Abstract
Yeast vacuoles undergo priming, docking, and homotypic fusion, although little has been known of the connections between these reactions. Vacuole-associated Vam2p and Vam6p (Vam2/6p) are components of a 65S complex containing SNARE proteins. Upon priming by Sec18p/NSF and ATP, Vam2/6p is released as a 38S subcomplex that binds Ypt7p to initiate docking. We now report that the 38S complex consists of both Vam2/6p and the class C Vps proteins [Reider, S. E. and Emr, S. D. (1997) Mol. Biol. Cell 8, 2307-2327]. This complex includes Vps33p, a member of the Sec1 family of proteins that bind t-SNAREs. We term this 38S complex HOPS, for homotypic fusion and vacuole protein sorting. This unexpected finding explains how Vam2/6p associates with SNAREs and provides a mechanistic link of the class C Vps proteins to Ypt/Rab action. HOPS initially associates with vacuole SNAREs in "cis" and, after release by priming, hops to Ypt7p, activating this Ypt/Rab switch to initiate docking.
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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Adaptor Proteins, Vesicular Transport
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Antibodies / pharmacology
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Carrier Proteins / classification
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Carrier Proteins / metabolism
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Centrifugation, Density Gradient
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Fungal Proteins / classification
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Fungal Proteins / metabolism*
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Macromolecular Substances
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Membrane Fusion* / drug effects
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Membrane Proteins / classification
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Membrane Proteins / metabolism
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Nuclear Proteins*
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Precipitin Tests
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Protein Binding
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RNA-Binding Proteins / classification
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RNA-Binding Proteins / metabolism
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Recombinant Fusion Proteins / chemistry
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Recombinant Fusion Proteins / metabolism
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SNARE Proteins
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Saccharomyces cerevisiae / cytology*
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Saccharomyces cerevisiae / drug effects
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae / metabolism*
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Saccharomyces cerevisiae Proteins*
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Vacuoles / chemistry
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Vacuoles / drug effects
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Vacuoles / metabolism*
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Vesicular Transport Proteins*
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rab GTP-Binding Proteins / genetics
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rab GTP-Binding Proteins / metabolism*
Substances
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Adaptor Proteins, Vesicular Transport
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Antibodies
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Carrier Proteins
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Fungal Proteins
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Macromolecular Substances
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Membrane Proteins
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NPL3 protein, S cerevisiae
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Nuclear Proteins
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RNA-Binding Proteins
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Recombinant Fusion Proteins
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SNARE Proteins
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Saccharomyces cerevisiae Proteins
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VAM6 protein, S cerevisiae
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VPS33 protein, S cerevisiae
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VPS41 protein, S cerevisiae
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Vesicular Transport Proteins
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YPT7 protein, S cerevisiae
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rab GTP-Binding Proteins