title: Yeast Vps45p is a Sec1p-like protein required for the consumption of vacuole-targeted, post-Golgi transport vesicles.
abstract: Over 45 VPS genes (vacuolar protein sorting) in Saccharomyces cerevisiae are necessary for the correct sorting and delivery of vacuolar hydrolases. Yeast strains carrying mutations in a subset of these VPS genes (class D vps mutants) are also defective in the segregation of vacuolar material into the developing daughter cell and are morphologically characterized by having large central vacuoles. The class D VPS gene products, which include a Rab5 homologue (VPS21/YPT51) and a syntaxin homologue (PEP12/VPS6), have been proposed to function together at a particular step along the vacuolar protein sorting pathway. We have cloned another class D VPS gene, VPS45, which is homologous to a growing family of genes that encode Sec1p-like proteins. Vps45p is predicted to be a hydrophilic protein of 577 amino acids with a molecular mass of 67 kDa. Fractionation studies show that Vps45p is a peripheral membrane protein that cofractionates with Golgi-like membranes, consistent with Vps45p functioning in membrane traffic between the Golgi and the vacuole. Using a temperature-sensitive allele of VPS45, we show that inactivation of Vps45p causes the rapid accumulation of small (40-60 nm) vesicles and secretion of the vacuolar hydrolase carboxypeptidase Y. Because the entire yeast secretory pathway is functional after the temperature-induced inactivation of Vps45p, we conclude that the accumulated vesicles represent transport intermediates between the Golgi and the vacuole.
authors.affiliation: Institute of Molecular Biology, University of Oregon, Eugene 97403-1229.
authors.forename: R C
authors.initials: RC
authors.lastname: Piper
authors.forename: E A
authors.initials: EA
authors.lastname: Whitters
authors.forename: T H
authors.initials: TH
authors.lastname: Stevens
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001692:Biological Transport / Q000502:physiology; D003001:Cloning, Molecular; D005656:Fungal Proteins / Q000235:genetics*; D006056:Golgi Apparatus / Q000378:metabolism*; D008081:Liposomes; D008565:Membrane Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D005810:Multigene Family; D051938:Munc18 Proteins; D009419:Nerve Tissue Proteins; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013696:Temperature; D014617:Vacuoles / Q000378:metabolism*; D033921:Vesicular Transport Proteins
chemical_list: D005656:Fungal Proteins; D008081:Liposomes; D008565:Membrane Proteins; D051938:Munc18 Proteins; D009419:Nerve Tissue Proteins; D029701:Saccharomyces cerevisiae Proteins; C092934:VPS45 protein, S cerevisiae; D033921:Vesicular Transport Proteins