Determination of the exchange integral in binuclear iron-sulfur clusters in proteins of varying complexity

• Published in: Biochimica et biophysica acta Vol. 494; no. 1; pp. 191 - 197
• Main Authors: Salerno, J.C., Ohnishi, Tomoko, Blum, Haywood, Leigh, J.S.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 27.09.1977
• Subjects: Adrenodoxin; Electron Spin Resonance Spectroscopy; Iron-Sulfur Proteins; Metalloproteins; NADH, NADPH Oxidoreductases; Succinate Dehydrogenase; Temperature; Ubiquinone
• ISSN: 0005-2795; 0006-3002; 1879-2952
• DOI: 10.1016/0005-2795(77)90147-7

The coupling constants J between the iron atoms in ferredoxin type iron-sulfur proteins containing binuclear clusters were evaluated by two parallel methods. The temperature dependence of the EPR linewidths and integrated absorption intensities are both related to the energy of the first excited state. The values of J obtained were: center S-1 in succinate dehydrogenase, 90 cm −1; Rieske's iron-sulfur center, 65 cm −1; adrenodoxin, 270 cm −1. The behavior of iron-sulfur center N-1a in NADH:UQ reductase was also examined; its similarity to that of center S-1 indicates that center N-1a is also a binuclear iron-sulfur center, with J = 90 cm −1 . Greater rhombic distortion present in the EPR spectrum of a binuclear cluster was associated with smaller values of J.