Mon2, a Relative of Large Arf Exchange Factors, Recruits Dop1 to the Golgi Apparatus

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...

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Bibliographic Details
Published in:The Journal of biological chemistry 2006-01, Vol.281 (4), p.2273-2280
Main Authors: Gillingham, Alison K., Whyte, James R.C., Panic, Bojana, Munro, Sean
Format: Article
Language:English
Subjects:
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
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Summary: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.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M510176200