The furin cleavage site in SARS-Cov-2 does not appear in any other SARS-related beta coronavirus (sarbecovirus).
> Such furin-mediated activation is unusual in that it occurs in part during virus entry. Our findings may explain the polytropic nature, pathogenicity, and life cycle of this zoonotic coronavirus.
MERS-CoV uses furin cleavage of S1/S2 but it does not bind to ACE2 like SARS-CoV-2.