TRAPP stimulates guanine nucleotide exchange on Ypt1p.
TRAPP, a novel complex that resides on early Golgi, mediates the targeting of ER-to-Golgi vesicles to the Golgi apparatus. Previous studies have shown that YPT1, which encodes the small GTP-binding protein that regulates membrane traffic at this stage of the secretory pathway, interacts genetically with BET3 and BET5. Bet3p and ... Bet5p are 2 of the 10 identified subunits of TRAPP. Here we show that TRAPP preferentially binds to the nucleotide-free form of Ypt1p. Mutants with defects in several TRAPP subunits are temperature-sensitive in their ability to displace GDP from Ypt1p. Furthermore, the purified TRAPP complex accelerates nucleotide exchange on Ypt1p. Our findings imply that Ypt1p, which is present on ER-to-Golgi transport vesicles, is activated at the Golgi once it interacts with TRAPP.
Mesh Terms:
Carrier Proteins, Endoplasmic Reticulum, Fungal Proteins, Golgi Apparatus, Guanine Nucleotide Exchange Factors, Guanine Nucleotides, Guanosine Diphosphate, Guanosine Triphosphate, Membrane Proteins, Protein Transport, Saccharomyces cerevisiae Proteins, Transport Vesicles, Vesicular Transport Proteins, rab GTP-Binding Proteins
Carrier Proteins, Endoplasmic Reticulum, Fungal Proteins, Golgi Apparatus, Guanine Nucleotide Exchange Factors, Guanine Nucleotides, Guanosine Diphosphate, Guanosine Triphosphate, Membrane Proteins, Protein Transport, Saccharomyces cerevisiae Proteins, Transport Vesicles, Vesicular Transport Proteins, rab GTP-Binding Proteins
J. Cell Biol.
Date: Oct. 16, 2000
PubMed ID: 11038176
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