PDB IDs are 3KBH for HCoV-NL63 S1-CTD, 4F5C for PRCV S1-CTD, 2AJF for SARS-CoV S1-CTD, 4KR0 for MERS-CoV S1-CTD, 3R4D for MHV S1-NTD, 4H14 for BCoV S1-NTD, 2IEQ for HCoV-NL63 HRs, 1WYY for SARS-CoV HRs, 4NJL for MERS-CoV HRs, and 1WDF for MHV HRs. HCoV-NL63 and other alpha-coronaviruses recognize different receptors: other alpha-coronaviruses such as TGEV, PEDV, and PRCV recognize another zinc peptidase, aminopeptidase N (APN) (22–25). Similarly, SARS-CoV and other beta-coronaviruses recognize different receptors: MERS-CoV and HKU4 recognize a serine peptidase, dipeptidyl peptidase 4 (DPP4) (26, 27); MHV recognizes a cell adhesion molecule, carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) (28, 29); BCoV and OC43 recognize sugar (30). The alpha-coronaviruses TGEV and PEDV and the gammacoronavirus IBV also use sugar as receptors or coreceptors.