A ras-like protein is required for a post-Golgi event in yeast secretion.
Secretion is blocked at the post-Golgi stage within 5 min of a shift of sec4-8 cells from 25 degrees C to 37 degrees C. Analysis of SEC4 predicts a protein product of 23.5 kd molecular weight that shares 32% homology with ras proteins and is essential for growth. The regions of best homology are those involved in the binding and hydrolysis of GTP. Duplication of SEC4 suppresses post-Golgi-blocked mutations in three sec genes. These mutations are lethal when combined with sec4-8 at 25 degrees C. Mutations that block elsewhere on the pathway are not suppressed by the SEC4 duplication and are not lethal when combined with sec4-8. We propose that the SEC4 product is a GTP-binding protein that plays an essential role in controlling a late stage of the secretory pathway.
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D005656:Fungal Proteins / Q000502:physiology*; D005796:Genes; D005800:Genes, Fungal; D006056:Golgi Apparatus / Q000648:ultrastructure*; D008854:Microscopy, Electron; D009154:Mutation; D009857:Oncogenes; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000502:physiology / Q000648:ultrastructure; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity; D018631:ras Proteins
D005656:Fungal Proteins; D018631:ras Proteins