FIGURE 23-35 Toll-like receptor activation. The extracellular portions of TLRs recognize ligands of diverse chemical nature (nucleic acids, lipopolysaccharides). The cytoplasmic portions of the TLRs, called TIR (Toll/IL1β receptor homology) domains, associate with the adapter protein MyD88, present in six copies per complex, and recruit two types of kinases, both members of the IRAK family. These complex interactions are maintained by TIR domains and death domains (DD) as shown in the figure. The assembled complex on the cytoplasmic side is referred to as the myddosome. See J. Y. Kang and J.-O. Lee, 2011, Annu. Rev. Biochem. 80:917.

[Data from M. S. Jin et al., 2007, Cell 130:1071, PDB ID 2z7x, and S. C. Lin et al., 2010, Nature 465:885, PDB ID 3mop.]