Article

Structural basis for antiviral inhibition of the main protease, 3C, from human enterovirus 93.

Institute for Research in Biomedicine, Barcelona, Spain.
Journal of Virology (Impact Factor: 5.08). 08/2011; 85(20):10764-73. DOI: 10.1128/JVI.05062-11
Source: PubMed

ABSTRACT Members of the Enterovirus genus of the Picornaviridae family are abundant, with common human pathogens that belong to the rhinovirus (HRV) and enterovirus (EV) species, including diverse echo-, coxsackie- and polioviruses. They cause a wide spectrum of clinical manifestations ranging from asymptomatic to severe diseases with neurological and/or cardiac manifestations. Pandemic outbreaks of EVs may be accompanied by meningitis and/or paralysis and can be fatal. However, no effective prophylaxis or antiviral treatment against most EVs is available. The EV RNA genome directs the synthesis of a single polyprotein that is autocatalytically processed into mature proteins at Gln↓Gly cleavage sites by the 3C protease (3C(pro)), which has narrow, conserved substrate specificity. These cleavages are essential for virus replication, making 3C(pro) an excellent target for antivirus drug development. In this study, we report the first determination of the crystal structure of 3C(pro) from an enterovirus B, EV-93, a recently identified pathogen, alone and in complex with the anti-HRV molecules compound 1 (AG7404) and rupintrivir (AG7088) at resolutions of 1.9, 1.3, and 1.5 Å, respectively. The EV-93 3C(pro) adopts a chymotrypsin-like fold with a canonically configured oxyanion hole and a substrate binding pocket similar to that of rhino-, coxsackie- and poliovirus 3C proteases. We show that compound 1 and rupintrivir are both active against EV-93 in infected cells and inhibit the proteolytic activity of EV-93 3C(pro) in vitro. These results provide a framework for further structure-guided optimization of the tested compounds to produce antiviral drugs against a broad range of EV species.

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    ABSTRACT: We have determined the cleavage specificity and the crystal structure of the 3C protease of enterovirus 68 (EV68 3C(pro)). The protease exhibits a typical chymotrypsin fold with a Cys…His…Glu catalytic triad; its three-dimensional structure is closely related to that of the 3C(pro) of rhinovirus 2 as well as to that of poliovirus. The phylogenetic position of the EV68 3C(pro) between the corresponding enzymes of rhinoviruses on the one hand and enteroviruses on the other prompted us to use the crystal structure for the design of irreversible inhibitors, with the goal of discovering broad-spectrum antiviral compounds. We synthesized a series of peptidic α,β-unsaturated ethyl esters of increasing length and for each inhibitor candidate, we determined a crystal structure of its complex with the EV68 3C(pro), which served as the basis for the next design round. To exhibit inhibitory activity, compounds must span at least P3 to P1' ; the most potent inhibitors comprise P4 to P1' . Inhibitory activities were found against the purified 3C protease of EV68 as well as with replicons for poliovirus and EV71 (EC(50) = 0.5 μM for the best compound). Antiviral activities were determined using cell cultures infected with EV71, poliovirus, echovirus 11, and various rhinovirus serotypes. The most potent inhibitor, SG85, exhibited activity with EC(50) values of ≈180 nM against EV71 and ≈60 nM against human rhinovirus 14 in a live virus-cell-based assay. Even the shorter SG75, spanning only P3 to P1' , displayed significant activity (EC(50) = 2 to 5 μM) against various rhinoviruses.
    Journal of Virology 02/2013; · 5.08 Impact Factor

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