Mon2, a relative of large Arf exchange factors, recruits Dop1 to the Golgi apparatus

J Biol Chem. 2006 Jan 27;281(4):2273-80. doi: 10.1074/jbc.M510176200. Epub 2005 Nov 21.


The protein Mon2 is distantly related to the guanine nucleotide exchange factors (GEFs) that activate Arf1 on Golgi membranes. However, unlike these "large" Arf GEFs, Mon2 lacks the Sec7 domain that catalyzes nucleotide exchange on Arf1. Here we report that yeast Mon2 shares extensive homology with the noncatalytic parts of both the BIG and Golgi brefeldin A resistance factor subfamilies of Arf GEFs and is located to the trans-Golgi. Moreover, we find that Mon2 forms a complex with Dop1, a large cytoplasmic protein conserved in evolution from humans to protozoa. Deletion of Mon2 results in mislocalization of Dop1 from the Golgi and defects in cycling between endosomes and the Golgi. However, unlike Mon2, Dop1 is essential for yeast viability. A conditional allele of Dop1 shows that loss of Dop1 activity not only affects endosome to Golgi transport but also causes a severe perturbation of the organization of the endoplasmic reticulum. Thus, it appears that Dop1 plays a widespread role in membrane organization, and Mon2 acts as a scaffold to recruit the Golgi-localized pool of Dop1.

MeSH terms

  • Alleles
  • Amino Acid Sequence
  • Cytoplasm / metabolism
  • Endoplasmic Reticulum / metabolism
  • Endoplasmic Reticulum / ultrastructure
  • Endosomes / metabolism
  • Gene Deletion
  • Golgi Apparatus / metabolism*
  • Green Fluorescent Proteins / metabolism
  • Guanine Nucleotide Exchange Factors / chemistry
  • Microscopy, Electron
  • Microscopy, Video
  • Molecular Sequence Data
  • Plasmids / metabolism
  • Protein Binding
  • Protein Structure, Tertiary
  • Recombinant Fusion Proteins / chemistry
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / chemistry*
  • Saccharomyces cerevisiae Proteins / physiology
  • Sequence Homology, Amino Acid
  • Temperature
  • Vesicular Transport Proteins


  • Dop1 protein, S cerevisiae
  • Guanine Nucleotide Exchange Factors
  • MON2 protein, S cerevisiae
  • Recombinant Fusion Proteins
  • Saccharomyces cerevisiae Proteins
  • Vesicular Transport Proteins
  • Green Fluorescent Proteins