The S1-CTD of a SARS-CoV-related Rs3367 bat coronavirus contains two aspargines at the two positions (corresponding to positions 479 and 487 in human SARS-CoV strains). The first aspargine is favorable for human ACE2 binding, and the second is one less favorable. Thus, Rs3367 recognizes human ACE2 but probably less well than the human SARS-CoV. These structural studies of SARS-CoV S1-CTD/ACE2 interactions demonstrate that it is critical to understand viral evolution, cross-species transmission, and epidemics within a detailed structural framework.