| Assay Method Information | |
| | SARS-CoV-2 Coronavirus 3C Protease FRET Assay |
| Description: | The proteolytic activity of the main protease, 3CLpro, of SARS-CoV-2 was monitored using a continuous fluorescence resonance energy transfer (FRET) assay. The SARS-CoV-23CLpro assay measures the activity of full length SARS-CoV-23CL protease to cleave a synthetic fluorogenic substrate peptide with the following sequence: Dabcyl-KTSAVLQ-SGFRKME-Edans modelled on a consensus peptide (V. Grum-Tokars et al. Evaluating the 3C-like protease activity of SARS-coronavirus: recommendations for standardized assays for drug discovery. Virus Research 133 (2008) 63 73). The fluorescence of the cleaved Edans peptide (excitation 340 nm / emission 490 nm) is measured using a fluorescence intensity protocol on a Flexstation reader (Molecular Devices). The fluorescent signal is reduced in the present of PF-835231, a potent inhibitor of SARS-CoV-23CLpro. The assay reaction buffer contained 20 mM Tris-HCl (pH 7.3), 100 nM NaCl, 1 mM EDTA and 25 µM peptide substrate. Enzyme reactions were initiated with the addition of 15 nM SARS-CoV-23CL protease and allowed to proceed for 60 minutes at 23 oC. Percent inhibition or activity was calculated based on control wells containing no compound (0% inhibition/100% activity) and a control compound (100% inhibition/0% activity). IC50 values were generated using a four-parameter fit model using ABASE software (IDBS). Ki values were fit to the Morrison equation with the enzyme concentration parameter fixed to 15 nM, the Km parameter fixed to 14 µM and the substrate concentration parameter fixed to 25 µM using ABASE software (IDBS). |
| Affinity data for this assay | |
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