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 Fe2+ 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 noninteracting, with each individual iron(II) behaving like iron(II) in reduced rubredoxin.