Multiple sequence alignment of TIR domains. Amino-acid sequences from the TIR domains of Arabidopsis RPS4 (residues 15–191), Arabidopsis SNC1 (10–180), Arabidopsis RPP1-WsA (50–229), tobacco N (10–191) and Arabidopsis RRS1 (6–153) were aligned with the sequences of TIR domains with known crystal structures, Arabidopsis AtTIR (PDB entry 3jrn; Chan et al., 2010 ▶) and flax L6 (PDB entry 3ozi; Bernoux et al., 2011), using MUSCLE (Edgar, 2004 ▶). The positions of the secondary-structure elements in L6 are shown at the top. The alignment was formatted using ESPript (Gouet et al., 2003 ▶).