Ferritin from the spleen of the Antarctic teleost Trematomus bernacchii

Ferritin from the spleen of the Antarctic teleost Trematomus bernacchii is an iron storage protein composed of a single subunit type whose amino N-ter minal sequence is blocked, as in L-type mammalian and fish ferritin polypep tide chains. The partial amino acid sequence reveals at high similarity wit h 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 subunits, t he T. bernacchii chain contains the ferroxidase center, typical of mammalia n H chains, and the glutamate residues of the iron micelle nucleation site, typical of mammalian L chains. It follows that, at variance with the mamma lian ferritins, a single chain suffices to carry out both ferritin function s. In accordance with the sequence data, the T. bernacchii ferritin homopol ymer is endowed with a high rate of iron oxidation and a high iron accumula tion capacity.