A novel SNARE complex implicated in vesicle fusion with the endoplasmic reticulum.
Intracellular vesicular traffic is controlled in part by v- and t-SNAREs, integral membrane proteins which allow specific interaction and fusion between vesicles (v-SNAREs) and their target membranes (t-SNAREs). In yeast, retrograde transport from the Golgi complex to the ER is mediated by the ER t-SNARE Ufe1p, and also requires two other ER proteins, Sec20p and Tip20p, which bind each other. Although Sec20p is not a typical SNARE, we show that both it and Tip20p can be co-precipitated with Ufe1p, and that a growth-inhibiting mutation in Ufe1p can be compensated by a mutation in Sec20p. Furthermore, Sec22p, a v-SNARE implicated in forward transport from ER to Golgi, co-precipitates with Ufe1p and Sec20p, and SEC22 acts as an allele-specific multicopy suppressor of a temperature-sensitive ufe1 mutation. These results define a new functional SNARE complex, with features distinct from the plasma membrane and cis-Golgi complexes previously identified. They also show that a single v-SNARE can be involved in both anterograde and retrograde transport, which suggests that the mere presence of a particular v-SNARE may not be sufficient to determine the preferred target for a transport vesicle.
Lewis
M J
MJ
MRC Laboratory of Molecular Biology, Cambridge, UK.
Rayner
J C
JC
Pelham
H R
HR
D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000378:metabolism*; D002451:Cell Compartmentation; D004721:Endoplasmic Reticulum / Q000502:physiology*; D005656:Fungal Proteins / Q000378:metabolism; D018628:Gene Dosage; D006023:Glycoproteins; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D046911:Macromolecular Substances; D008561:Membrane Fusion / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D011233:Precipitin Tests; D011485:Protein Binding; D050765:Qa-SNARE Proteins; D050766:Qb-SNARE Proteins; D050683:R-SNARE Proteins; D011956:Receptors, Cell Surface / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D013489:Suppression, Genetic; D033921:Vesicular Transport Proteins; D015003:Yeasts / Q000502:physiology
D002352:Carrier Proteins; D005656:Fungal Proteins; D006023:Glycoproteins; D018840:HSP70 Heat-Shock Proteins; C060153:KAR2 protein, yeast; D046911:Macromolecular Substances; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D050765:Qa-SNARE Proteins; D050766:Qb-SNARE Proteins; D050683:R-SNARE Proteins; D011956:Receptors, Cell Surface; C073173:SEC20 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C106909:Sec22 protein, S cerevisiae; C489479:TIP20 protein, S cerevisiae; C103868:UFE1 protein, S cerevisiae; D033921:Vesicular Transport Proteins