FBXLS's N-terminus encodes an iron-binding hemerythrin domain. A Schematic of the predicted a-helices (cylinders), conserved iron-binding ligands (magenta), and possible iron-binding ligands (pink) in the human FBXL5 hemerythrin domain. Helical bounds for the FBXL5 were determined by combining information from helices observed in other structures with predictions from sequence alignments. B Model of the FBXL5 hemerythrin domain mapped upon a solved hemerythrin structure (2pOn). Six conserved Fe-binding residues are colored magenta and residues that could replace the seventh Fe-binding residue are colored pink.