2OP9: Substrate Specificity Profiling and Identification of a New Class of Inhibitor for the Major Protease of the SARS Coronavirus

Severe acute respiratory syndrome (SARS) is an emerging infectious disease associated with a high rate of mortality. The SARS-associated coronavirus (SARS-CoV) has been identified as the etiological agent of the disease. Although public health procedures have been effective in combating the spread of SARS, concern remains about the possibility of a recurrence. Various approaches are being pursued for the development of efficacious therapeutics. One promising approach is to develop small molecule inhibitors of the essential major polyprotein processing protease 3Clpro. Here we report a complete description of the tetrapeptide substrate specificity of 3Clpro using fully degenerate peptide libraries consisting of all 160,000 possible naturally occurring tetrapeptides. The substrate specificity data show the expected P1-Gln P2-Leu specificity and elucidate a novel preference for P1-His containing substrates equal to the expected preference for P1-Gln. These data were then used to develop optimal substrates for a high-throughput screen of a 2000 compound small-molecule inhibitor library consisting of known cysteine protease inhibitor scaffolds. We also report the 1.8 A X-ray crystal structure of 3Clpro bound to an irreversible inhibitor. This inhibitor, an alpha,beta-epoxyketone, inhibits 3Clpro with a k3/Ki of 0.002 microM(-1) s(-1) in a mode consistent with the substrate specificity data. Finally, we report the successful rational improvement of this scaffold with second generation inhibitors. These data provide the foundation for a rational small-molecule inhibitor design effort based upon the inhibitor scaffold identified, the crystal structure of the complex, and a more complete understanding of P1-P4 substrate specificity.
PDB ID: 2OP9Download
MMDB ID: 47466
PDB Deposition Date: 2007/1/27
Updated in MMDB: 2007/10
Experimental Method:
x-ray diffraction
Resolution: 1.8  Å
Source Organism:
Similar Structures:
Biological Unit for 2OP9: dimeric; determined by author
Molecular Components in 2OP9
Label Count Molecule
Proteins (2 molecules)
Replicase Polyprotein 1AB (Pp1ab, Orf1ab) 3c-like Proteinase (3cl-pro, 3clp)
Molecule annotation
Chemicals (2 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB