A ras-like protein is required for a post-Golgi event in yeast secretion

Cell. 1987 May 22;49(4):527-38. doi: 10.1016/0092-8674(87)90455-7.


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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Cloning, Molecular
  • Fungal Proteins / physiology*
  • Genes*
  • Genes, Fungal*
  • Golgi Apparatus / ultrastructure*
  • Microscopy, Electron
  • Mutation
  • Oncogenes*
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae / physiology
  • Saccharomyces cerevisiae / ultrastructure
  • Sequence Homology, Nucleic Acid
  • Species Specificity
  • ras Proteins*


  • Fungal Proteins
  • ras Proteins

Associated data

  • GENBANK/M16507