Targeting peptide‐mediated interaction between the N‐protein and P‐protein of human pediatric respiratory syncytial virus by molecular design of chemically stapled helical peptides

Abstract Background Human respiratory syncytial virus (hRSV) is a leading viral etiologic agent of pediatric lower respiratory infection in infants, young children, and immunocompromised elderly individuals. Objective Targeting the intermolecular interaction between the viral nucleocapsid protein (N‐protein) and phosphoprotein (P‐protein) has been recognized as a promising therapeutic strategy against hRSV infection, which is a so‐called peptide‐mediated protein/protein interaction (PmPPI) by binding the short C‐terminal tail of P‐protein to the globular domain of N‐protein. Methods The PmPPI dynamics behavior and thermodynamics property were investigated systematically by integrating computational simulations and experimental assays. Results It is revealed that the C‐terminal tail of P‐protein is intrinsically disordered in free state but would fold into a structured helix when binding to N‐protein, known as coupled folding‐upon‐binding, thus incurring a considerable entropy penalty upon the binding. Several flexible P‐peptide segments with different lengths were derived from the C‐terminus of P‐protein and then stapled chemically by using an all‐hydrocarbon bridge, which effectively constrained the peptide disordered conformation into an ordered helical form in free state, thus considerably improving their affinity to N‐protein by minimizing the unfavorable entropy penalty. Conclusions Electrostatic contribution is primarily responsible for N/P complex stability, while other noncovalent factors such as hydrogen bond and aromatic stacking confer specificity to the complex recognition. The Phe241 residue at the C‐terminal end of P‐protein plays a crucial role that anchors the flexible C‐terminal tail of P‐protein to a druggable pocket on N‐protein surface.