期刊
CURRENT BIOLOGY
卷 21, 期 2, 页码 149-153出版社
CELL PRESS
DOI: 10.1016/j.cub.2010.12.031
关键词
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资金
- Cornell-Rockefeller-Sloan-Kettering Tri-Institutional Training Program in Chemical Biology
- Ellison Medical Foundation
- Allene Reuss Memorial Trust
- Crowley Family Fund
- Karl Kirchgessner Foundation
- Ruth and Milton Steinbach Foundation
- Milstein Chemistry Core Facility
- National Institutes of Health
Polar lipids must flip-flop rapidly across biological membranes to sustain cellular life [1, 2], but flipping is energetically costly [3] and its intrinsic rate is low. To overcome this problem, cells have membrane proteins that function as lipid transporters (flippases) to accelerate flipping to a physiologically relevant rate. Flippases that operate at the plasma membrane of eukaryotes, coupling ATP hydrolysis to unidirectional lipid flipping, have been defined at a molecular level [2]. On the other hand, ATP-independent bidirectional flippases that translocate lipids in biogenic compartments, e.g., the endoplasmic reticulum, and specialized membranes, e.g., photoreceptor discs [4, 5], have not been identified even though their activity has been recognized for more than 30 years [1]. Here, we demonstrate that opsin is the ATP-independent phospholipid flippase of photoreceptor discs. We show that reconstitution of opsin into large unilamellar vesicles promotes rapid (tau < 10 s) flipping of phospholipid probes across the vesicle membrane. This is the first molecular identification of an ATP-independent phospholipid flippase in any system. It reveals an unexpected activity for opsin and, in conjunction with recently available structural information on this G protein-coupled receptor [6, 7], significantly advances our understanding of the mechanism of ATP-independent lipid flip-flop.
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