Nipah Virus V Protein Binding Alters MDA5 Helicase Folding Dynamics

[Image: see text] Nipah virus (NiV) is an emerging and deadly zoonotic paramyxovirus that is responsible for periodic epidemics of acute respiratory illness and encephalitis in humans. Previous studies have shown that the NiV V protein antagonizes host antiviral immunity, but the molecular mechanism is incompletely understood. To address this gap, we biochemically characterized NiV V binding to the host pattern recognition receptor MDA5. We find that the C-terminal domain of NiV V (V(CTD)) is sufficient to bind the MDA5(SF2) domain when recombinantly co-expressed in bacteria. Analysis by hydrogen–deuterium exchange mass spectrometry (HDX-MS) studies revealed that NiV V(CTD) is conformationally dynamic, and binding to MDA5 reduces the dynamics of V(CTD). Our results also suggest that the β-sheet region in between the MDA5 Hel1, Hel2, and Hel2i domains exhibits rapid HDX. Upon V(CTD) binding, these β-sheet and adjacent residues show significant protection. Collectively, our findings suggest that NiV V binding disrupts the helicase fold and dynamics of MDA5 to antagonize host antiviral immunity.