Characterization of the interaction of the human respiratory syncytial virus phosphoprotein and nucleocapsid protein using the two-hybrid system.

The interaction between the human respiratory syncytial virus phosphoprotein (P) and nucleocapsid (N) protein has been investigated using the two hybrid system in yeast and in tissue culture cells. Deletion analysis identified two regions in the P protein involved in this interaction. The immediate carboxy-terminal 20 amino acids were essential for interaction with the N protein. Point mutations in this region demonstrated that alteration of two conserved, phosphorylated, serine residues reduced binding to 50% of that of the native protein. The introduction of two proline residues to disrupt the predicted alpha-helical domain in this region dramatically reduced the ability of the mutant P protein to interact with the N protein. A second region which affected the interaction of the two proteins was located adjacent to the essential carboxy-terminal area. Deletion of this second region resulted in an increase in the strength of the interaction between the two proteins. These data shows that the RSV P protein, while having no amino acid sequence identity with the equivalent P protein of other negative strand viruses, is likely to have similar structural and functional features.