Abstract
The COPII coat buds transport vesicles from the endoplasmic reticulum that incorporate cargo and SNARE molecules. Here, we show that recognition of the ER-Golgi SNAREs Bet1, Sed5, and Sec22 occurs through three binding sites on the Sec23/24 subcomplex of yeast COPII. The A site binds to the YNNSNPF motif of Sed5. The B site binds to Lxx-L/M-E sequences present in both the Bet1 and Sed5 molecules, as well as to the DxE cargo-sorting signal. A third, spatially distinct site binds to Sec22. COPII selects the free v-SNARE form of Bet1 because the LxxLE sequence is sequestered in the four-helix bundle of the v-/t-SNARE complex. COPII favors Sed5 within the Sed5/Bos1/Sec22 t-SNARE complex because t-SNARE assembly removes autoinhibitory contacts to expose the YNNSNPF motif. The COPII coat seems to be a specific conductor of the fusogenic forms of these SNAREs, suggesting how vesicle fusion specificity may be programmed during budding.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Motifs
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COP-Coated Vesicles / metabolism*
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Carrier Proteins / genetics
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Carrier Proteins / metabolism*
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Crystallography, X-Ray
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GTPase-Activating Proteins
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Macromolecular Substances
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Membrane Proteins / genetics
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Membrane Proteins / metabolism*
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Membrane Transport Proteins / genetics
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Membrane Transport Proteins / metabolism
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Models, Molecular
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Phosphoproteins / genetics
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Phosphoproteins / metabolism*
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Protein Binding
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Protein Structure, Tertiary
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Protein Transport / physiology
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Qa-SNARE Proteins
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Qc-SNARE Proteins
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R-SNARE Proteins
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Receptors, Cell Surface / genetics
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Receptors, Cell Surface / metabolism
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SNARE Proteins
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Saccharomyces cerevisiae Proteins / genetics
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Saccharomyces cerevisiae Proteins / metabolism
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Substrate Specificity
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Vesicular Transport Proteins*
Substances
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BET1 protein, S cerevisiae
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Carrier Proteins
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GTPase-Activating Proteins
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Macromolecular Substances
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Membrane Proteins
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Membrane Transport Proteins
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Phosphoproteins
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Qa-SNARE Proteins
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Qc-SNARE Proteins
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R-SNARE Proteins
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Receptors, Cell Surface
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SEC23 protein, S cerevisiae
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SEC31 protein, S cerevisiae
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SNARE Proteins
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Saccharomyces cerevisiae Proteins
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Sec22 protein, S cerevisiae
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Sed5 protein, S cerevisiae
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Vesicular Transport Proteins
Associated data
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PDB/1PCX
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PDB/1PD0
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PDB/1PD1