Conformational change study of dengue virus NS2B-NS3 protease using 19F NMR spectroscopy

• 19F NMR spectroscopy provides a simple and useful tool to study NS2B-NS3p conformation change.
• The conformational changes of NS2B-NS3p were pH and ligand binding dependent.
• Charge interactions play important roles in the interaction between NS2Bc and NS3p.
• H51A mutation loses the pH dependence of the conformational change.

The dengue virus NS2B-NS3 protease (NS2B-NS3p), an important antiviral target for drug development, has been reported to adopt an open or closed conformation in crystal structures with different NS2B C-terminus (NS2Bc) positioning. In solution, nevertheless, NS2B-NS3p forms a mixture of open, closed and maybe other intermediate conformations, which is difficult to characterize using conventional biophysical and biochemical techniques. In this study, we developed a new strategy to analyze these conformational changes using 19F NMR spectroscopy. Low pH or bovine pancreatic trypsin inhibitor (BPTI) binding promote the conformation change from open to closed, showing the importance of charge forces in the interaction between NS2Bc and NS3p. The mutation H51A impairs the charge interaction and the pH dependence of the conformational changes. It stabilizes the open conformation, while the addition of BPTI still converts NS2B-NS3p from open to closed conformation.