Faculty Collaboration Database

The LptC transmembrane helix undergoes a rigid body movement upon LptB₂FG cavity collapse. Protein Sci 2025 May;34(5):e70133

Date

04/22/2025

Pubmed ID

40260908

Pubmed Central ID

PMC12012751

DOI

10.1002/pro.70133

Scopus ID

2-s2.0-105003897746 (requires institutional sign-in at Scopus site)   2 Citations

Abstract

Lipopolysaccharide (LPS) is an essential component of the cellular envelope of Gram-negative bacteria and contributes to antibiotic resistance and pathogenesis. Proper localization of LPS at the outer membrane is facilitated via seven distinct LPS transport (Lpt) proteins that bridge the inner and outer membranes. Mature LPS diffuses into the membrane cavity of the inner membrane ABC transporter LptB₂FGC through a lateral gate formed by the LptF and LptG transmembrane (TM) helices. The TM helix of LptC intercalates within the LPS entry point and has been shown to regulate the ATPase activity of LptB₂FG and contribute to thermal stability. Determination of the LptB₂FGC open state structure revealed the location of the LptC TM helix within the membrane complex. However, in the closed state structure, the LptC TM helix is unresolved, suggesting the helix may be displaced from the lateral gate prior to or upon closure of the cavity. To determine the conformational states of the LptC TM helix in the open and closed LptB₂FGC conformations, we utilized site-directed spin labeling in combination with both continuous wave electron paramagnetic resonance (EPR) and double electron electron resonance (DEER) spectroscopies to investigate the LptC TM helix and linker region. These data indicate that the LptC TM helix undergoes a rigid body movement away from the central LptB₂FG cavity upon cavity closure. The findings presented here will support structure-based drug design optimization of recently discovered antibiotics that bind LptB₂FG and occlude the LptC TM helix from the lateral gate.

Author List

Cina NP, Klug CS

Authors

Nicholas P. Cina Postdoctoral Researcher in the Biophysics department at Medical College of Wisconsin
Candice S. Klug PhD Professor in the Biophysics department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

ATP-Binding Cassette Transporters
Escherichia coli
Escherichia coli Proteins
Lipopolysaccharides
Membrane Proteins
Models, Molecular
Protein Conformation, alpha-Helical