Coronaviruses recognize a variety  of host receptors. Although HCoV-NL63 and SARS-CoV belong to the α-genus and β-genus, respectively, their S1-CTDs recognize the same receptor, angiotensin-converting enzyme 2 (ACE2). Although HCoV-NL63, TGEV, and PRCV all belong to the α-genus, their S1-CTDs recognize different receptors-TGEV and PRCV S1-CTDs both recognize aminopeptidase N (APN). Similarly, although SARS-CoV and MERS-CoV both belong to the β-genus, their S1-CTDs recognize different receptors-MERS-CoV S1-CTD recognize dipeptidyl peptidase 4 (DPP4). Although MHV and BCoV both belong to the β-genus, their S1-NTDs recognize carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) and sugar, respectively. In addition, the S1-NTDs of α-genus TGEV and γ-genus IBV also recognize  sugar.