Structural and Functional Analysis of the Surface Protein of Human Coronavirus OC43

Abstract

The two surface glycoproteins S and HE of human coronavirus OC43 (HCV-OC43) were isolated from the viral membrane and purified. Only the S protein was able to agglutinate chicken erythrocytes, indicating that this viral protein is the major hemagglutinin of HCV-OC43. The receptor determinant recognized by this virus on the surface of erythrocytes is N-acetyl-9-O-acetylneuraminic acid (Neu5,9Ac2) which is also used by bovine coronavirus for attachment to cells. By analyzing erythrocytes containing different amounts of Neu5,9Ac2 in either of two linkage types, it was found that there are subtle differences in the affinity of both viruses for 9-O-acetylated sialic acid. Bovine coronavirus was more efficient in recognizing low amounts of Neu5,9Ac2 alpha 2,3 linked to galactose, whereas HCV-OC43 was superior with respect to the alpha 2,6 linkage. The gene coding for the S protein of HCV-OC43 was cloned and sequenced. A large open reading frame predicts a polypeptide of 150 kDa in the unglycosylated form. A protein of about 190 kDa is expected if the 20 potential glycosylation sites are used for attachment of N-linked oligosaccharide side chains. These predictions were confirmed by in vitro transcription and translation of the gene in the presence or absence of canine pancreatic microsomal membranes. A high degree of sequence homology was found between the S proteins of HCV-OC43 and bovine coronavirus. Structural and functional analyses of more strains should help to identify the location of the sialic acid-binding site.

Crystal Structure of Bovine Coronavirus Spike Protein Lectin Domain

“…Previous virus infection studies have shown that Neu5,9Ac2 can function as a receptor or co-receptor for BCoV (4,5). However, it is not clear whether any other type of sugar may also have high affinity for BCoV NTD.…”

“…BCoV and HCoV-OC43 recognize a sugar moiety, 5-N-acetyl-9-O-acetylneuraminic acid (Neu5,9Ac2), on cell-surface glycoproteins or glycolipids (4,5). In contrast, MHV does not use sugar as a receptor (6).…”

Effects of Sialic Acid Substitutions on Recognition by Sambucus nigra Agglutinin and Maackia amurensis Hemagglutinin

“…Furthermore, for some lectins, the glycerol-like side chain of sialic acid is essential for recognition and 9-O-acetylation of this side chain can block the interaction (11, 18 -20, 22, 26, 30, 31). In other instances, 9-O-acetylation is required for recognition (11,(32)(33)(34)(35)(36)(37). Here we have evaluated the importance of the N-acyl-and 9-O-acetyl groups of sialic acid for recognition by SNA and MAH.…”

Human-specific Regulation of α2–6-linked Sialic Acids

“…By virtue of forming the "canopy" of the glycocalyx, Sias are recognized and used as attachment sites by a large number and wide variety of microbial pathogens and their toxins. Many Sia-binding proteins of different pathogens have been well characterized and generally show a high degree of specificity for different types of Sias and/or their linkage to the underlying glycan chain (1)(2)(3)(4)(5).…”