SNARE selectivity of the COPII coat.

Howard Hughes Medical Institute and the Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10021, USA.
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.
Mesh Terms:
Amino Acid Motifs, COP-Coated Vesicles, Carrier Proteins, Crystallography, X-Ray, GTPase-Activating Proteins, Macromolecular Substances, Membrane Proteins, Membrane Transport Proteins, Models, Molecular, Phosphoproteins, Protein Binding, Protein Structure, Tertiary, Protein Transport, Qa-SNARE Proteins, Qc-SNARE Proteins, R-SNARE Proteins, Receptors, Cell Surface, SNARE Proteins, Saccharomyces cerevisiae Proteins, Substrate Specificity, Vesicular Transport Proteins
Cell Aug. 22, 2003; 114(4);483-95 [PUBMED:12941276]
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