| 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-2 3CLpro assay measures the activity of full-length SARS-CoV-2 3CL 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-2 3CLpro. The assay reaction buffer contained 20 mM Tris-HCI (pH 7.3), 100 nM NaCI, 1 mM EDTA and 25 μM peptide substrate. Enzyme reactions were initiated with the addition of 15 nM SARS-CoV-2 3CL protease and allowed to proceed for 60 minutes at 23 °C. 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). ICso values were generated using a four-parameter fit model using ABASE software (I DBS). 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 (I DBS).Proteolytic activity of SARS-CoV-2 Coronavirus 3CL protease is measured using a continuous fluorescence resonance energy transfer assay. The SARS-CoV-2 3CLpro FRET assay measures the protease catalyzed cleavage of TAMRA-SITSAVLQSGFRKMK-(DABCYL)-OH to TAMRA - SITSAVLQ and SGFRKMK(DABCYL)-OH. The fluorescence of the cleaved TAMRA (ex. 558 nm / em.581 nm) peptide was measured using a TECAN SAFI RE fluorescence plate reader over the course of 10 min. Typical reaction solutions contained 20 mM HEPES (pH 7.0), 1 mM EDTA, 4.0 mM FRET substrate, 4% DMSO and 0.005% Tween-20. Assays were initiated with the addition of 25 nM SARS 3CLpro (nucleotide sequence 9985-10902 of the Urbani strain of SARS coronavirus complete genome sequence (NCBI accession number AY278741)). |
| Affinity data for this assay | |
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