ABSTRACT
Ferritin is composed of a protein shell and of iron-containing microcrystals within the protein cavity. The soluble molecule exhibits a molecular mass between 400 kDa and 550 kDa depending on the organism chosen and the iron content. Mossbauer spectroscopy is an excellent tool for analyzing the electronic state of iron. The internal field at the iron nucleus depends on the number of unpaired electrons surrounding the nucleus. An important role in iron deposition in apoferritin has been attributed to phosphate. Numerous reducing agents, including dithionite, thiols, ascorbate, dihydroflavins, and superoxide have been shown to enable reductive release. However, in the absence of a chelator all the reduced iron is retained in the protein shell, and for each reduced iron ion two protons are transferred to the core. The different strategies of iron storage by fungi may turn out to be useful traits in taxonomic classification, evolutionary analysis, and environmental monitoring.
