Mso1p: a yeast protein that functions in secretion and interacts physically and genetically with Sec1p

Proc Natl Acad Sci U S A. 1997 Jul 8;94(14):7331-6. doi: 10.1073/pnas.94.14.7331.


The yeast Sec1p protein functions in the docking of secretory transport vesicles to the plasma membrane. We previously have cloned two yeast genes encoding syntaxins, SSO1 and SSO2, as suppressors of the temperature-sensitive sec1-1 mutation. We now describe a third suppressor of sec1-1, which we call MSO1. Unlike SSO1 and SSO2, MSO1 is specific for sec1 and does not suppress mutations in any other SEC genes. MSO1 encodes a small hydrophilic protein that is enriched in a microsomal membrane fraction. Cells that lack MSO1 are viable, but they accumulate secretory vesicles in the bud, indicating that the terminal step in secretion is partially impaired. Moreover, loss of MSO1 shows synthetic lethality with mutations in SEC1, SEC2, and SEC4, and other synthetic phenotypes with mutations in several other late-acting SEC genes. We further found that Mso1p interacts with Sec1p both in vitro and in the two-hybrid system. These findings suggest that Mso1p is a component of the secretory vesicle docking complex whose function is closely associated with that of Sec1p.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biological Transport
  • Cloning, Molecular
  • Fungal Proteins / genetics*
  • Fungal Proteins / metabolism
  • Gene Expression Regulation, Fungal
  • Membrane Proteins / genetics*
  • Membrane Proteins / metabolism
  • Membrane Transport Proteins
  • Qa-SNARE Proteins
  • SEC Translocation Channels
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins*


  • Fungal Proteins
  • MSO1 protein, S cerevisiae
  • Membrane Proteins
  • Membrane Transport Proteins
  • Qa-SNARE Proteins
  • SEC Translocation Channels
  • SSO1 protein, S cerevisiae
  • SSO2 protein, S cerevisiae
  • SSS1 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins