MERS-CoV  S, however, uses domain A to recognize non-acetylated sialoside attachment receptors, which likely promote subsequent binding of domain B (SB) to the entry receptor, dipeptidyl-peptidase 4. SARS-CoV and several SARS-related coronaviruses (SARSr-CoV) interact directly with angiotensin-converting enzyme 2 (ACE2) via SB to enter target cell.