In contrast to MHV S1-NTD, which binds CEACAM1 but not sugars, BCoV S1-NTD binds a sugar receptor but not CEACAM1. Glycan screen arrays identified Neu5,9Ac2 (5-N-acetyl-9-O-acetylneuraminic acid) as the sugar receptor for BCoV S1-NTD. Although the structure of a sugar-bound BCoV S1-NTD is not available, structure-guided mutagenesis has revealed that the sugar-binding site is located in a pocket surrouned by the core and the ceiling-like structure on top of the core.