GRLMR and SeR models were aligned in PyMOL 57 to assess their similarity. The RMSDCα between models was calculated to be 0.963 Å, indicating very high structural homology as shown visually in figure 2a. The main differences between GRLMR and SeR result from two amino acid mutations: L314H and D408E. The D408E mutation sits at the homodimer interface and is 16 Å away from the closest catalytic cysteine residue (C45). The chemical change is small (aspartic acid being replaced by glutamic acid) and there is no obvious change between the GRLMR and SeR models at this position. Combined this analysis suggests that the D408E mutation is functionally a silent mutation.