Figure 6.

Patterns of LRR conservation between NOD1 and NOD2 support a conserved ligand binding surface. (A) Other than the signature residues in the LxxLxLxxNxL motif only three residues – W820, G821, and S846 (NOD1); W907, G908, and S933 (NOD2) – are conserved across all examined species of NOD1 and all mammalian NOD2 sequences. The likely spatial position of these residues on the concave surface of NOD1 is shown. The residue sidechains are represented as red sticks. (B) Heat map representation of the relative similarity of the eight terminal LRR repeats in NOD1 and NOD2 from the human, chimpanzee, mouse, cow, elephant, platypus, and coelacanth. The number in each box represents the average number of identical residues in a cross-species pairwise comparison between the relevant LRR motifs. Boxes are colored on a graded scale from green (most similar) down to red (least similar). (C) The three residues (highlighted red) are found in the X3, X4, and X5 position of the LRR consensus motif. These positions are populated by a wide range of different amino acids (highlighted yellow). K989 and S991 (highlighted in purple), two residues in human NOD2 implicated in ligand recognition and receptor activation, are located in a region of the protein missing in the Actinopterygii due to an exon deletion.