[HTML][HTML] SNARE selectivity of the COPII coat

E Mossessova, LC Bickford, J Goldberg - Cell, 2003 - cell.com
E Mossessova, LC Bickford, J Goldberg
Cell, 2003cell.com
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/ME
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 …
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.
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