Iron-storage protein that displays ferroxidase activity, catalyzing the oxidation of Fe(2+) ions into Fe(3+) ions, that can then be deposited as a ferric-oxide mineral core within the central cavity of the protein complex. 4 Fe(2+) + 4 H(+) + O2 = 4 Fe(3+) + 2 H2O Homooligomer of 24 subunits that are packed together to form an approximately spherical molecule with a central cavity, in which large amounts of iron can be stored. Repressed by Rip1, highly induced by metal chelator phenanthroline in the absence of Rip1. Belongs to the ferritin family. Prokaryotic subfamily. Truncated N-terminus.