Discovery And Molecular Mechanism Of Novel Anti-Zika Virus Drugs Targeting NS5 MTase

Zika virus(ZIKV)is a flavivirus and arbovirus related to neurological complications and microcephaly of fetuses and newborns.Until July 2019,87 countries and territories had reported the transmission of ZIKV.However,for ZIKV infection treatment no specific drugs is available now[1].In this study,the important non-structual protein methyltransferase(MTase)of the virus was selected as the anti-ZIKV drug target.After establishing a screening system basing on the luminescence signal for MTase inhibitors,about 2000 compounds in the natural product compound library,bioactive compound library and anti-infection compound library were screened.Two inhibitors,theaflavin(IC50=10.10μM)and epigallocatechin gallate(IC50=5.23 μM)were found with good inhibitory activity.Molecular docking results showed that both compounds had a hydrogen bond with MTase at the 146th amino acid Asp(D146)located in the active cavity.When D146 mutated to alanine,the IC50 of both compounds raised sharply.However,when K105 mutated to alanine,the IC50 of both compounds raised slightly.These results primarily proved that D146 was the key amino acid which affected the interaction between compound and MTase.The surface plasmon resonance experiment reflects the strength of the intermolecular bonding through the response unit(RU)and equilibrium dissociation constant(KD).After WT-MTase was mutated to D146A-MTase,the RU signal of theaflavin and epigallocatechin gallate decreased significantly,and the KD value increased by 4 or 3 times,respectively,which furtherly proved that D146 was the key amino acid that affected the interaction between compound and MTase.Theaflavin showed good antiviral activity against ZIKV in vitro,with EC50 of 8.19μM.Epigallocatechin gallate showed compromising in vitro antiviral activity with EC50 of 71.36μM.Above all,by establishing MTase inhibitor screening system,we screened and found that theaflavin and epigallocatechin gallate could inhibit MTase activity.It was speculated that theaflavin and epigallocatechin gallate inhibited the MTase activity by binding to D146.Theaflavin and epigallocatechin gallate possessed satisfying anti-ZIKV activity.