Conservation of the WxxxE motif. (A). Sequence alignment of the WxxxE containing T3SS effectors Map, IpgB1 and SifA; the bacterial TIR proteins BtpA, BtpB, PdTir, TcpC and TlpA; and eukaryotic hTLR2, hTIRAP and hMyD88. (B). Structural comparison of Map (yellow) and BtpA (slate) structure depicted as ribbons and highlighting the residues W and E (purple), and catalytic and BB loops (blue). Side chains are shown in ball and sticks for the residues involved in the structural scaffold (see text for details). (C). Comparison of the WxxxE motif (with W and E residues shown as red balls and sticks) and BB loop (blue) organisation in the structures of PdTir (gold), TLR2 (green) and TIRAP (wheat).