Mössbauer studies of putidaredoxin

Putidaredoxin is the iron sulfide protein component of an enzyme system which hydroxylates a methylene group with O2 to form a secondary alcohol. It contains, in a molecular weight of 12,000, two atoms each of iron and acid labile sulfur. We have used the Mossbauer effect to study the symmetry of the ligands and the electronic configuration of the iron. These studies were facilitated by the removal of the iron and subsequent replacement with iron-57. Our main conclusions are as follows. The sites of the two iron atoms are identical in the oxidized as well as in the reduced state. In the oxidized state, the spectrum consists of a pure quadrupole doublet, and the absence of magnetic interaction indicates that the electrons on the two iron atoms are coupled to a total spin of zero. The reduced state contains one additional electron which is shared between the two iron atoms and produces an internal field in excess of 200 KG at each iron nucleus. To share an electron, the two iron atoms must be close together. The spectrum of the reduced enzyme also provides evidence for a temperature-dependent relaxation mechanism.U of I OnlyThesi