ACE2 and infection: The initial steps of infection involve specific binding of the RBD located in S1 to the peptidase domain of the cell entry receptor angiotensin-converting enzyme 2 (ACE2) [5,15]. Some evidence in the literature has indicated that NTD is also involved in the entry of most coronaviruses, including SARS-CoV-2, but its functional role has yet to be fully defined [16,17].