Abstract
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.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Carrier Proteins / metabolism*
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Endoplasmic Reticulum / metabolism
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Fungal Proteins / metabolism
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Golgi Apparatus / metabolism
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Guanine Nucleotide Exchange Factors / metabolism*
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Guanine Nucleotides / metabolism*
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Guanosine Diphosphate / metabolism
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Guanosine Triphosphate / metabolism
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Membrane Proteins / metabolism*
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Protein Transport
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Saccharomyces cerevisiae Proteins*
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Transport Vesicles / metabolism
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Vesicular Transport Proteins*
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rab GTP-Binding Proteins / metabolism*
Substances
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BET3 protein, S cerevisiae
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BET5 protein, S cerevisiae
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Carrier Proteins
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Fungal Proteins
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Guanine Nucleotide Exchange Factors
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Guanine Nucleotides
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Membrane Proteins
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Saccharomyces cerevisiae Proteins
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Vesicular Transport Proteins
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transport protein particle, TRAPP
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Guanosine Diphosphate
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Guanosine Triphosphate
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YPT1 protein, S cerevisiae
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rab GTP-Binding Proteins