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Updated: Jul 10, 2026
06:47
ABCG5/G8 Crystallization in a Lipidic Bicelle Environment for X-Ray Crystallography
Published on: August 25, 2023
Flexibility in the ABC transporter MsbA: Alternating access with a twist
Andrew Ward1, Christopher L Reyes, Jodie Yu
1Departments of Cell Biology and Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, CB-105, La Jolla, CA 92037, USA.
Summary
Structural analysis of ATP-binding cassette (ABC) transporters reveals how nucleotide binding drives conformational changes. These dynamics are crucial for the transport of substrates across cell membranes, highlighting the flexibility of lipid flippases like MsbA.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Biology
Background:
- ATP-binding cassette (ABC) transporters are essential membrane proteins involved in substrate translocation across cellular membranes.
- These transporters are highly conserved across diverse organisms, from bacteria to humans.
- MsbA is a bacterial ABC transporter crucial for lipid transport.
Purpose of the Study:
- To elucidate the conformational changes of the bacterial ABC lipid flippase, MsbA, during its transport cycle.
- To understand the role of nucleotide binding in modulating MsbA conformation and function.
Main Methods:
- Comparison of four X-ray crystal structures of MsbA.
- Analysis of MsbA structures in both nucleotide-bound and nucleotide-free states.
- Detailed examination of structural rearrangements, including extracellular loops and transmembrane helices.
Main Results:
- Nucleotide-free MsbA exhibits a flexible hinge (extracellular loops 2 and 3) allowing nucleotide-binding domain dissociation.
- Nucleotide binding induces a rearrangement of transmembrane helices, altering transporter accessibility.
- Distinct sets of transmembrane helix interactions mediate inward and outward facing conformations.
- Conformational dynamics suggest significant motion is required for MsbA-mediated substrate transport.
Conclusions:
- The study reveals the dynamic nature of ABC transporters, particularly the bacterial lipid flippase MsbA.
- Nucleotide binding is a key driver of conformational changes essential for the transport mechanism.
- MsbA's structural flexibility facilitates the translocation of substrates across the membrane.
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