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

Similarities in substrate specificity suggest that it is feasible to create a broad-spectrum inhibitor that targets all 3CL pro . A broadspectrum inhibitor is desirable for a first line defense against coronaviral infection because CoVs are capable of generating novel strains with high virulence through high frequency of mutations and recombination [34, 35, 36, 37] .. Based on the autocleavage sequence of SARS-CoV 3CL pro (i.e. AVLQQ), Rao and co-workers designed broad-spectrum peptidomimetic inhibitors that can inhibit 3CL pro from different groups of CoVs [20] . Their results are consistent with our observation that the autocleavage sequence of SARS-CoV 3CL pro can be well cleaved by all 3CL pro . The substrate preferences profiled in this study will provide a rational basis to improve the broad-spectrum 3CL pro inhibitors. For example, by combining favorable substitutions at P3 to P5 positions, we identified a substrate sequence 'VARLQQSGF' that can be cleaved with high relative activities by 3CL pro from all groups of CoVs (Table 1 ). This substrate sequence may serve as a good starting point of the design of broadspectrum peptidomimetic inhibitors for 3CL pro .