Fig. 9.

The unique properties of the Zika NS2B-NS3 protease. Two-dimensional ¹H-¹⁵N NMR HSQC spectra of the Zika NS3 protease domain in the isolated state (A), and in complex with the NS2B cofactor (B). (C) Superimposition of HSQC spectra of the ¹⁵N-labeled Zika NS2B in the isolated state (blue) and in complex with the unlabeled NS3 protease domain (red). (D) Superimposition of HSQC spectra of the ¹⁵N-labeled Zika NS2B in the isolated state (blue), and in complex with unlabeled NS3pro in the presence of unlabelled bovine pancreatic trypsin inhibitor (BPTI) at a molar ratio of 1:2 (red). (E) The crystal structure of the open state of the Zika NS2B-NS3 protease complex (PDB ID of 5T1V). (F) A proposed diagram showing the conformational transformation of NS2B from the open to closed states as triggered by complexing with BPTI. Blue arrows are used for indicating β-strands formed over NS2B, while purple dashed lines are for flexible regions of NS2B.