title: Multiple intermediates in SNARE-induced membrane fusion.
abstract: Membrane fusion in eukaryotic cells is thought to be mediated by a highly conserved family of proteins called SNAREs (soluble N-ethyl maleimide sensitive-factor attachment protein receptors). The vesicle-associated v-SNARE engages with its partner t-SNAREs on the target membrane to form a coiled coil that bridges two membranes and facilitates fusion. As demonstrated by recent findings on the hemifusion state, identifying intermediates of membrane fusion can help unveil the underlying fusion mechanism. Observation of SNARE-driven fusion at the single-liposome level has the potential to dissect and characterize fusion intermediates most directly. Here, we report on the real-time observation of lipid-mixing dynamics in a single fusion event between a pair of SNARE-reconstituted liposomes. The assay reveals multiple intermediate states characterized by discrete values of FRET between membrane-bound fluorophores. Hemifusion, flickering of fusion pores, and kinetic transitions between intermediates, which would be very difficult to detect in ensemble assays, are now identified. The ability to monitor the time course of fusion events between two proteoliposomes should be useful for addressing many important issues in SNARE-mediated membrane fusion.
authors.affiliation: Howard Hughes Medical Institute, Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Tae-Young
authors.initials: TY
authors.lastname: Yoon
authors.forename: Burak
authors.initials: B
authors.lastname: Okumus
authors.forename: Fan
authors.initials: F
authors.lastname: Zhang
authors.forename: Yeon-Kyun
authors.initials: YK
authors.lastname: Shin
authors.forename: Taekjip
authors.initials: T
authors.lastname: Ha
mesh_terms: D031541:Fluorescence Resonance Energy Transfer; D007700:Kinetics; D008081:Liposomes; D008854:Microscopy, Electron; D050600:SNARE Proteins / Q000737:chemistry* / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000378:metabolism; D013997:Time Factors
chemical_list: D008081:Liposomes; D050600:SNARE Proteins