Brindley MA Plattet P Plemper RK 2014 Enveloped viruses such as HIV and members of the paramyxovirus family use metastable, proteinaceous fusion machineries to merge the viral envelope with cellular membranes for infection. A hallmark of the fusogenic glycoproteins of these pathogens is refolding into a thermodynamically highly stable fusion core structure composed of six antiparallel α-helices, and this structure is considered instrumental for pore opening and/or enlargement. Using a paramyxovirus fusion (F) protein, we tested this paradigm by engineering covalently restricted F proteins that are predicted to be unable to close the six-helix bundle core structure fully. Several candidate bonds formed efficiently, resulting in F trimers and higher-order complexes containing covalently linked dimers. The engineered F complexes were incorporated into recombinant virions efficiently and were capable of refolding into a postfusion conformation without temporary or permanent disruption of the disulfide bonds. They efficiently formed fusion pores based on virus replication and quantitative cell-to-cell and virus-to-cell fusion assays. Complementation of these F mutants with a monomeric, fusion-inactive F variant enriched the F oligomers for heterotrimers containing a single disulfide bond, without affecting fusion complementation profiles compared with standard F protein. Our demonstration that complete closure of the fusion core does not drive paramyxovirus entry may aid the design of strategies for inhibiting virus entry. application/pdf https://sonar.ch/global/documents/56484 eng info:eu-repo/semantics/altIdentifier/doi/10.1073/pnas.1403609111 info:eu-repo/semantics/altIdentifier/pmid/25157143 info:eu-repo/semantics/openAccess Proceedings of the National Academy of Sciences of the United States of America. - 2014 measles virus membrane fusion Amino Acid Sequence Animals COS Cells Chickens Chlorocebus aethiops Cysteine Disulfides Humans Kinetics Measles virus Models, Molecular Molecular Sequence Data Mutant Proteins Protein Engineering Protein Multimerization Protein Refolding Protein Stability Protein Structure, Secondary Protein Structure, Tertiary Recombination, Genetic Viral Fusion Proteins Virus Replication Efficient replication of a paramyxovirus independent of full zippering of the fusion protein six-helix bundle domain. http://purl.org/coar/resource_type/c_6501