The Major Role of the Rab Ypt7p in Vacuole Fusion Is Supporting HOPS Membrane Association*♦
AUTOR(ES)
Hickey, Christopher M.
FONTE
American Society for Biochemistry and Molecular Biology
RESUMO
Yeast vacuole fusion requires soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs), the Rab GTPase Ypt7p, vacuolar lipids, Sec17p and Sec18p, and the homotypic fusion and vacuole protein sorting complex (HOPS). HOPS is a multisubunit protein with direct affinities for SNAREs, vacuolar lipids, and the GTP-bound form of Ypt7p; each of these affinities contributes to HOPS association with the organelle. Using all-purified components, we have reconstituted fusion, but the Rab Ypt7p was not required. We now report that phosphorylation of HOPS by the vacuolar kinase Yck3p blocks HOPS binding to vacuolar lipids, making HOPS membrane association and the ensuing fusion depend on the presence of Ypt7p. In accord with this finding in the reconstituted fusion reaction, the inactivation of Ypt7p by the GTPase-activating protein Gyp1–46p only blocks the fusion of purified vacuoles when Yck3p is present and active. Thus, although Ypt7p may contribute to other fusion functions, its central role is to bind HOPS to the membrane.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2713515Documentos Relacionados
- The GTPase Ypt7p of Saccharomyces cerevisiae is required on both partner vacuoles for the homotypic fusion step of vacuole inheritance.
- Rho1p and Cdc42p act after Ypt7p to regulate vacuole docking
- A Ypt/Rab effector complex containing the Sec1 homolog Vps33p is required for homotypic vacuole fusion
- The GTPase-Activating Enzyme Gyp1p Is Required for Recycling of Internalized Membrane Material by Inactivation of the Rab/Ypt GTPase Ypt1p
- Schizosaccharomyces pombe ypt5: a homologue of the rab5 endosome fusion regulator.