The structural topologies of MHV S1-NTD and human galectins are identical, except that MHV S1-NTD contains two additional β-strands in one of the β-sheet layers. Compared with human galectins, MHV S1-NTD contains additional structural motifs on top of the core  that form a ceiling-like structure. The outer surface of this ceiling-like structure functions as RBM by binding to the VBM on the N-terminal Ig-like domain of CEACAM1.