Mössbauer studies on iron(II)‐substituted yeast metallothionein

Iron(II)‐substituted yeast metallothionein has been studied with Mössbauer spectroscopy. The iron in the protein is in the high‐spin ferrous state. A maximum metal content of four iron(II)/molecule has been determined, with the four metal ions forming a diamagnetic cluster due to the antiferromagnetic exchange interaction between Fe 2+ via bridging thiolates. In the case where the iron titration gives a value of less than four iron(II)/apoprotein, the metal ions are magnetically non‐interacting, with each individual iron(II) behaving like iron(II) in reduced rubredoxin.