Solution conformations of Zika NS2B-NS3pro and its inhibition by natural products from edible plants
(A) Residue specific (ΔCα-ΔCβ) chemical shifts of the isolated Zika NS2B. (B) Secondary structure score obtained by analyzing chemical shifts with the SSP program. A score of +1 is for the well-formed helix while a score of -1 for the well-formed extended strand. (C) Superimposition of 1H-15N HSQC spectra of 15N-labeled NS2B alone (blue) and 15N-labeled NS2B in complex with unlabeled NS3pro (red). The green is used to highlight two residues Gly57 and Gly69, which could only be detected in the HSQC spectrum of NS2B in the free state. (D) Superimposition of 15N-labeled NS2B alone (blue) and 1H-15N HSQC spectra of 15N-labeled NS2B in complex with unlabeled NS3pro in the presence of unlabelled bovine pancreatic trypsin inhibitor (BPTI) at a molar ratio of 1:2 (red). NMR spectra were acquired at 25°C in 10 mM sodium phosphate buffer at pH 6.5. A proposed diagram showing the conformations of NS2B in the open conformation (E) and in the close conformation (F) 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, whose HSQC peaks could be detected.