The structure of ferrochelatase (PDB ID: 2QD1) enlarged to show Thr116 (pink). Thr116 interacts with His86 (dark blue) and is near Val85 (dark green). The Thr116-containing α-helix is highlighted with lemon green and the protoporphyrin (purple) is in the active site. From Figure 4D, Chung et al. eLife 6, e24767