Unique properties of Zika NS2B-NS3pro complexes as decoded by experiments and MD simulations

Zika virus can be passed from a pregnant woman to her fetus, thus leading to birth defects including more than microcephaly. It has been recently estimated that one-third of the world population will be infected by Zika, but unfortunately no vaccine or medicine is available so far. Zika NS2B-NS3pro is essential for its replication and thus represents an attractive target for drug discovery/design. Here we characterized conformation, catalysis, inhibition and dynamics of linked and unlinked Zika NS2B-NS3pro complexes by both experiments and MD simulations. The results unveil the unique properties of Zika NS2B-NS3pro which are very different from Dengue one. Particularly, CD and NMR studies indicate that unlike Dengue, the C-terminal region of Zika NS2B with a significant sequence variation is highly disordered in the open conformation. Indeed, MD simulations reveal that up to 100 ns, the Dengue NS2B C-terminus constantly has close contacts with its NS3pro domain. By a sharp contrast, the Zika NS2B C-terminus loses the contacts with its NS3pro domain after 10 ns, further forming a short {beta}-sheet characteristic of the closed conformation at 30 ns. Furthermore, we found that a small molecule, previously identified as an active site inhibitor for other flaviviral NS2B-NS3pro, inhibited Zika NS2B-NS3pro potently in an allosteric manner. Our study provides the first insight into the dynamics of Zika NS2B-NS3pro and further deciphers that it is susceptible to allosteric inhibition, which thus bears critical implications for the future development of therapeutic allosteric inhibitors.