Individual Reduction Potentials of the Iron Ions in Fe(2)S(2) and High-Potential Fe(4)S(4) Ferredoxins.
The DelPhi program package has been used to confirm that the span in reduction potentials among high-potential Fe(4)S(4) ferredoxins must be mainly ascribed to the net protein charges arising from acidic and basic residues. Subsequently, the order of the individual reduction potentials of the iron ions in Fe(2)S(2) ferredoxins as found from NMR spectroscopy was explained mainly on the basis of different solvation contributions to the electrostatic potential. The individual reduction potentials of the iron ions in high-potential Fe(4)S(4) ferredoxins, again available from NMR spectroscopy, are only qualitatively reproduced. It is proposed that the protein triggers a distortion in the cluster which would be a further contribution to the electrochemical inequivalence of the individual iron ions.
Banci
Lucia
L
Department of Chemistry, University of Florence, Florence, Italy, and Institute of Agricultural Chemistry, University of Bologna, Bologna, Italy.
Bertini
Ivano
I
Gori Savellini
Giovanni
G
Luchinat
Claudio
C