title: A GTP-binding protein required for secretion rapidly associates with secretory vesicles and the plasma membrane in yeast.
abstract: SEC4, one of the 10 genes involved in the final stage of the yeast secretory pathway, encodes a ras-like, GTP-binding protein. In wild-type cells, Sec4 protein is located on the cytoplasmic face of both the plasma membrane and the secretory vesicles in transit to the cell surface. In all post-Golgi blocked sec mutants, Sec4p is predominantly associated with the secretory vesicles that accumulate as a result of the secretory block. Sec4p is synthesized as a soluble protein that rapidly (t1/2 less than or equal to 1 min) and tightly associates with secretory vesicles and the plasma membrane by virtue of a conformational change of a covalent modification. These data suggest that Sec4p may function as a "G" protein on the vesicle surface to transduce an intracellular signal needed to regulate transport between the Golgi apparatus and the plasma membrane.
mesh_terms: D002462:Cell Membrane / Q000378:metabolism; D003594:Cytoplasmic Granules / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005796:Genes; D005800:Genes, Fungal; D005838:Genotype; D007700:Kinetics; D009154:Mutation; D010957:Plasmids; D011401:Promoter Regions, Genetic; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*
chemical_list: D019204:GTP-Binding Proteins