1. Concentrative sorting of secretory cargo proteins into COPII-coated vesicles
- Author
-
Per Malkus, Feng Jiang, and Randy Schekman
- Subjects
Saccharomyces cerevisiae Proteins ,Amino Acid Transport Systems ,Immunoblotting ,Molecular Sequence Data ,Saccharomyces cerevisiae ,Biology ,Protein Sorting Signals ,Endoplasmic Reticulum ,Cytosol ,Microsomes ,Report ,intracellular membranes ,endoplasmic reticulum ,COPII-coated vesicle ,protein transport ,protein sorting signals ,Amino Acid Sequence ,Protein Precursors ,COPII ,Sequence Homology, Amino Acid ,Vesicle ,Endoplasmic reticulum ,Cell Membrane ,Cell Biology ,COP-Coated Vesicles ,Cell biology ,Transport protein ,Protein Structure, Tertiary ,Protein Transport ,Secretory protein ,Membrane protein ,Databases as Topic ,ras GTPase-Activating Proteins ,Mutation ,Plasmids ,Signal Transduction - Abstract
Here, we show that efficient transport of membrane and secretory proteins from the ER of Saccharomyces cerevisiae requires concentrative and signal-mediated sorting. Three independent markers of bulk flow transport out of the ER indicate that in the absence of an ER export signal, molecules are inefficiently captured into coat protein complex II (COPII)-coated vesicles. A soluble secretory protein, glycosylated pro-alpha-factor (gpalphaf), was enriched approximately 20 fold in these vesicles relative to bulk flow markers. In the absence of Erv29p, a membrane protein that facilitates gpalphaf transport (Belden and Barlowe, 2001), gpalphaf is packaged into COPII vesicles as inefficiently as soluble bulk flow markers. We also found that a plasma membrane protein, the general amino acid permease (Gap1p), is enriched approximately threefold in COPII vesicles relative to membrane phospholipids. Mutation of a diacidic sequence present in the COOH-terminal cytosolic domain of Gap1p eliminated concentrative sorting of this protein.
- Published
- 2002