Molecular mechanism of divalent-metal-induced activation of NS3 helicase and insights into Zika virus inhibitor design

Abstract

Zika virus has attracted increasing attention because of its potential for causing human neural disorders, including microcephaly in infants and Guillain–Barré syndrome. Its NS3 helicase domain plays critical roles in NTP-dependent RNA unwinding and translocation during viral replication. Our structural analysis revealed a pre-activation state of NS3 helicase in complex with GTPγS, in which the triphosphate adopts a compact conformation in the absence of any divalent metal ions. In contrast, in the presence of a divalent cation, GTPγS adopts an extended conformation, and the Walker A motif undergoes substantial conformational changes. Both features contribute to more extensive interactions between the GTPγS and the enzyme. Thus, this study provides structural evidence on the allosteric modulation of MgNTP2− on the NS3 helicase activity. Furthermore, the compact conformation of inhibitory NTP identified in this study provides precise information for the rational drug design of small molecule inhibitors for the treatment of ZIKV infection.

A high ATP concentration enhances the cooperative translocation of the SARS coronavirus helicase nsP13 in the unwinding of duplex RNA

“…These two translational polyproteins are processed autoproteolytically by the major viral cysteine proteases M PRO or 3CL PRO to produce 16 non-structural proteins (nsPs), including RNA-dependent RNA polymerases (RdRp, nsP12) and NTPase/helicase (nsP13) 6-8 . These viral replicases are the core of membrane-bound replication-transcription complexes that synthesize the entire viral genome and eight subgenomic mRNAs 9,10 .Because viral helicase is considered to be essential for subsequent viral replication and proliferation, it is an important potential target for antiviral therapy [11][12][13] . In addition, the inhibition of these targets may interfere with the metabolism of the infecting virus without strong side effects in patients.…”

“…Because viral helicase is considered to be essential for subsequent viral replication and proliferation, it is an important potential target for antiviral therapy [11][12][13] . In addition, the inhibition of these targets may interfere with the metabolism of the infecting virus without strong side effects in patients.…”

In vitro methods for testing antiviral drugs

“…Virus-encoded ATPase-driven helicases have been identified in numerous human pathogens. Helicases from several (+)RNA viruses have been characterized, including NS3 helicases from flaviviruses such as dengue virus, HCV, West Nile virus, yellow fever virus, and Japanese encephalitis virus (Cao et al, 2016;Gu and Rice, 2016;Jain et al, 2016;Lin et al, 2017;Nedjadi et al, 2015;Wu et al, 2005). SARS and MERS coronaviruses encode nsp13 with helicase activity (Adedeji and Lazarus, 2016;Hao et al, 2017;Seybert et al, 2000).…”

The Race To Find Antivirals for Zika Virus

“…This is the case with the N2B-NS3 trypsin-like serine protease, which plays a key role in virus replication by contributing to viral polyprotein processing (30), or with NS3 helicase activity (31). Due to the relevance of NS2B-NS3 function in the ZIKV life cycle, the search for inhibitors of the enzymatic activity of this complex is at the front line of antiviral discovery against ZIKV (30,(32)(33)(34). For instance, taking advantage of a previous work that identified inhibitors of the HCV protease by high-throughput screening of over 40,000 compounds (35), the same group have recently analyzed 71 of these nonpeptidic small molecules against ZIKV and found that 10 of them showed 50% inhibitory concentrations (IC 50 s) lower than 50 M, with IC 50 s of 5.2 M and 4.1 M for compounds 2 and 3, respectively (30).…”