title: The Sec1/Munc18 Protein Groove Plays a Conserved Role in Interaction with Sec9p/SNAP-25.
abstract: The Sec1/Munc18 (SM) proteins constitute a conserved family with essential functions in SNARE-mediated membrane fusion. Recently, a new protein-protein interaction site in Sec1p, designated the groove, was proposed. Here, we show that a sec1 groove mutant yeast strain, sec1(w24), displays temperature-sensitive growth and secretion defects. The yeast Sec1p and mammalian Munc18-1 grooves were shown to play an important role in the interaction with the SNAREs Sec9p and SNAP-25b, respectively. Incubation of SNAP-25b with the Munc18-1 groove mutant resulted in a lag in the kinetics of SNARE complex assembly in vitro when compared with wild-type Munc18-1. The SNARE regulator SRO7 was identified as a multicopy suppressor of sec1(w24) groove mutant and an intact Sec1p groove was required for the plasma membrane targeting of Sro7p-SNARE complexes. Simultaneous inactivation of Sec1p groove and SRO7 resulted in reduced levels of exocytic SNARE complexes. Our results identify the groove as a conserved interaction surface in SM proteins. The results indicate that this structural element is important for interactions with Sec9p/SNAP-25 and participates, in concert with Sro7p, in the initial steps of SNARE complex assembly.
authors.affiliation: Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, P.O. Box 56, FI-00014, Helsinki, Finland.|Minerva Foundation Institute for Medical Research, Tukholmankatu 8, FI-00290, Helsinki, Finland.
authors.forename: Marion
authors.initials: M
authors.lastname: Weber-Boyvat
authors.affiliation: Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, P.O. Box 56, FI-00014, Helsinki, Finland.
authors.forename: Konstantin G
authors.initials: KG
authors.lastname: Chernov
authors.affiliation: Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, P.O. Box 56, FI-00014, Helsinki, Finland.|VTT Technical Research Centre of Finland, Tietotie 2, FIN 02044 VTT, Espoo, Finland.
authors.forename: Nina
authors.initials: N
authors.lastname: Aro
authors.affiliation: Computer-Aided Drug Design, Orion Pharma, P.O. Box 65, 02101, Espoo, Finland.
authors.forename: Gerd
authors.initials: G
authors.lastname: Wohlfahrt
authors.affiliation: Minerva Foundation Institute for Medical Research, Tukholmankatu 8, FI-00290, Helsinki, Finland.
authors.forename: Vesa M
authors.initials: VM
authors.lastname: Olkkonen
authors.affiliation: Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, P.O. Box 56, FI-00014, Helsinki, Finland.|VTT Technical Research Centre of Finland, Tietotie 2, FIN 02044 VTT, Espoo, Finland.
authors.forename: Jussi
authors.initials: J
authors.lastname: Jäntti
mesh_terms: D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008561:Membrane Fusion / Q000502:physiology; D051938:Munc18 Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D011485:Protein Binding / Q000502:physiology; D050825:Synaptosomal-Associated Protein 25 / Q000235:genetics / Q000378:metabolism*; D015003:Yeasts / Q000235:genetics / Q000378:metabolism
chemical_list: D005656:Fungal Proteins; D051938:Munc18 Proteins; D050825:Synaptosomal-Associated Protein 25
keywords: Munc18; SNAP-25; SNARE; Sec1; Sec9; Sro7; Tomosyn; exocytosis