The worldwide outbreak of severe acute respiratory syndrome (SARS) in 2003 had caused a high rate of mortality. Main protease (M-Pro) of SARS-associated coronavirus (SARS-CoV) is an important target to discover pharmaceutical compounds for the therapy of this life-threatening disease. During the course of screening new anti-SARS agents, we have identified that a series of unsymmetrical aromatic disulfides inhibited SARS-CoV M-Pro significantly for the first time. Herein, 40 novel unsymmetrical aromatic disulfides were synthesized chemically and their biological activities were evaluated in vitro against SARS-CoV M-Pro. These novel compounds displayed excellent IC50 data in the range of 0.516-5.954 mu M. Preliminary studies indicated that these disulfides are reversible and mpetitive inhibitors. A possible binding mode was generated via molecular docking simulation and a comparative field analysis (CoMFA) model was constructed to understand the structure-activity relationships. The present research therefore has provided some meaningful guidance to design and identify anti-SARS drugs with totally new chemical structures. (C) 2017 Elsevier Masson SAS. All rights reserved.

Human coronavirus NL63 mainly infects younger children and causes cough, fever, rhinorrhoea, bronchiolitis and croup. It encodes two polyprotein precursors required for genome replication and transcription. Each polyprotein undergoes extensive proteolytic processing, resulting in functional subunits. This process is mainly mediated by its genome-encoded main protease, which is an attractive target for antiviral drug design. In this study, the main protease of human coronavirus NL63 was crystallized in complex with a Michael acceptor. The complex crystals diffracted to 2.85 Å resolution and belonged to space group P41212, with unit-cell parameters a = b = 87.2, c = 212.1 Å. Two molecules were identified per asymmetric unit.

Feline infectious peritonitis virus (FIPV) causes a lethal systemic granulomatous disease in wild and domestic cats around the world. Currently, no effective vaccines or drugs have been developed against it. As a member of the genus Alphacoronavirus, FIPV encodes two polyprotein precursors required for genome replication and transcription. Each polyprotein undergoes extensive proteolytic processing, resulting in functional subunits. This process is mainly mediated by its genome-encoded main protease, which is an attractive target for antiviral drug design. In this study, the main protease of FIPV in complex with a Michael acceptor-type inhibitor was crystallized. The complex crystals diffracted to 2.5 Å resolution and belonged to space group I422, with unit-cell parameters a = 112.3, b = 112.3, c = 102.1 Å. There is one molecule per asymmetric unit.

Porcine epidemic diarrhea virus (PEDV) mainly infects neonatal pigs, resulting in significant morbidity and mortality. Owing to problems such as long periods of virus shedding, existing vaccines cannot provide complete protection from PEDV infection. The PEDV genome encodes two polyprotein precursors required for genome replication and transcription. Each polyprotein undergoes extensive proteolytic processing, resulting in functional subunits. This process is mainly mediated by its genome-encoded main protease, which is an attractive target for antiviral drug design. In this study, the main protease of Porcine epidemic diarrhea virus in complex with a Michael acceptor was crystallized. The complex crystals diffracted to 2.5 Å resolution and belonged to space group R3, with unit-cell parameters a = 175.3, b = 175.3, c = 58.7 Å. Two molecules were identified per asymmetric unit.

Human coronavirus HKU1 (HCoV-HKU1), which mainly causes acute self-limited respiratory-tract infections, belongs to group A of the Betacoronavirus genus. Coronavirus genomes encode 16 nonstructural proteins (nsp1–16), which assemble into a large replication–transcription complex mediating virus propagation. Nonstructural protein 9, which binds to the single-stranded DNA/RNA, has been shown to be indispensible for viral replication. Interestingly, a functional mutant (N60K) of nsp9 was identified to compensate for a 6 nt insertion mutation of the 3′-untranslated region (UTR), which is critical for viral RNA synthesis. It has been proposed that the N60K mutation may cause certain conformational changes of nsp9 to rescue the defective insertion mutant. To further investigate the underlying structural mechanism, the N60K mutant of nsp9 from HCoV-HKU1 was successfully crystallized in this study. The crystals diffracted to 2.6 Å resolution and belonged to space group P 2 1 2 1 2 1 , with unit-cell parameters a = 31.9, b = 85.0, c = 95.0 Å. Two molecules were identified per asymmetric unit.

Alanine racemase (Alr(MB4)), a dimeric PLP-dependent thermostable enzyme from the anaerobic eubacterium Thermoanaerobacter tengcongensis MB4, was expressed and purified with a His(6) tag in a form suitable for X-ray crystallographic analysis. Crystals were grown by the hanging-drop vapour-diffusion method at 289 K using a solution consisting of 0.1 M bis-tris pH 7.0, 22%(w/v) polyethylene glycol 4000. X-ray diffraction data were collected to 2.6 Å resolution. The crystal belonged to the orthorhombic space group P2(1)2(1)2(1), with two protein molecules in an asymmetric unit.