Profiling of Substrate Specificities of 3C-Like Proteases from Group 1, 2a, 2b, and 3 Coronaviruses

Chuck, Chi-Pang; Chow, Hak-Fun; Wan, David Chi-Cheong; Wong, Kam-Bo

3C-like protease (3CL pro ), which is also named main protease, is responsible for the processing of the viral polyproteins into at least 15 non-structural proteins, most of which are constituents of the viral replication and transcription complex. The cleavage process can be acted in cis and in trans [19] . This enzyme is a good drug target for anti-coronaviral infection, as inhibiting the autocleavage process can inhibit viral replication and reduce virus-induced cytopathic effects on host cells [20, 21, 22, 23] . A detailed knowledge of substrate specificity of 3CL pro is helpful in the rational design of inhibitors. Substrate specificity of SARS-CoV 3CL pro was extensively investigated after the outbreak of SARS in 2003. Fan et al. measured the protease activity against 34 single-substituted variants at P5 to P1' positions, while Goetz et al. profiled the specificity at P4 to P1 positions by using a fully degenerated library of tetrapeptide mixtures [24, 25] . Chuck et al. profiled the substrate preference of SARS-CoV 3CL pro by measuring the activity of 3CL pro against substrate variants with single substitutions at P5 to P3' positions [26] .