title: Mechanical unzipping and rezipping of a single SNARE complex reveals hysteresis as a force-generating mechanism.
abstract: Formation of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex provides mechanical thrust for membrane fusion, but its molecular mechanism is still unclear. Here using magnetic tweezers, we observe mechanical responses of a single neuronal SNARE complex under constant pulling force. Single SNARE complexes may be unzipped with 34 pN force. When rezipping is induced by lowering the force to 11 pN, only a partially assembled state results, with the C-terminal half of the SNARE complex remaining disassembled. Reassembly of the C-terminal half occurs only when the force is further lowered below 11 pN. Thus, mechanical hysteresis, characterized by the unzipping and rezipping cycle of a single SNARE complex, produces the partially assembled state. In this metastable state, unzipping toward the N-terminus is suppressed while zippering toward the C-terminus is initiated as a steep function of force. This ensures the directionality of SNARE-complex formation, making the SNARE complex a robust force-generating machine.
authors.affiliation: National Creative Research Initiative Center for Single-Molecule Systems Biology, KAIST, Daejeon 305-701, South Korea.
authors.forename: Duyoung
authors.initials: D
authors.lastname: Min
authors.forename: Kipom
authors.initials: K
authors.lastname: Kim
authors.forename: Changbong
authors.initials: C
authors.lastname: Hyeon
authors.forename: Yong Hoon
authors.initials: YH
authors.lastname: Cho
authors.forename: Yeon-Kyun
authors.initials: YK
authors.lastname: Shin
authors.forename: Tae-Young
authors.initials: TY
authors.lastname: Yoon
mesh_terms: D008280:Magnetics; D008561:Membrane Fusion; D050600:SNARE Proteins / Q000378:metabolism*
chemical_list: D050600:SNARE Proteins