Identification of a Coronavirus Hemagglutinin-Esterase with a Substrate Specificity Different from Those of Influenza C Virus and Bovine Coronavirus

Abstract

We have characterized the hemagglutinin-esterase (HE) of puffinosis virus (PV), a coronavirus closely related to mouse hepatitis virus (MHV). Analysis of the cloned gene revealed approximately 85% sequence identity to HE proteins of MHV and approximately 60% identity to the corresponding esterase of bovine coronavirus. The HE protein exhibited acetylesterase activity with synthetic substratesp-nitrophenyl acetate, α-naphthyl acetate, and 4-methylumbelliferyl acetate. In contrast to other viral esterases, no activity was detectable with natural substrates containing 9-O-acetylated sialic acids. Furthermore, PV esterase was unable to remove influenza C virus receptors from human erythrocytes, indicating a substrate specificity different from HEs of influenza C virus and bovine coronavirus. Solid-phase binding assays revealed that purified PV was unable to bind to sialic acid-containing glycoconjugates like bovine submaxillary mucin, mouse α1macroglobulin or bovine brain extract. Because of the close relationship to MHV, possible implications on the substrate specificity of MHV esterases are suggested.

Jumping species—a mechanism for coronavirus persistence and survival

“…While the majority of accessory proteins are thought to be acquired from the host, recent work suggests that novel CoV proteins can even be taken from other pathogens [50]. Identification of a novel coronavirus (Ro-BatCoV GCCDC1) also revealed the presence of a unique 3 0 protein with homology to a known reovirus gene; a similar finding with the hemaglutinin-esterase in a subset of CoV further suggests the possibility of recombination events occurring between viral families [8,51]. Together, the results indicate that CoVs can sample, acquire, and maintain a range of diverse proteins that may be critical for maintenance in natural hosts and emergence in new species.…”

Molecular Interactions in the Assembly of Coronaviruses

“…The protein contains hemagglutinin and acetyl esterase activities (Brian et al, 1995). While the HE proteins of BCoV, HEV, and HCoV-OC43 hydrolyze the 9-O-acetyl group of sialic acid and therefore appear to function as receptor-destroying enzymes (Schultze et al, 1991b;Vlasak et al, 1988a), the HE proteins of MHVlike coronaviruses function as sialate-4-O-acetylesterases (Klausegger et al, 1999;Regl et al, 1999;Wurzer et al, 2002). Although inhibition of the esterase activity of BCoV resulted in a 100-to 400-fold reduction in viral infectivity (Vlasak et al, 1988a), it was shown both for BCoV and for an MHV strain expressing an HE gene that the S protein is required and sufficient for infection (Gagneten et al, 1995;Popova and Zhang, 2002).…”

Common RNA replication signals exist among group 2 coronaviruses: evidence for in vivo recombination between animal and human coronavius molecules

“…Sequence analysis of the leader fusion region of DI RNA progeny from cells infected with HCoV-OC43 helper virus and transfected with reporter-containing BCoV DI RNA. The HCoV-OC43-specific bases G60 and A95 and the BCoV-specific base C133 show that the progeny DI RNA molecule possesses a leader derived from the HCoV-OC43 helper virus and that the recombination site exists somewhere between nts 95 and 133. used to grow SDAV-681 as previously described (Yoo et al, 2000) and mouse L cells were used to grow PV as previously described (Klausegger et al, 1999).…”

“…For PV, purified genomic RNA was reverse transcribed employing oligonucleotide Ada3(ϩ). The second strand was synthesized and cloned as described previously (Klausegger et al, 1999). The resulting plasmids were sequenced by automated DNA sequencing.…”

“…Members of group 3 share identity with the avian infectious bronchitis virus (IBV) and include IBV and turkey enteric coronavirus (TCoV) (Enjuanes et al, 2000;Guy, 2000). Coronaviruses likely to become officially classified as group 2 members on the basis of antigenic relatedness and genome sequence similarities include human enteric coronavirus-4408 (HECoV-4408) (Zhang et al, 1994), puffinosis virus (PV) (Klausegger et al, 1999), and equine enteric coronavirus (ECoV) .…”