Fig. 1.

High-throughput screening using a ubiquitin-like peptide substrate identifies a PLpro inhibitor. (A) Schematic of the SARS-CoV polyprotein, with cleavage sites of the 2 proteases, PLpro (red) and 3CLpro (blue), indicated by color-coded arrows and dashed lines. Nsp numbering is indicated below the polyprotein. (B) The sequences of the 3 PLpro polyprotein cleavage sites are aligned with the peptide substrate used for high-throughput screening. Conserved residues are shown in bold. (C) Results from screening 50,080 compounds in duplicate for inhibition of PLpro activity. The replicate plot shows the percentage inhibition of PLpro by each compound. The structure of the lead compound 7724772 is shown, and its activity is plotted in red. The hit zone for the assay (>35% inhibition) is indicated by a white box.