An acidic sequence of a putative yeast Golgi membrane protein binds COPII and facilitates ER export.
We previously identified Sys1p as a high copy number suppressor of Ypt6 GTPase-deficient yeast mutants that are defective in endosome-to-Golgi transport. Here, we show that Sys1p is an integral membrane protein that resides on a post-endoplasmic reticulum (ER) organelle(s). Affinity studies with detergent- solubilized yeast proteins showed that the C-terminal ... 53 amino acid tail of Sys1p binds effectively to the cytoplasmic Sec23p-Sec24p COPII subcomplex. This binding required a di-acidic Asp-Leu-Glu (DXE) motif, previously shown to mediate efficient ER export of the vesicular stomatitis virus glycoprotein in mammalian cells. In Sys1p, a Glu-Leu-Glu (EXE) sequence could not substitute for the (DXE) motif. Mutations of the (DXE) sequence resulted in ER retention of approximately 30% of the protein at steady state, whereas addition of the Sys1p tail to an ER-resident membrane protein led to an intracellular redistribution of the chimeric protein. Our study demonstrates for the first time that, in yeast, a di-acidic sequence motif can act as a sorting signal for cargo selection during the formation of transport vesicles at the ER by direct binding to COPII component(s).
Mesh Terms:
Amino Acid Motifs, Amino Acid Sequence, Animals, COP-Coated Vesicles, Cell Membrane, Cloning, Molecular, Cytoplasm, Dimerization, Endopeptidases, Endoplasmic Reticulum, Epitopes, Escherichia coli, GTP Phosphohydrolases, Glutathione Transferase, Golgi Apparatus, Intracellular Membranes, Membrane Glycoproteins, Membrane Proteins, Molecular Sequence Data, Monomeric GTP-Binding Proteins, Mutation, Plasmids, Protein Binding, Protein Structure, Tertiary, Protein Transport, Recombinant Fusion Proteins, Saccharomyces cerevisiae Proteins, Sequence Homology, Amino Acid, Subcellular Fractions, Temperature, Time Factors, Vesicular Transport Proteins, Viral Envelope Proteins
Amino Acid Motifs, Amino Acid Sequence, Animals, COP-Coated Vesicles, Cell Membrane, Cloning, Molecular, Cytoplasm, Dimerization, Endopeptidases, Endoplasmic Reticulum, Epitopes, Escherichia coli, GTP Phosphohydrolases, Glutathione Transferase, Golgi Apparatus, Intracellular Membranes, Membrane Glycoproteins, Membrane Proteins, Molecular Sequence Data, Monomeric GTP-Binding Proteins, Mutation, Plasmids, Protein Binding, Protein Structure, Tertiary, Protein Transport, Recombinant Fusion Proteins, Saccharomyces cerevisiae Proteins, Sequence Homology, Amino Acid, Subcellular Fractions, Temperature, Time Factors, Vesicular Transport Proteins, Viral Envelope Proteins
EMBO J.
Date: Dec. 03, 2001
PubMed ID: 11726510
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