Structural analysis of the menangle virus p protein reveals a soft boundary between ordered and disordered regions

Abstract

The paramyxoviral phosphoprotein (P protein) is the non-catalytic subunit of the viral RNA polymerase, and coordinates many of the molecular interactions required for RNA synthesis. All paramyxoviral P proteins oligomerize via a centrally located coiled-coil that is connected to a downstream binding domain by a dynamic linker. The C-terminal region of the P protein coordinates interactions between the catalytic subunit of the polymerase, and the viral nucleocapsid hous-ing the genomic RNA. The inherent flexibility of the linker is believed to facilitate polymerase trans-location. Here we report biophysical and structural characterization of the C-terminal region of the P protein from Menangle virus (MenV), a bat-borne paramyxovirus with zoonotic potential. The MenV P protein is tetrameric but can dissociate into dimers at sub-micromolar protein concentra-tions. The linker is globally disordered and can be modeled effectively as a worm-like chain. How-ever, NMR analysis suggests very weak local preferences for alpha-helical and extended beta conformation exist within the linker. At the interface between the disordered linker and the structured C-terminal binding domain, a gradual disorder-to-order transition occurs, with X-ray crystallo-graphic analysis revealing a dynamic interfacial structure that wraps the surface of the binding do-main.