Structural And Functional Studies Of Zika Virus Helicase

An unprecedented epidemic of Zika virus?ZIKV?infection has been reported in South and Central America and the Caribbean.Neonatal microcephaly potentially associated with ZIKV infection has already caused a public health emergency of international concern.No specific vaccines or drugs are available to treat ZIKV infection.The ZIKV helicase,which plays a pivotal role in viral RNA replication,is an attractive target for therapy.However,the study of ZIKV helicase is still largely unknown.Therefore,we solved the crystal structure of ZIKV helicase and elucidated the mechanism of ZIKV helicase recongnizing its substrate through a series of Molecular Biology,Structural Biology and Biochemistry methods.First,we determined the crystal structure of ZIKV helicase at 1.8-?resolution.The structure revealed a conserved triphosphate pocket for nonspecific hydrolysis of nucleoside triphosphates across multiple flaviviruses.A positive-charged tunnel has been identified in the viral helicase,which is potentially responsible for accommodation of RNA.This crystal structure of ZIKV helicase provides a structural basis for rational drug design.Further more,we explored the mechanism of ZIKV helicase recongnizing ATP.We determined the crystal structures of ZIKV helicase-ATP-Mn²⁺.This is the first structure of any flavivirus helicase bound to ATP.Comparisons with related flavivirus helicases has shown that although the critical P-loop in the active site has variable conformations among different species,it adopts an identical mode to recognize ATP-Mn²⁺.Last,we explored the mechanism of ZIKV helicase recongnizing its RNA.The structure of ZIKV helicase-RNA we have solved has revealed that upon RNA binding,rotations of the motor domains can cause significant conformational changes.Strikingly,although ZIKV and dengue virus?DENV?apo-helicases share conserved residues for RNA binding,their different manners of motor domain rotations result in distinct individual modes for RNA recognition.It suggests that flavivirus helicases could have evolved a conserved engine to convert chemical energy from nucleoside triphosphate to mechanical energy for RNA unwinding,but different motor domain rotations result in variable RNA recognition modes to adapt to individual viral replication.In conclusion,we determined the crystal structure of ZIKV helicase,which provides a structural basis for rational drug design.We determined the crystal structures of ZIKV helicase-ATP-Mn²⁺and ZIKV helicase-RNA,and explored ZIKV helicase ATPase and RNA unwinding activity.We explaned the mechnisam of ZIKV helicase recongnizing ATP-Mn²⁺and its RNA during the viral replication.