An integrated system has been developed for discovering potent inhibitors of severe acute respiratory syndrome coronavirus 3C-like protease pro ) by virtual screening correlating with surface plasmon resonance (SPR) and fluorescence resonance energy transfer (FRET) technologies-based assays. The authors screened 81,287 small molecular compounds against SPECS database by virtual screening; 256 compounds were subsequently selected for biological evaluation. Through SPR technology-based assay, 52 from these 256 compounds were discovered to show binding to SARS-CoV 3CLpro . The enzymatic inhibition activities of these 52 SARS-CoV 3CL pro binders were further applied to FRET-based assay, and IC 50 values were determined. Based on this integrated assay platform, 8 new SARS-CoV 3CL pro inhibitors were discovered. The fact that the obtained IC 50 values for the inhibitors are in good accordance with the discovered dissociation equilibrium constants (K D s) assayed by SPR implied the reliability of this platform. Our current work is hoped to supply a powerful approach in the discovery of potent SARS-CoV 3CL pro inhibitors, and the determined inhibitors could be used as possible lead compounds for further research. ) is an attractive target for the discovery of anti-SARS agents for its functional importance in the viral life cycle. To date, varied kinds of SARS-CoV 3CL pro inhibitors were discovered, 4-6 although no effective SARS-CoV 3CL pro inhibitor has yet been reported to treat SARS. Therefore, it is still a great challenge to explore new chemical classes of
SARS-CoV 3CLpro inhibitors that can be possibly used in anti-SARS research.As has been used in the current drug-discovery process, by using the high-performance computation technique to search the large chemical compound databases for the identification of possible drug candidates, the virtual screening approach is a technology that is based on the 3D structure of the target protein. It involves the rapid fitting of the chemical library members into the active sites of 3D protein structures and is critical to distinguish active from inactive substances at the primary screening stage. To date, there have been successful cases of virtual screening used in the discovery of lead compound candidates. For example, we recently reported that by using virtual screening technology with other methods, several new, small molecular specific cyclophilin A inhibitors were discovered 7 ; through virtual screening with surface plasmon resonance (SPR) technology against a database containing structural information of more than 8000 available drugs, Cinanserin (SQ 10,643), a well-characterized serotonin antagonist that had undergone preliminary clinical testing in humans in the 1960s, was discovered to be the SARS-CoV 3CL pro inhibitor.
5Recently, SPR technology has been recognized as a powerful tool in monitoring receptor-ligand interactions with advantages of no-labeling, real-time, noninvasive measurements and low sample