title: Kinetically coupled folding of a single HIV-1 glycoprotein 41 complex in viral membrane fusion and inhibition.
abstract: HIV-1 glycoprotein 41 (gp41) mediates viral entry into host cells by coupling its folding energy to membrane fusion. Gp41 folding is blocked by fusion inhibitors, including the commercial drug T20, to treat HIV/AIDS. However, gp41 folding intermediates, energy, and kinetics are poorly understood. Here, we identified the folding intermediates of a single gp41 trimer-of-hairpins and measured their associated energy and kinetics using high-resolution optical tweezers. We found that folding of gp41 hairpins was energetically independent but kinetically coupled: Each hairpin contributed a folding energy of ∼-23 kBT, but folding of one hairpin successively accelerated the folding rate of the next one by ∼20-fold. Membrane-mimicking micelles slowed down gp41 folding and reduced the stability of the six-helix bundle. However, the stability was restored by cooperative folding of the membrane-proximal external region. Surprisingly, T20 strongly inhibited gp41 folding by actively displacing the C-terminal hairpin strand in a force-dependent manner. The inhibition was abolished by a T20-resistant gp41 mutation. The energetics and kinetics of gp41 folding established by us provides a basis to understand viral membrane fusion, infection, and therapeutic intervention.
authors.affiliation: Department of Cell Biology, Yale University, School of Medicine, New Haven, CT 06511; Integrated Graduate Program in Physical and Engineering Biology, Yale University, New Haven, CT 06511;
authors.forename: Junyi
authors.initials: J
authors.lastname: Jiao
authors.affiliation: Department of Cell Biology, Yale University, School of Medicine, New Haven, CT 06511; Integrated Graduate Program in Physical and Engineering Biology, Yale University, New Haven, CT 06511; Department of Physics, Yale University, New Haven, CT 06511;
authors.forename: Aleksander A
authors.initials: AA
authors.lastname: Rebane
authors.affiliation: Department of Cell Biology, Yale University, School of Medicine, New Haven, CT 06511;
authors.forename: Lu
authors.initials: L
authors.lastname: Ma
authors.affiliation: Department of Cell Biology, Yale University, School of Medicine, New Haven, CT 06511; National Center for Protein Science Shanghai, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 201210, China;
authors.forename: Ying
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Department of Cell Biology, Yale University, School of Medicine, New Haven, CT 06511; Nanobiology Institute, Yale University, West Haven, CT 06477 yongli.zhang@yale.edu.
authors.forename: Yongli
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D000465:Algorithms; D000595:Amino Acid Sequence; D019380:Anti-HIV Agents / Q000494:pharmacology; D003001:Cloning, Molecular; D000077560:Enfuvirtide; D015700:HIV Envelope Protein gp41 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D015497:HIV-1 / Q000378:metabolism*; D007700:Kinetics; D016013:Likelihood Functions; D008958:Models, Molecular; D008969:Molecular Sequence Data; D052898:Optical Tweezers; D010446:Peptide Fragments; D017510:Protein Folding / Q000187:drug effects; D053586:Virus Internalization
chemical_list: D019380:Anti-HIV Agents; D015700:HIV Envelope Protein gp41; D010446:Peptide Fragments; D000077560:Enfuvirtide
keywords: fusion inhibitor; gp41 complex; optical tweezers; protein folding; viral fusion