The crystal structures of  β-genus MERS-CoV S1-CTD by itself and in complex with human DPP4 provided another view of coronavirus S1 and S1/receptor complex. Like SARS-CoV S1-CTD, MERS-CoV S1-CTD also contains a core structure and a RBM. The core structures of MERS-CoV and SARS-CoV S1-CTDs are highly similar to each other, but their RBMs are markedly different, leading to different receptor specificities.