
authors.forename: Raoul J
authors.initials: RJ
authors.lastname: de Groot
mesh_terms: D000123:Acetyltransferases / Q000502:physiology*; D000818:Animals; D001483:Base Sequence; D003332:Coronaviridae / Q000201:enzymology / Q000235:genetics / Q000472:pathogenicity; D019143:Evolution, Molecular; D006389:Hemagglutinins, Viral / Q000502:physiology; D006801:Humans; D008969:Molecular Sequence Data; D028381:Nidovirales / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity; D011991:Receptors, Virus / Q000378:metabolism; D013045:Species Specificity; D013379:Substrate Specificity; D017003:Torovirus / Q000201:enzymology / Q000235:genetics / Q000472:pathogenicity; D014760:Viral Fusion Proteins / Q000502:physiology
chemical_list: D006389:Hemagglutinins, Viral; D011991:Receptors, Virus; D014760:Viral Fusion Proteins; C060814:hemagglutinin esterase; D000123:Acetyltransferases; C099970:sialic acid O-acetyltransferase