Species-differences of the ligand binding pockets of TLR2/1. Crystal structures of human TLR2 and TLR1 [PDB code 2Z7X], and a model of human TLR6, were viewed in PyMol and non-conserved residues between the human and horse highlighted. (A) Conserved TLR2 ligand-binding residues (cyan) form the majority of contacts, whereas non-conserved (magenta) are at the periphery of the pocket. The TLR1 pocket is lined with conserved residues (yellow); only G313 and V339 (lilac; S317 and I343 in the horse) are non-conserved. (B) L318 (green) and F319 (blue), which interact with Pam2CSK4 (red), are conserved in the horse (I318 and F319). The region surrounding L318 and F319 is conserved apart from F317 (Y317 in the horse; cyan), which lies immediately lateral to L318. F343 and F365 (magenta), which block the TLR6 pocket, are also shown.