SNARE selectivity of the COPII coat.
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.
Pubmed ID: 12941276 RIS Download
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