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1H NMR studies of the Fe7S8 ferredoxin from Bacillus schlegelii: a further attempt to understand Fe3S4 clusters |
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| Authors: | Shigetoshi Aono I Bertini J A Cowan Claudio Luchinat Antonio Rosato Maria Silvia Viezzoli |
| Institution: | (1) Department of Chemistry, University of Florence, Via Gino Capponi 7, I-50121 Florence, Italy, IT;(2) School of Materials Science, Japan Advanced Institute of Science and Technology, Japan, JP;(3) Department of Chemistry, Ohio State University, USA, US;(4) Institute of Agricultural Chemistry, University of Bologna, Italy, IT |
| Abstract: | The oxidized Fe7S8 ferredoxin from Bacillus schlegelii, containing both Fe3S4]+ and Fe4S4]2+ clusters, has been investigated by 1H NMR spectroscopy. An extensive sequence-specific assignment of the hyperfine-shifted resonances has been obtained by making use of a computer-generated structural model. The pattern and the temperature dependence of the hyperfine shifts of the β-CH2 protons of the cysteines coordinating the Fe3S4]+ cluster are rationalized in terms of magnetic interactions between the iron ions. The same approach holds for the hyperfine coupling with 57Fe. It is shown that the magnetic interactions are more asymmetric in Fe7S8 ferredoxins than in Fe3S4 ferredoxins. The NMR non-observability of the β-CH2 protons of coordinated cysteines in the one-electron-reduced form has been discussed. Received: 19 June 1996 / Accepted: 2 August 1996 |
| Keywords: | Ferredoxin Iron-sulfur clusters NMR Hyperfine shifts Magnetic interactions |
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