Targeting a Binding Pocket within the Trimer-of-Hairpins: Small-Molecule Inhibition of Viral Fusion

• Published in: Proceedings of the National Academy of Sciences - PNAS 2004-10, Vol.101 (42), p.15046-15051
• Main Authors: Cianci, Christopher, Langley, David R., Dischino, Douglas D., Sun, Yaxiong, Yu, Kuo-Long, Stanley, Anne, Roach, Julia, Li, Zhufang, Dalterio, Richard, Colonno, Richard, Meanwell, Nicholas A., Krystal, Mark, Palese, Peter
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino acids; Antiviral Agents - pharmacology; Benzimidazoles - pharmacology; Binding Sites; Biochemistry; Biological Sciences; Cell membranes; Fusion; HIV; Human immunodeficiency virus; Human respiratory syncytial virus; Membrane Fusion - drug effects; Membrane Fusion - physiology; Models, Molecular; Molecular dynamics; Molecular Sequence Data; Molecules; Photoaffinity Labels; Protein Conformation; Proteins; Resins; Respiratory syncytial virus; Respiratory Syncytial Viruses - drug effects; Respiratory Syncytial Viruses - genetics; Respiratory Syncytial Viruses - physiology; Trimers; Viral Fusion Proteins - chemistry; Viral Fusion Proteins - genetics; Viral Fusion Proteins - physiology; Viral morphology; Viruses
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0406696101

Trimeric class I virus fusion proteins undergo a series of conformational rearrangements that leads to the association of C- and N-terminal heptad repeat domains in a "trimer-of-hairpins" structure, facilitating the apposition of viral and cellular membranes during fusion. This final fusion hairpin structure is sustained by protein-protein interactions, associations thought initially to be refractory to small-molecule inhibition because of the large surface area involved. By using a photoaffinity analog of a potent respiratory syncytial virus fusion inhibitor, we directly probed the interaction of the inhibitor with its fusion protein target. Studies have shown that these inhibitors bind within a hydrophobic cavity formed on the surface of the N-terminal heptad-repeat trimer. In the fusogenic state, this pocket is occupied by key amino acid residues from the C-terminal heptad repeat that stabilize the trimer-of-hairpins structure. The results indicate that a low-molecular-weight fusion inhibitor can interfere with the formation or consolidation of key structures within the hairpin moiety that are essential for membrane fusion. Because analogous cavities are present in many class I viruses, including HIV, these results demonstrate the feasibility of this approach as a strategy for drug discovery.