title: Immobilization of the N-terminal helix stabilizes prefusion paramyxovirus fusion proteins.
abstract: Parainfluenza virus 5 (PIV5) is an enveloped, single-stranded, negative-sense RNA virus of the Paramyxoviridae family. PIV5 fusion and entry are mediated by the coordinated action of the receptor-binding protein, hemagglutinin-neuraminidase (HN), and the fusion protein (F). Upon triggering by HN, F undergoes an irreversible ATP- and pH-independent conformational change, going down an energy gradient from a metastable prefusion state to a highly stable postfusion state. Previous studies have highlighted key conformational changes in the F-protein refolding pathway, but a detailed understanding of prefusion F-protein metastability remains elusive. Here, using two previously described F-protein mutations (S443D or P22L), we examine the capacity to modulate PIV5 F stability and the mechanisms by which these point mutants act. The S443D mutation destabilizes prefusion F proteins by disrupting a hydrogen bond network at the base of the F-protein globular head. The introduction of a P22L mutation robustly rescues destabilized F proteins through a local hydrophobic interaction between the N-terminal helix and a hydrophobic pocket. Prefusion stabilization conferred by a P22L-homologous mutation is demonstrated in the F protein of Newcastle disease virus, a paramyxovirus of a different genus, suggesting a conserved stabilizing structural element within the paramyxovirus family. Taken together, the available data suggest that movement of the N-terminal helix is a necessary early step for paramyxovirus F-protein refolding and presents a novel target for structure-based drug design.
authors.affiliation: Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208-3500;
authors.forename: Albert S
authors.initials: AS
authors.lastname: Song
authors.affiliation: Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208-3500;
authors.forename: Taylor A
authors.initials: TA
authors.lastname: Poor
authors.affiliation: Institute of Bioengineering, School of Life Sciences, École Polytechnique Fédérale de Lausanne, CH-1050 Lausanne, Switzerland; Swiss Institute of Bioinformatics, CH-1015 Lausanne, Switzerland;
authors.forename: Luciano A
authors.initials: LA
authors.lastname: Abriata
authors.affiliation: Department of Structural Biology, Stanford University, Stanford, CA 94305;
authors.forename: Theodore S
authors.initials: TS
authors.lastname: Jardetzky
authors.affiliation: Institute of Bioengineering, School of Life Sciences, École Polytechnique Fédérale de Lausanne, CH-1050 Lausanne, Switzerland; Swiss Institute of Bioinformatics, CH-1015 Lausanne, Switzerland; matteo.dalperaro@epfl.ch ralamb@northwestern.edu.
authors.forename: Matteo
authors.initials: M
authors.lastname: Dal Peraro
authors.affiliation: Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208-3500; Howard Hughes Medical Institute, Northwestern University, Evanston, IL 60208-3500 matteo.dalperaro@epfl.ch ralamb@northwestern.edu.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Lamb
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D002522:Chlorocebus aethiops; D008968:Molecular Conformation; D009154:Mutation; D045402:Parainfluenza Virus 5 / Q000378:metabolism*; D055550:Protein Stability; D014709:Vero Cells; D014760:Viral Fusion Proteins / Q000378:metabolism*
chemical_list: D014760:Viral Fusion Proteins
keywords: molecular dynamics simulation; protein refolding; viral fusion protein