PMID: 16043704 , Related PDB id: 2A0Z

Authors:

Bell JK, Botos I, Hall PR, Askins J, Shiloach J, Segal DM, Davies DR

Title:

The molecular structure of the Toll-like receptor 3 ligand-binding domain.

Journal:

Proc Natl Acad Sci U S A. 2005 Aug 2;102(31):10976-80. Epub 2005 Jul 25.

Abstract:

Innate immunity is the first line of defense against invading pathogens. Toll-like receptors (TLRs) act as sentinels of the innate immune system, sensing a variety of ligands from lipopolysaccharide to flagellin to dsRNA through their ligand-binding domain that is composed of leucine-rich repeats (LRRs). Ligand binding initiates a signaling cascade that leads to the up-regulation of inflammation mediators. In this study, we have expressed and crystallized the ectodomain (ECD) of human TLR3, which recognizes dsRNA, a molecular signature of viruses, and have determined the molecular structure to 2.4-A resolution. The overall horseshoe-shaped structure of the TLR3-ECD is formed by 23 repeating LRRs that are capped at each end by specialized non-LRR domains. The extensive beta-sheet on the molecule's concave surface forms a platform for several modifications, including insertions in the LRRs and 11 N-linked glycans. The TLR3-ECD structure indicates how LRR loops can establish distinct pathogen recognition receptors.