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Isolation and Chemical Characterization of Lipid A from Gram-negative Bacteria
Published on: September 16, 2013
MD-2 binds to bacterial lipopolysaccharide
S Viriyakosol1, P S Tobias, R L Kitchens
1Veterans Administration San Diego Healthcare System and Department of Pathology and Medicine, University of California San Diego, 92161, USA. sviriyak@ucsd.edu
The Journal of Biological Chemistry
|August 14, 2001
Summary
MD-2 is a protein that binds to lipopolysaccharide (LPS). This binding influences LPS
Area of Science:
- Immunology
- Molecular Biology
- Cellular Biology
Background:
- The lipopolysaccharide (LPS) receptor complex is crucial for innate immunity, but its components' precise functions are not fully understood.
- MD-2 is a known associate of toll-like receptor 4 (TLR4), a key component in LPS recognition.
Purpose of the Study:
- To investigate the direct binding capabilities of recombinant human MD-2 to LPS.
- To elucidate the role of MD-2 within the LPS receptor complex and its impact on cellular responses.
Main Methods:
- Production of recombinant human MD-2.
- Multiple binding assays to assess MD-2's interaction with purified rough LPS from Salmonella minnesota and Escherichia coli.
- Functional assays using TLR4-transfected cells, astrocytoma cells, and human whole blood to evaluate MD-2's effect on LPS-induced cellular activation.
Main Results:
- MD-2 demonstrated direct binding to purified rough LPS, with an apparent dissociation constant (KD) of 65 nm in one assay.
- MD-2 binding to LPS was independent of LPS-binding protein (LBP) and CD14; LBP was found to compete with MD-2 for LPS.
- MD-2 differentially modulated LPS activity: enhancing it in TLR4-transfected cells while inhibiting it in astrocytoma cells and human monocytes.
Conclusions:
- MD-2 is confirmed as a direct lipopolysaccharide-binding protein.
- MD-2's role in regulating cellular activation by LPS is context-dependent, likely influenced by its local availability and interactions within the receptor complex.
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