title: Genetic interactions with the yeast Q-SNARE VTI1 reveal novel functions for the R-SNARE YKT6.
abstract: SNARE proteins are required for fusion of transport vesicles with target membranes. Previously, we found that the yeast Q-SNARE Vti1p is involved in transport to the cis-Golgi, to the prevacuole/late endosome, and to the vacuole. Here we identified a previously uncharacterized gene, VTS1, and the R-SNARE YKT6 both as multicopy and as low copy suppressors of the growth and vacuolar transport defect in vti1-2 cells. Ykt6p was known to function in retrograde traffic to the cis-Golgi and homotypic vacuolar fusion. We found that VTI1 and YKT6 also interacted in traffic to the prevacuole and vacuole, indicating that these SNARE complexes contain Ykt6p, Vti1p, plus Pep12p and Ykt6p, Vti1p, Vam3p, plus Vam7p, respectively. As Ykt6p was required for several transport steps, R-SNAREs cannot be the sole determinants of specificity. To study the role of the 0 layer in the SNARE motif, we introduced the mutations vti1-Q158R and ykt6-R165Q. SNARE complexes to which Ykt6p contributed a fourth glutamine residue in the 0 layer were nonfunctional, suggesting an essential function for arginine in the 0 layer of these complexes. vti1-Q158R cells had severe defects in several transport steps, indicating that the second arginine in the 0 layer interfered with function.
authors.affiliation: Zentrum Biochemie und Molekulare Zellbiologie, Abteilung Biochemie II, Universität Göttingen, 37073 Göttingen, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Dilcher
authors.forename: B
authors.initials: B
authors.lastname: Köhler
authors.forename: G F
authors.initials: GF
authors.lastname: von Mollard
mesh_terms: D020816:Amino Acid Motifs; D002352:Carrier Proteins / Q000235:genetics* / Q000502:physiology; D005656:Fungal Proteins / Q000502:physiology*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology*; D050766:Qb-SNARE Proteins; D050683:R-SNARE Proteins; D050600:SNARE Proteins; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D013329:Structure-Activity Relationship; D033921:Vesicular Transport Proteins
chemical_list: D002352:Carrier Proteins; D005656:Fungal Proteins; D008565:Membrane Proteins; D050766:Qb-SNARE Proteins; D050683:R-SNARE Proteins; D050600:SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins; C106736:VTI1 protein, S cerevisiae; D033921:Vesicular Transport Proteins; C107127:YKT6 protein, S cerevisiae