UMMS Affiliation

Department of Medicine, Division of Infectious Diseases and Immunology

Publication Date


Document Type



Biochemistry, Biophysics, and Structural Biology | Immunology and Infectious Disease | Lipids


Lipopolysaccharide (LPS) activates the innate immune response through the Toll-like receptor 4 (TLR4).MD-2 complex. A synthetic lipid A precursor, lipid IV(A), induces an innate immune response in mice but not in humans. Both TLR4 and MD-2 are required for the agonist activity of lipid IV(A) in mice, with TLR4 interacting through specific surface charges at the dimerization interface. In this study, we used site-directed mutagenesis to identify the MD-2 residues that determine lipid IV(A) species specificity. A single mutation of murine MD-2 at the hydrophobic pocket entrance, E122K, substantially reduced the response to lipid IV(A). Combining the murine MD-2 E122K with the murine TLR4 K367E/S386K/R434Q mutations completely abolished the response to lipid IV(A), effectively converting the murine cellular response to a human-like response. In human cells, however, simultaneous mutations of K122E, K125L, Y41F, and R69G on human MD-2 were required to promote a response to lipid IV(A). Combining the human MD-2 quadruple mutations with the human TLR4 E369K/Q436R mutations completely converted the human MD-2/human TLR4 receptor to a murine-like receptor. Because MD-2 residues 122 and 125 reside at the dimerization interface near the pocket entrance, surface charge differences here directly affect receptor dimerization. In comparison, residues 42 and 69 reside at the MD-2/TLR4 interaction surface opposite the dimerization interface. Surface charge differences there likely affect the binding angle and/or rigidity between MD-2 and TLR4, exerting an indirect influence on receptor dimerization and activation. Thus, surface charge differences at the two MD-2/TLR4 interfaces determine the species-specific activation of lipid IV(A).


Lipopolysaccharide, innate immune response, TLR4, lipid IV(A)

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© 2010 by The American Society for Biochemistry and Molecular Biology, Inc. Publisher PDF posted after 12 months as allowed by the publisher's author rights policy at

DOI of Published Version



This research was originally published in: J Biol Chem. 2010 Sep 3;285(36):27935-43. doi: 10.1074/jbc.M110.134668. Epub 2010 Jun 30. Link to article on publisher's site

Journal/Book/Conference Title

The Journal of biological chemistry

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Link to Article in PubMed

PubMed ID