Abstract
The yeast phosphoinositide phosphatase Sac1p localizes to endoplasmic reticulum (ER) and Golgi membranes and has compartment-specific functions in these organelles. In this study we analyzed in detail the topology of Sac1p. Our data show that Sac1p is a type II transmembrane protein with a large N-terminal cytosolic domain, which is anchored in the membrane by the two potential transmembrane helices near the C terminus. Based on this topology, we created a mutation that caused retention of Sac1p in the ER and as a consequence showed specific alterations in cellular phosphoinositide levels. Our results suggest that Sac1p controls a pool of phosphatidylinositol 3-phosphate and phosphatidylinositol 4-phosphate in the ER. Retention of Sac1p in the ER also stimulates ATP transport into the ER lumen but causes the same Golgi-specific defects that are seen in a sac1 null mutant. Taken together this study provides evidence that Sac1p is an important 4-phosphatase in the ER controlling different aspects of ER-based protein processing and secretion.
Original language | English (US) |
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Pages (from-to) | 10547-10554 |
Number of pages | 8 |
Journal | Journal of Biological Chemistry |
Volume | 277 |
Issue number | 12 |
DOIs | |
State | Published - Mar 22 2002 |
Externally published | Yes |
ASJC Scopus subject areas
- Biochemistry
- Molecular Biology
- Cell Biology