Fig. 1

a. Domain structures of the CaN A chains from the three human isoforms. The residue numbering for αCaN was taken from the crystal structure (PDBID 1AUI [55];). For the β and γ isoforms, the regions of greatest difference with the α isoform are highlighted. b. Crystal structure of human αCaN (PDBID 1AUI [55];). The A chain is colored blue and the B chain green. The orange and yellow spheres denote a Zn-Fe center in the active site in the catalytic domain and the grey spheres denote Ca²⁺ bound to the B chain. Residues within the A chain between and beyond which electron density is not detected are indicated. The green oval denotes the location of the PxIxIT substrate binding site and the blue oval the LxVP substrate binding site