A ligand field analysis of the spectroscopic differences between rubredoxin and desulforedoxin in the reduced state.

We propose a ligand field model to interpret the differences between the spectroscopic properties of reduced rubredoxin and desulforedoxin. The experimental data are well reproduced by using a common set of ligand field parameters and slightly different values of the mixing parameter theta for the two proteins. In this class of iron-sulfur clusters, the rhombic distortion could be modulated by variations of the S-Fe-S angles.