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An acidic sequence of a putative yeast Golgi membrane protein binds COPII and facilitates ER export
Author(s) -
Votsmeier Christian,
Gallwitz Dieter
Publication year - 2001
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/20.23.6742
Subject(s) - copii , biology , endoplasmic reticulum , golgi apparatus , vesicular transport proteins , microbiology and biotechnology , biochemistry , er retention , copi , transport protein , secretory pathway , saccharomyces cerevisiae , mutant , yeast , vacuolar protein sorting , gene
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 ∼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).