An homology model of full-length MCR-1 (Figure ) was created using Modeller v. 9.17 , using the N. meningitidis EptA 14 structure (PDB 5FGN, 35.6 % sequence identity) as a template. To create a dizinc starting structure, the second zinc equivalent was positioned by aligning this model with the structure of the MCR-1 catalytic domain in the di-zinc form (PDB 5LRM ). The final model comprises MCR-1 residues 11 -541; the first ten residues were excluded as these form an unstructured Nterminal tail far from the active site and have no predicted structural or catalytic function. Phosphorylated Thr285, as found in the structure of MCR-1 in the mono-zinc form (PDBPDB 5LRN ), was modified to threonine and to phosphoethanolaminated threonine (PET) using the builder tool in PyMOL , to replicate the resting and phosphointermediate states, respectively. The sidechain of the phosphoethanolaminated threonine (PET) residue was positioned to avoid sidechain clashes with residues from either domain. The engineered PET residue was parameterized using the RED server with QM optimization using Gaussian .