It is well-known that CoV rely on their spike proteins for binding to a host cell surface receptor -which, in turn, leads to cell invasion. As for SARS-CoV, the particular receptor to which 2019-nCoV binds is angiotensin-converting enzyme 2 (ACE2). Since the spike proteins for the two viruses exhibit no less than 76% sequence identity, they are broadly assumed to adopt similar folded structures. Again, in SARS-CoV, a receptor binding domain -responsible for high-affinity interactions with ACE2 -has already been identified in region S1 of the spike protein (see Ref. for the appropriate nomenclature).