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Characterization of and lipopolysaccharide binding to the E. coli LptC protein dimer. Protein Sci 2018 02;27(2):381-389

Date

10/13/2017

Pubmed ID

29024084

Pubmed Central ID

PMC5775163

DOI

10.1002/pro.3322

Scopus ID

2-s2.0-85040841909   4 Citations

Abstract

Lipopolysaccharide (LPS, endotoxin) is the major component of the outer leaflet of the outer membrane of Gram-negative bacteria such as Escherichia coli and Salmonella typhimurium. LPS is a large lipid containing several acyl chains as its hydrophobic base and numerous sugars as its hydrophilic core and O-antigen domains, and is an essential element of the organisms' natural defenses in adverse environmental conditions. LptC is one of seven members of the lipopolysaccharide transport (Lpt) protein family that functions to transport LPS from the inner membrane (IM) to the outer leaflet of the outer membrane of the bacterium. LptC is anchored to the IM and associated with the IM LptFGB complex. It is hypothesized that LPS binds to LptC at the IM, transfers to LptA to cross the periplasm, and is inserted by LptDE into the outer leaflet of the outer membrane. The studies described here comprehensively characterize and quantitate the binding of LPS to LptC. Site-directed spin labeling electron paramagnetic resonance spectroscopy was utilized to characterize the LptC dimer in solution and monitor spin label mobility changes at 10 sites across the protein upon addition of exogenous LPS. The results indicate that soluble LptC forms concentration-independent N-terminal dimers in solution, LptA binding does not change the conformation of the LptC dimer nor appreciably disrupt the LptC dimer in vitro, and LPS binding affects the entire LptC protein, with the center and C-terminal regions showing a greater affinity for LPS than the N-terminal domain, which has similar dissociation constants to LptA.

Author List

Schultz KM, Klug CS

Author

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

Amino Acid Motifs
Binding Sites
Biological Transport
Crystallography, X-Ray
Escherichia coli
Escherichia coli Proteins
Gene Expression
Hydrophobic and Hydrophilic Interactions
Kinetics
Lipopolysaccharides
Membrane Proteins
Models, Molecular
Mutation
Protein Binding
Protein Conformation, alpha-Helical
Protein Conformation, beta-Strand
Protein Interaction Domains and Motifs
Protein Multimerization
Protein Structure, Tertiary
Protein Transport
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