Since SARS-CoV-2 and SARS-CoV share the same host cell receptor, it was early questioned whether SARS-CoV-2 retains the same RBD motif of SARS-CoV. SARS-CoV RBD corresponds to residues 306–527 of S protein (Li et al., 2005). Sequence analysis shows that residues 319–541 of SARS-CoV-2 (S319–341) share 73.9% sequence identity with SARS-CoV RBD (Wang et al., 2020). Accordingly, Wang et al. (2020) clearly demonstrated that S319–341 corresponds to SARS-CoV-2 RBD by immunofluorescence microscopy. Indeed SARS-CoV-2 S1 and S319–341 positively colocalized with GFP-tagged ACE2 expressed on cell surface of HEK cells, whereas this interaction did not occur with membrane-expressed hDPP4 (MERS receptor). Additionally, soluble ACE2 inhibited the interaction between viral proteins and ACE2-expressing cells in a dose-dependent manner.