The SARS-CoV binding  region on the ACE2 surface has been termed virus-binding  motif (VBM). The RBM and VBM complement each other in shape and chemical details. The structure of SARS-CoV S1-CTD/ACE2 complex provided the first view of coronavirus S1 and S1/receptor complex and laid the foundation for future structural and evolutionary comparisons with other  coronavirus S1 and S1/receptor complexes.