A Structural And Dynamic Analysis Of The Partially Disordered Polymerase-Binding Domain In Rsv Phosphoprotein

The phosphoprotein P of Mononegavirales (MNV) is an essential co-factor of the viral RNA polymerase L. Its prime function is to recruit L to the ribonucleocapsid composed of the viral genome encapsidated by the nucleoprotein N. MNV phosphoproteins often contain a high degree of disorder. In Pneumoviridae phosphoproteins, the only domain with well-defined structure is a small oligomerization domain (P-OD). We previously characterized the differential disorder in respiratory syncytial virus (RSV) phosphoprotein by NMR. We showed that outside of RSV P-OD, the intrinsically disordered N-and C-terminal regions displayed a structural and dynamic diversity ranging from random coil to high helical propensity. Here we provide additional insight into the dynamic behavior of P-C alpha, a domain that is C-terminal to P-OD and constitutes the RSV L-binding region together with P-OD. By using small phosphoprotein fragments centered on or adjacent to P-OD, we obtained a structural picture of the P-OD-P-C alpha region in solution, at the single residue level by NMR and at lower resolution by complementary biophysical methods. We probed P-OD-P-C alpha inter-domain contacts and showed that small molecules were able to modify the dynamics of P-C alpha. These structural properties are fundamental to the peculiar binding mode of RSV phosphoprotein to L, where each of the four protomers binds to L in a different way.