Abstract
Vacuole fusion requires Sec18p (NSF), Sec17p (alpha-SNAP), Ypt7p (GTP binding protein), Vam3p (t-SNARE), Nyv1p (v-SNARE), and LMA1 (low Mr activity 1, a heterodimer of thioredoxin and I(B)2). LMA1 requires Sec18p for saturable, high-affinity binding to vacuoles, and Sec18p "priming" ATPase requires both Sec17p and LMA1. Either the sec18-1 mutation and deletion of I(B)2, or deletion of both I(B)2 and p13 (an I(B)2 homolog) causes a striking synthetic vacuole fragmentation phenotype. Upon Sec18p ATP hydrolysis, LMA1 transfers to (and stabilizes) a Vam3p complex. LMA1 is released from vacuoles in a phosphatase-regulated reaction. This LMA1 cycle explains how priming by Sec18p is coupled to t-SNARE stabilization and to fusion.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adenosine Triphosphatases*
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Adenosine Triphosphate / metabolism
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Amino Acid Sequence
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Enzyme Inhibitors / pharmacology
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Fungal Proteins / genetics
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Fungal Proteins / metabolism*
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Glycoproteins / genetics
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Glycoproteins / metabolism*
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Hydrolysis
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Marine Toxins
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Membrane Fusion / physiology*
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Membrane Proteins*
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Microcystins
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Molecular Sequence Data
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Mutation
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Peptides, Cyclic / pharmacology
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Phosphoprotein Phosphatases / antagonists & inhibitors
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Phosphoproteins
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Protein Binding
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Qa-SNARE Proteins
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Saccharomyces cerevisiae / cytology
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Saccharomyces cerevisiae Proteins*
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Thioredoxins / metabolism*
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Vacuoles / metabolism*
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Vesicular Transport Proteins*
Substances
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Enzyme Inhibitors
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Fungal Proteins
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Glycoproteins
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Marine Toxins
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Membrane Proteins
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Microcystins
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Peptides, Cyclic
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Phosphoproteins
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Qa-SNARE Proteins
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Saccharomyces cerevisiae Proteins
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VAM3 protein, S cerevisiae
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Vesicular Transport Proteins
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yeast proteinase B inhibitor
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Thioredoxins
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Adenosine Triphosphate
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Phosphoprotein Phosphatases
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Adenosine Triphosphatases
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SEC18 protein, S cerevisiae
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cyanoginosin LR