Ferritin from the spleen of the Antarctic teleostTrematomus bernacchii

Ferritin from the spleen of the Antarctic teleost Trematomus bernacchii is an iron storage protein composed of a single sub‐unit type whose amino N‐terminal sequence is blocked, as in L‐type mammalian and fish ferritin polypeptide chains. The partial amino acid sequence reveals a high similarity with the cDNA‐deduced sequence of the M chain (L‐type) of Salmo salar and the H1 chain of Salmo gairdneri ferritins. Like those of the latter sub‐units, the T. bernacchii chain contains the ferroxidase center, typical of mammalian H chains, and the glutamate residues of the iron micelle nucleation site, typical of mammalian L chains. It follows that, at variance with the mammalian ferritins, a single chain suffices to carry out both ferritin functions. In accordance with the sequence data, the T. bernacchii ferritin homopolymer is endowed with a high rate of iron oxidation and a high iron accumulation capacity.