Figure 5. The severe acute respiratory syndrome coronavirus (SARS-CoV) main protease (Mpro) dimer structure complexed with a substrate–analog hexapeptidyl chloromethyl ketone inhibitor.

(A) The SARS-CoV Mpro dimer structure is presented as ribbons, and inhibitor molecules are shown as ball-and-stick models. Promoter A (the catalytically competent enzyme) is red, promoter B (the inactive enzyme) is blue and the inhibitor molecules are yellow. The N-finger residues of promoter B are green. The molecular surface of the dimer is superimposed. (B) A cartoon diagram illustrating the important role of the N-finger in both dimerization and maintenance of the active form of the enzyme. Reprinted with permission from [27].