PMID:15611257
| Citation |
Tsuneyoshi, N, Fukudome, K, Kohara, J, Tomimasu, R, Gauchat, JF, Nakatake, H and Kimoto, M (2005) The functional and structural properties of MD-2 required for lipopolysaccharide binding are absent in MD-1. J. Immunol. 174:340-4 |
|---|---|
| Abstract |
MD-1 and MD-2 are secretory glycoproteins that exist on the cell surface in complexes with transmembrane proteins. MD-1 is anchored by radioprotective 105 (RP105), and MD-2 is associated with TLR4. In vivo studies revealed that MD-1 and MD-2 have roles in responses to LPS. Although the direct binding function of MD-2 to LPS has been observed, the physiological function of MD-1 remains unknown. In this study, we compared the LPS-binding functions of MD-1 and MD-2. LPS binding to cell surface complexes was detected for cells transfected with TLR4/MD-2. In contrast, binding was not observed for RP105/MD-1-transfected cells. When rMD-2 protein was expressed in Escherichia coli, it was purified in complexes containing LPS. In contrast, preparations of MD-1 did not contain LPS. When rMD-2 protein was prepared in a mutant strain lacking the lpxM gene, LPS binding disappeared. Therefore, the secondary myristoyl chain attached to the (R)-3-hydroxymyristoyl chain added by LpxM is required for LPS recognition by MD-2, under these conditions. An amphipathic cluster composed of basic and hydrophobic residues in MD-2 has been suggested to be the LPS-binding site. We specifically focused on two Phe residues (119 and 121), which can associate with fatty acids. A mutation at Phe(191) or Phe(121) strongly reduced binding activity, and a double mutation at these residues prevented any binding from occurring. The Phe residues are present in MD-2 and absent in MD-1. Therefore, the LPS recognition mechanism by RP105/MD-1 is distinct from that of TLR4/MD-2. |
| Links | |
| Keywords |
Amino Acid Sequence; Animals; Antigens, CD/metabolism; Antigens, Surface/chemistry; Antigens, Surface/genetics; Antigens, Surface/metabolism; Binding Sites/physiology; Carrier Proteins/chemistry; Carrier Proteins/genetics; Carrier Proteins/metabolism; Electrophoresis, Polyacrylamide Gel; Humans; Immunoblotting; Lipopolysaccharides/metabolism; Lymphocyte Antigen 96; Membrane Glycoproteins/metabolism; Molecular Sequence Data; Mutagenesis, Site-Directed; Mutation; Phenylalanine/genetics; Receptors, Cell Surface/metabolism; Toll-Like Receptor 4; Toll-Like Receptors; Transfection |
| edit table |
Significance
You can help EcoliWiki by summarizing why this paper is useful
Useful Materials and Methods
You can help Ecoliwiki by describing the useful materials (strains, plasmids, antibodies, etc) described in this paper.
Annotations
<annotationlinks/>
EcoliWiki Links
Add links to pages that link here (e.g. gene, product, method pages)
References
See Help:References for how to manage references in EcoliWiki.