Mechanistic insights into Zika virus NS3 helicase inhibition by Epigallocatechin-3-gallate: Supplementary Files

Deepak Kumar; Nitin Sharma; Murali Aarthy; Sanjeev Singh; Rajanish Giri

Like other flavivirus helicases, ZIKV helicase also belongs to SF2 (Superfamily) family and a phylogenetically close relative of Murray Valley encephalitis virus (MVEV), DENV4, and DENV2 (18) . Full-length NS3 protein has N-terminal protease activity, and C-terminal is associated with helicase activity. ZIKV NS3 helicase (172-617 residues) is a large protein containing three domains where domain 1 (residues175-332) and domain 2 (residues 333-481) forms NTPase pocket and domain 3 (residues 481-617) in association with domain 1 and 2 forms RNA binding tunnel (21) . Though ZIKV helicase is well structured, active sites at NTPase and RNA binding pockets contain highly flexible or disordered P-loop (193-203 residues) and RNA binding loop (244-255 residues) respectively, which are critical for their specific function (21, 22) . In general, past decade has evidenced the significance contribution of intrinsically disordered proteins/regions (IDRs/IDPs) in almost all biological processes and the regions are considered as novel therapeutic targets (23) (24) (25) (26) (27) (28) (29) . Despite the conversed active site amino acid residues among flavivirus helicases, ZIKV helicase show different motor domain movements and RNA binding modes when compared to DENV helicase (21) . These vital functions of ZIKV helicase encourage to screen for antiviral molecules against its active sites. In a recent study, we have determine the inhibitory potential of a small molecule (HCQ) against ZIKV protease with computational and enzyme kinetics studies (30) . Therefore, in this article, we have used molecular docking and simulation approach to find out a significant binding cavity for EGCG. Further, we have verified our computational findings by in vitro enzyme assay to probe the significant binding of EGCG at NTPase site of ZIKV helicase.