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Structural basis for lipopolysaccharide extraction by ABC transporter LptB2FG
Qingshan Luo1,2, Xu Yang1, Shan Yu1
1National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
Nature Structural & Molecular Biology
|April 11, 2017
Summary
The bacterial lipopolysaccharide (LPS) transporter LptB2FG structure reveals a unique mechanism for LPS extraction from the inner membrane. This finding offers insights into bacterial outer membrane biogenesis and potential drug targets.
Area of Science:
- Microbiology
- Structural Biology
- Biochemistry
Background:
- Bacterial lipopolysaccharides (LPS) are essential components of the outer membrane.
- LPS must be transported from the inner membrane to the outer membrane for proper cell envelope assembly.
- The LptB2FG complex is the primary transporter responsible for LPS translocation.
Purpose of the Study:
- To elucidate the structural basis of LPS transport by the LptB2FG complex.
- To understand the mechanism of LPS extraction from the inner membrane.
- To provide insights into the function of ATP-binding cassette (ABC) transporters in LPS biogenesis.
Main Methods:
- X-ray crystallography of the nucleotide-free LptB2FG complex from Pseudomonas aeruginosa.
- Mutational analyses to probe protein function and substrate interaction.
Main Results:
- The crystal structure of nucleotide-free LptB2FG reveals distinct domains within LptF and LptG, including transmembrane domains (TMDs) and periplasmic β-jellyroll-like domains.
- The TMDs of LptF and LptG form a V-shaped cavity in the inner membrane, suggesting a lateral entry point for LPS.
- LPS is proposed to be extracted into the periplasmic domains upon ATP hydrolysis by LptB.
Conclusions:
- The LptB2FG transporter employs a novel mechanism for LPS extraction, differing from classical ABC transporters.
- Structural insights into LptB2FG provide a foundation for understanding LPS transport and bacterial envelope integrity.
- This mechanism highlights a potential target for antimicrobial drug development.