Figure 5.

Structure of the SARS-CoV PL^pro deubiquitinase ([81^••]; PDB code 2FE8). The 62-residue N-terminal region forms a distinct ubiquitin-like domain (right-hand side). The other three domains form an extended right-handed architecture with thumb, palm and finger regions. The active site comprises a catalytic Cys–His–Asp triad (labeled), the cysteine of which is contributed by the thumb domain and the two other residues by the palm domain. The tip of the finger domain (left-hand side) has a structural zinc ion that is ligated by four cysteine sidechains.