Alignment of mammalian ferritin H and L subunits. The amino acid numbering is derived from mammalian L subunit sequences, but does not include the additional octapeptide. Both H and L subunits contain residues associated with dimer formation (d) and 3-fold (t) and 4-fold (f) symmetry axes. Identical amino acids are indicated by asterisks. Gaps indicated by dashes were inserted to optimize the alignment. Amino acids associated with iron nucleation sites and ferroxidase activity were underlined and double-underlined, respectively. Sequence data (GenBank accession data) were as follows: feline H (AB193257) and L (AB193258), canine H (AB175610) and L (AB175612), horse H (AY112742) and L (AB175617), bovine H (AB003093) and L (AB003094), human H (NM_002032) and L (NM_000146), rabbit L (X07830), rat H (U58829) and L (NM_022500), mouse H (NM_010239) and L (J04716). Amino acid sequences of cetacean ferritin H and L subunits are from P. crassidens, L. obliquidens, G. griseus, and G. macrorhynchus.