Project description:The main protease (M(pro)) of severe acute respiratory syndrome coronavirus (SARS-CoV) plays an essential role in the extensive proteolytic processing of the viral polyproteins (pp1a and pp1ab), and it is an important target for anti-SARS drug development. SARS-CoV M(pro) is composed of a catalytic N-terminal domain and an ?-helical C-terminal domain linked by a long loop. Even though the N-terminal domain of SARS-CoV M(pro) adopts a similar chymotrypsin-like fold as that of piconavirus 3C protease, the extra C-terminal domain is required for SARS-CoV M(pro) to be enzymatically active. Here, we reported the NMR assignments of the SARS-CoV M(pro) N-terminal domain alone, which are essential for its solution structure determination.
Project description:The coronavirus disease 2019 (COVID-19) pandemic has prompted an urgent need for new treatment strategies. No target-specific drugs are currently available for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), but new drug candidates targeting the viral replication cycle are being explored. A prime target of drug-discovery efforts is the SARS-CoV-2 main protease (Mpro). The main proteases of different coronaviruses, including SARS-CoV-2, SARS-CoV and Middle East respiratory syndrome coronavirus (MERS-CoV), share a structurally conserved substrate-binding region that can be exploited to design new protease inhibitors. With the recent reporting of the X-ray crystal structure of the SARS-CoV-2 Mpro, studies to discover Mpro inhibitors using both virtual and in vitro screening are progressing rapidly. This review focusses on the recent developments in the search for small-molecule inhibitors targeting the SARS-CoV-2 Mpro.
Project description:Intrinsically disordered proteins (IDPs) play essential roles in regulating physiological processes in eukaryotic cells. Many viruses use their own IDPs to "hack" these processes to deactivate host defenses and promote viral growth. Thus, viral IDPs are attractive drug targets. While IDPs are hard to study by X-ray crystallography or cryo-EM, atomic level information on their conformational preferences and dynamics can be obtained using NMR spectroscopy. SARS-CoV-2 Nsp2, whose C-terminal region (CtR) is predicted to be disordered, interacts with human proteins that regulate translation initiation and endosome vesicle sorting. Molecules that block these interactions could be valuable leads for drug development. The 13Cβ and backbone 13CO, 1HN, 13Cα, and 15N nuclei of Nsp2's 45-residue CtR were assigned and used to characterize its structure and dynamics in three contexts; namely: (1) retaining an N-terminal His tag, (2) without the His tag and with an adventitious internal cleavage, and (3) lacking both the His tag and the internal cleavage. Two five-residue segments adopting a minor extended population were identified. Overall, the dynamic behavior is midway between a completely rigid and a fully flexible chain. Whereas the presence of an N-terminal His tag and internal cleavage stiffen and loosen, respectively, neighboring residues, they do not affect the tendency of two regions to populate extended conformations.
Project description:SARS coronavirus main protease (M(pro)) plays an essential role in the extensive proteolytic processing of the viral polyproteins (pp1a and pp1ab), and it is an important target for anti-SARS drug development. We have reported that both the M(pro) C-terminal domain alone (M(pro)-C) and the N-finger deletion mutant of M(pro) (M(pro)-Delta7) exist as a stable dimer and a stable monomer (Zhong et al., J Virol 2008; 82:4227-4234). Here, we report structures of both M(pro)-C monomer and dimer. The structure of the M(pro)-C monomer is almost identical to that of the C-terminal domain in the crystal structure of M(pro). Interestingly, the M(pro)-C dimer structure is characterized by 3D domain-swapping, in which the first helices of the two protomers are interchanged and each is enwrapped by four other helices from the other protomer. Each folding subunit of the M(pro)-C domain-swapped dimer still has the same general fold as that of the M(pro)-C monomer. This special dimerization elucidates the structural basis for the observation that there is no exchange between monomeric and dimeric forms of M(pro)-C and M(pro)-Delta7.
Project description:There is an urgent necessity of effective medication against severe acute respiratory syndrome coronavirus 2 (SARS CoV-2), which is producing the COVID-19 pandemic across the world. Its main protease (Mpro) represents an attractive pharmacological target due to its involvement in essential viral functions. The crystal structure of free Mpro shows a large structural resemblance with the main protease of SARS CoV (nowadays known as SARS CoV-1). Here, we report that average SARS CoV-2 Mpro is 1900% more sensitive than SARS CoV-1 Mpro in transmitting tiny structural changes across the whole protein through long-range interactions. The largest sensitivity of Mpro to structural perturbations is located exactly around the catalytic site Cys-145 and coincides with the binding site of strong inhibitors. These findings, based on a simplified representation of the protein as a residue network, may help in designing potent inhibitors of SARS CoV-2 Mpro.
Project description:High-throughput structural genomics projects seek to delineate protein structure space by determining the structure of representatives of all major protein families. Generally this is accomplished by processing numerous proteins through standardized protocols, for the most part involving purification of N-terminally His-tagged proteins. Often proteins that fail this approach are abandoned, but in many cases further effort is warranted because of a protein's intrinsic value. In addition, failure often occurs relatively far into the path to structure determination, and many failed proteins passed the first critical step, expression as a soluble protein. Salvage pathways seek to recoup the investment in this subset of failed proteins through alternative cloning, nested truncations, chemical modification, mutagenesis, screening buffers, ligands and modifying processing steps. To this end we have developed a series of ligation-independent cloning expression vectors that append various cleavable C-terminal tags instead of the conventional N-terminal tags. In an initial set of 16 proteins that failed with an N-terminal appendage, structures were obtained for C-terminally tagged derivatives of five proteins, including an example for which several alternative salvaging steps had failed. The new vectors allow appending C-terminal His(6)-tag and His(6)- and MBP-tags, and are cleavable with TEV or with both TEV and TVMV proteases.
Project description:Herein, we investigate the structure and flexibility of the hydrated SARS-CoV-2 main protease by means of 2.0 μs molecular dynamics (MD) simulations in explicit solvent. After having performed electrostatic pKa calculations on several X-ray structures, we consider both the native (unbound) configuration of the enzyme and its noncovalent complex with a model peptide, Ace-Ala-Val-Leu-Gln∼Ser-Nme, which mimics the polyprotein sequence recognized at the active site. For each configuration, we also study their monomeric and homodimeric forms. The simulations of the unbound systems show that the relative orientation of domain III is not stable in the monomeric form and provide further details about interdomain motions, protomer-protomer interactions, inter-residue contacts, accessibility at the catalytic site, etc. In the presence of the peptide substrate, the monomeric protease exhibits a stable interdomain arrangement, but the relative orientation between the scissile peptide bond and the catalytic dyad is not favorable for catalysis. By means of comparative analysis, we further assess the catalytic impact of the enzyme dimerization, the actual flexibility of the active site region, and other structural effects induced by substrate binding. Overall, our computational results complement previous crystallographic studies on the SARS-CoV-2 enzyme and, together with other simulation studies, should contribute to outline useful structure-activity relationships.
Project description:The Severe Acute Respiratory Syndrome Corona Virus 2 (SARS-CoV-2) pandemic represents a global challenge. SARS-CoV-2's ability to replicate in host cells relies on the action of its non-structural proteins, like its main protease (Mpro). This cysteine protease acts by processing the viruses' precursor polyproteins. As proteases, together with polymerases, are main targets of antiviral drug design, we here have performed biochemical high throughput screening (HTS) with recombinantly expressed SARS-CoV-2 Mpro. A fluorescent assay was used to identify inhibitors in a compound library containing known drugs, bioactive molecules and natural products. These screens led to the identification of 13 inhibitors with IC50 values ranging from 0.2 μM to 23 μM. The screens confirmed several known SARS-CoV Mpro inhibitors as inhibitors of SARS-CoV-2 Mpro, such as the organo-mercuric compounds thimerosal and phenylmercuric acetate. Benzophenone derivatives could also be identified among the most potent screening hits. Additionally, Evans blue, a sulfonic acid-containing dye, could be identified as an Mpro inhibitor. The obtained compounds could be of interest as lead compounds for the development of future SARS-CoV-2 drugs.