Structure-based sequence alignment of the five solved alanine racemase structures from Gram-positive bacteria. Structures are from S. pneumoniae, G. stearothermophilus , E. faecalis , B. anthracis  and S. lavendulae . The black box encloses the conserved PLP binding site, the asterisks (*) mark the PLP-bound Lys residue and the catalytic Tyr residue, the diamond (♦) marks the location of the carbamylated Lys residue, and the residues constituting the entryway to the active site are marked with either I (inner layer) or M (middle layer). Residues that form intermonomer interfaces are highlighted in light green. The purple shading is proportional to the degree of sequence identity across the alignment.