An effector of Ypt6p binds the SNARE Tlg1p and mediates selective fusion of vesicles with late Golgi membranes.
Membrane traffic requires vesicles to fuse with a specific target, and SNARE proteins and Rab/Ypt GTPases contribute to this specificity. In the yeast Saccharomyces cerevisae, the Rab/Ypt GTPase Ypt6p is required for fusion of endosome-derived vesicles with the late Golgi. We have shown previously that activation of Ypt6p depends on its exchange factor, Ric1p-Rgp1p, a peripheral membrane protein complex restricted to the Golgi. We show here that a conserved trimeric protein complex, VFT (Vps52/53/54), binds directly to Ypt6p:GTP. Localization of VFT to the Golgi requires Ypt6p, but is unaffected in gos1 and tlg1 mutants, in which late Golgi integral membrane proteins, including SNAREs, are mislocalized. The VFT complex also binds directly to the N-terminal domain of the SNARE Tlg1p, both in vitro and in vivo, in a Ypt6p-independent manner. We suggest that the VFT complex links vesicles containing Tlg1p to their target, which is defined by the local activation of Ypt6p.
Siniossoglou
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MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK.
Pelham
H R
HR
D022162:Cytoplasmic Vesicles / Q000378:metabolism*; D011992:Endosomes / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism*; D007425:Intracellular Membranes / Q000378:metabolism*; D046911:Macromolecular Substances; D008561:Membrane Fusion / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism*; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D050600:SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D033921:Vesicular Transport Proteins
D005656:Fungal Proteins; D046911:Macromolecular Substances; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; D050600:SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins; C093602:VPS52 protein, S cerevisiae; C117606:VPS54 protein, S cerevisiae; D033921:Vesicular Transport Proteins; D020559:Monomeric GTP-Binding Proteins