The transmembrane domain of Vam3 affects the composition of cis- and trans-SNARE complexes to promote homotypic vacuole fusion.
It is presently not clear how the function of SNARE proteins is affected by their transmembrane domains. Here, we analyzed the role of the transmembrane domain of the vacuolar SNARE Vam3 by replacing it by a lipid anchor. Vacuoles with mutant Vam3 fuse poorly and have increased amounts of cis-SNARE complexes, indicating that they are more stable. As a consequence efficient cis-SNARE complex disassembly that occurs at priming as a prerequisite of fusion requires addition of exogenous Sec18. trans-SNARE complexes in this mutant accumulate up to 4-fold over wild type, suggesting that the transmembrane domain of Vam3 is required to transit through this step. Finally, palmitoylation of Vac8, a reaction that also occurs early during priming is reduced by almost one-half. Since palmitoylated Vac8 is required beyond trans-SNARE complex formation, this may partially explain the fusion deficiency.
Rohde
Jan
J
Interdisziplinäres Zentrum für Neurowissenschaften, University of Heidelberg, Im Neuenheimer Feld 307, 69120 Heidelberg, Germany.
Dietrich
Lars
L
Langosch
Dieter
D
Ungermann
Christian
C
D000595:Amino Acid Sequence; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D008561:Membrane Fusion; D008565:Membrane Proteins / Q000737:chemistry / Q000502:physiology*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D050765:Qa-SNARE Proteins; D050600:SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D014617:Vacuoles / Q000502:physiology*; D033921:Vesicular Transport Proteins
D005656:Fungal Proteins; D008565:Membrane Proteins; D050765:Qa-SNARE Proteins; D050600:SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins; C107706:VAM3 protein, S cerevisiae; D033921:Vesicular Transport Proteins