An electron spin resonance study of the Mn(II) and Cu(II) complexes of the Fur repressor protein

Abstract

EPR spectra of Mn(II) Fur complex suggested the presence of Mn(II) in one site per Fur monomer in which Mn(II) is present in a low symmetry environment. The binding of the Mn(II) Fur complex to a DNA fragment “iron box” has a slight broadening effect on the Mn(II) signal and hence it altered the symmetry of the Mn(II) environment. We also report EPR spectra of Cu(II) Fur and Cu(II) C92S C95S mutant Fur complexes as models for Fe(II) complexes; the anisotropic g values and A values observed indicate the presence of Cu(II) in two different environments in the protein; a major axially distorted Cu(II) site bound to nitrogen and a minor distorted tetrahedral sulfur bound to the Cu(II) site. The effect of metal ion on Fur DNA binding is also discussed.