Structural analysis of the flexibility of the Ubl2 domain within the papain-like protease of SARS-CoV-2

The ubiquitin-like domain 2 (Ubl2) of the SARS-CoV-2 virus is necessary for the stability and catalytic efficiency of its papain-like protease (PLpro). Our crystallographic study reveals that the Ubl2 domain exhibits notable flexibility and can adopt a conformation that places itself away from the PLpro catalytic domain, representing a new conformation from those reported so far for SARS-CoV-1 or SARS-CoV-2. The structural flexibility of Ubl2 could be allosterically related to the stability of the zinc-finger domain.