Fig 1: Pairwise alignment of human and mouse S100A8 and S100A9 proteins. (A) The structure of human calprotectin (PDB ID 4GGF) in complex with manganese (red spheres). The side chains of the metal-binding sites are included in stick representation. (B) A sequence alignment of human and mouse S100A8 and S100A9, with mapped secondary structure elements. Sequences for human (AAH05928.1) and mouse (NP_038678.1) S100A8 proteins were aligned through Geneious with a BLOSUM 65 matrix. The S100A8 sequences share 58% identity and 83% sequence similarity. Mouse S100A8 is 89 amino acids in length, whereas human S100A8 is 93 amino acids in length. Sequences for human (AAH47681.1) and mouse (NP_001268781.1) S100A9 proteins were aligned and shared 58% identity and 74% sequence similarity. Mouse S100A9 is 113 residues in length, whereas human S100A9 is 114 residues in length. Residues making up the site 1 and site 2 metal-binding sites are indicated by magenta and cyan arrows, respectively. (C) Based on the sequence alignment in panel B, residues that are different between human and mouse calprotectin are colored blue on the surface of the human calprotectin. The most divergent regions between the two are found on one side of site 1 and on the diametrically opposed side of the site 2 metal-binding site (indicated by the dashed circles).