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Updated: Dec 19, 2025
09:52
A Fluorescence-based Assay of Phospholipid Scramblase Activity
Published on: September 20, 2016
14.4K
Crystal structure of a human plasma membrane phospholipid flippase
Hanayo Nakanishi1, Katsumasa Irie1,2, Katsumori Segawa3
1Cellular and Structural Physiology Institute, Nagoya University, Nagoya, Japan.
The Journal of Biological Chemistry
|June 5, 2020
Summary
The ATP11C-CDC50A complex structure reveals a pathway for phosphatidylserine transport across the plasma membrane. This flippase complex facilitates phospholipid movement, maintaining cell asymmetry.
Area of Science:
- Membrane Biology
- Structural Biology
- Biochemistry
Background:
- The P4-ATPase flippase ATP11C is crucial for maintaining plasma membrane asymmetry by translocating phosphatidylserine.
- Understanding the structural basis of this transport is key to cellular lipid homeostasis.
Purpose of the Study:
- To elucidate the structure of the human ATP11C-CDC50A flippase complex in a stabilized E2P conformation.
- To identify the pathway and mechanisms involved in phosphatidylserine translocation across the plasma membrane.
Main Methods:
- X-ray crystallography was used to determine the structure of the ATP11C-CDC50A complex.
- Analysis of electron densities to identify bound phospholipids.
Main Results:
- The crystal structure revealed a deep crevice extending from the cell surface to the phospholipid occlusion site.
- An outward-open E2P state was observed, with phosphatidylserines identified in the crevice and an exoplasmic cavity.
- Mutations in binding sites or the transport path impaired ATPase and transport activities.
Conclusions:
- The identified crevice serves as the conduit for phosphatidylserine translocation.
- The exoplasmic cavity is likely involved in phospholipid recognition.
- The study provides insights into the mechanism of phosphatidylserine incorporation into the plasma membrane.
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