Role of disordered regions beyond the binding motif of the measles virus NTAIL

The Measles virus nucleocapsid is made of thousands of nucleoprotein (N) repeats, which hold the viral RNA in a helical structure. The last 125 amino acids of each N repeat (NTAIL) are intrinsically disordered and protrude radially outward from the nucleocapsid. NTAIL promotes virus replication by binding to the XD domain of the phosphoprotein P (PXD), which in turn brings the viral polymerase close to the nucleocapsid, where it transcribes and replicates the viral RNA. Only 18 amino acids of NTAIL directly bind to PXD via coupled folding and binding. The majority of NTAIL, on either side of this molecular recognition region (MoRE), remains disordered. While it has been shown that these disordered regions dampen the binding affinity, interactions involving these regions, and their possible functional role have not been identified.