title: The Sec1p/Munc18 (SM) protein, Vps45p, cycles on and off membranes during vesicle transport.
abstract: Protein phosphatase 1 (PP1, Glc7p) functions in the final stage of SNARE-mediated vesicle transport between docking and fusion. During this process, trans-SNARE complexes, formed between molecules in opposing membranes, convert to cis-complexes, with all participants in the same lipid bilayer. Here, we show that glc7 mutant cells accumulate SNARE complexes. These complexes are clearly different from those found in either wild-type or sec18-1 cells as the Sec1p/Munc18 (SM) protein Vps45p does not bind to them. Given that PP1 controls fusion, the SNARE complexes that accumulate in glc7 mutants likely represent trans-SNARE complexes. Vps45p dissociates from the membrane in the absence of PP1 activity, but rapidly reassociates after its reactivation. These data reveal that SM proteins cycle on and off membranes in a stage-specific manner during the vesicle transport reaction, and suggest that protein phosphorylation plays a key role in the regulation of this cycle.
authors.affiliation: The Garvan Institute of Medical Research, Darlinghurst, Sydney, NSW, Australia 2010. n.bryant@bio.gla.ac.uk
authors.forename: Nia J
authors.initials: NJ
authors.lastname: Bryant
authors.forename: David E
authors.initials: DE
authors.lastname: James
mesh_terms: D001693:Biological Transport, Active; D007425:Intracellular Membranes / Q000378:metabolism*; D046911:Macromolecular Substances; D008561:Membrane Fusion; D008565:Membrane Proteins / Q000378:metabolism; D026901:Membrane Transport Proteins; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D054645:Protein Phosphatase 1; D050765:Qa-SNARE Proteins; D050600:SNARE Proteins; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D022161:Transport Vesicles / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000378:metabolism*
chemical_list: D046911:Macromolecular Substances; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D050765:Qa-SNARE Proteins; D050600:SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins; C112252:TLG2 protein, S cerevisiae; C092934:VPS45 protein, S cerevisiae; D033921:Vesicular Transport Proteins; C092048:GLC7 protein, S cerevisiae; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1