A Fluorescence-Based Flippase Assay to Monitor Lipid Transport by Drs2-Cdc50

Area of Science:

• Membrane Biology
• Protein Biochemistry
• Biophysical Chemistry

Background:

• Flippases are essential transmembrane proteins regulating lipid asymmetry in biological membranes.
• Reconstitution into artificial vesicles is vital for studying flippase function under controlled conditions.
• The yeast Drs2-Cdc50 complex translocates phosphatidylserine across the trans-Golgi network membrane.

Purpose of the Study:

• To describe a robust protocol for reconstituting the Drs2-Cdc50 flippase complex into liposomes.
• To enable functional characterization of the flippase in a defined membrane environment.
• To provide a platform for analyzing lipid transport and ATP hydrolysis.

Main Methods:

• Incorporation of the Drs2-Cdc50 complex into liposomes using a zwitterionic detergent.
• Detergent removal via dialysis to preserve protein function.
• Activity evaluation using a fluorescence-based lipid transport assay and an ATPase assay with an ATP-regenerating system.

Main Results:

• Successful reconstitution of functional Drs2-Cdc50 complex in liposomes.
• Demonstration of phosphatidylserine translocation across the artificial membrane.
• Quantification of ATP hydrolysis coupled to lipid transport.

Conclusions:

• The described dialysis-based reconstitution method is gentle and effective for preserving flippase activity.
• The combined ATPase and lipid transport assays provide a comprehensive platform for flippase functional analysis.
• This protocol facilitates the study of flippase mechanisms in a chemically defined system.