title: Sec1/Munc18 protein stabilizes fusion-competent syntaxin for membrane fusion in Arabidopsis cytokinesis.
abstract: Intracellular membrane fusion requires complexes of syntaxins with other SNARE proteins and regulatory Sec1/Munc18 (SM) proteins. In membrane fusion mediating, e.g., neurotransmitter release or glucose-stimulated insulin secretion in mammals, SM proteins preferentially interact with the inactive closed, rather than the active open, conformation of syntaxin or with the assembled SNARE complex. Other membrane fusion processes such as vacuolar fusion in yeast involve like membranes carrying cis-SNARE complexes, and the role of SM protein is unknown. We investigated syntaxin-SM protein interaction in membrane fusion of Arabidopsis cytokinesis, which involves cytokinesis-specific syntaxin KNOLLE and SM protein KEULE. KEULE interacted with an open conformation of KNOLLE that complemented both knolle and keule mutants. This interaction occurred at the cell division plane and required the KNOLLE linker sequence between helix Hc and SNARE domain. Our results suggest that in cytokinesis, SM protein stabilizes the fusion-competent open form of syntaxin, thereby promoting trans-SNARE complex formation.
authors.affiliation: Zentrum für Molekularbiologie der Pflanzen, Entwicklungsgenetik, University of Tübingen, Auf der Morgenstelle 3, 72076 Tübingen, Germany.
authors.forename: Misoon
authors.initials: M
authors.lastname: Park
authors.forename: Sonja
authors.initials: S
authors.lastname: Touihri
authors.forename: Isabel
authors.initials: I
authors.lastname: Müller
authors.forename: Ulrike
authors.initials: U
authors.lastname: Mayer
authors.forename: Gerd
authors.initials: G
authors.lastname: Jürgens
mesh_terms: D017360:Arabidopsis / Q000166:cytology* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D018797:Cell Cycle Proteins; D048749:Cytokinesis / Q000502:physiology*; D007425:Intracellular Membranes / Q000378:metabolism; D008561:Membrane Fusion / Q000502:physiology*; D018613:Microscopy, Confocal; D051938:Munc18 Proteins / Q000378:metabolism*; D050505:Mutant Proteins / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D050765:Qa-SNARE Proteins / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D014617:Vacuoles
chemical_list: C426230:AT1G12360 protein, Arabidopsis; D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; C097724:KNOLLE protein, Arabidopsis; D051938:Munc18 Proteins; D050505:Mutant Proteins; D050765:Qa-SNARE Proteins