The crystal structure of α-genus S1-CTD complexed with porcine APN illustrated how another similar α-coronavirus  S1-CTD recognizes a different  host receptor. Similarly to the structural relationship between SARS-CoV and MERS-CoV S1-CTDs, PRCV and HCoV-NL63 S1-CTDs also have highly similar core structures. However, their three RBMs are divergent, leading to different receptor specificities. Similarly  to the VBMs on ACE2 and DPP4, the VBMs for PRCV on APN are also located on the outer surface of APN, away from the peptidase active site. Overall, these result suggest that PRCV and HCoV-NL63 S1-CTDs  share an evolutionary origin but have diverged in their RBM loops to recognize different host receptors.