title: The SM protein Vps33 and the t-SNARE H(abc) domain promote fusion pore opening.
abstract: Intracellular membrane fusion proceeds via distinct stages of membrane docking, hemifusion and fusion pore opening and depends on interacting families of Rab, SNARE and SM proteins. Trans-SNARE complexes dock the membranes in close apposition. Efficient fusion requires further SNARE-associated proteins. They might increase the number of trans-SNARE complexes or the fusogenic potential of a single SNARE complex. We investigated the contributions of the SM protein Vps33 to hemifusion and pore opening between yeast vacuoles. Mutations in Vps33 that weaken its interactions with the SNARE complex allowed normal trans-SNARE pairing and lipid mixing but retarded content mixing. Deleting the H(abc) domain of the vacuolar t-SNARE Vam3, which interacts with Vps33, had the same effect. This suggests that SM proteins promote fusion pore opening by enhancing the fusogenic activity of a SNARE complex. They should thus be considered integral parts of the fusion machinery.
authors.affiliation: Département de Biochimie, Université de Lausanne, Epalinges, Switzerland.
authors.forename: Michel
authors.initials: M
authors.lastname: Pieren
authors.forename: Andrea
authors.initials: A
authors.lastname: Schmidt
authors.forename: Andreas
authors.initials: A
authors.lastname: Mayer
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D008561:Membrane Fusion / Q000235:genetics / Q000502:physiology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes; D009154:Mutation; D054730:Protein Interaction Domains and Motifs; D050765:Qa-SNARE Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D050600:SNARE Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014617:Vacuoles / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D046912:Multiprotein Complexes; D050765:Qa-SNARE Proteins; D011994:Recombinant Proteins; D050600:SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins; C107706:VAM3 protein, S cerevisiae; C065454:VPS33 protein, S cerevisiae; D033921:Vesicular Transport Proteins
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