Characterization of two dissimilatory sulfite reductases from sulfate-reducing bacteria |
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Authors: | B. H. Huynh I. Moura A. R. Lino J. J. G. Moura J. Legall |
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Affiliation: | (1) Department of Physics, Emory University, 30322 Atlanta, GA, USA;(2) Centro de Quimica Estrutural das Universidade de Lisboa, I.S.T., 1000 Lisboa, Portugal;(3) Department of Biochemistry, University of Georgia, 30306 Athens, GA, USA |
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Abstract: | Mössbauer, EPR, and biochemical techniques were used to characterize two dissimilatory sulfite reductases: desulforubidin fromDesulfovibrio baculatus strain DSM 1743 and desulfoviridin fromDesulfovibrio gigas. For each molecule of desulforubidin, there are two sirohemes and four [4Fe?4S] clusters. The [4Fe?4S] clusters are in the diamagnetic 2+ oxidation state. The sirohemes are high-spin ferric (S=5/2) and each siroheme is exchanged-coupled to a [4Fe?4S]2+ cluster. Such an exchange-coupled siroheme-[4Fe?4S] unit has also been found in the assimilatory sulfite reductase fromEscherichia coli/1/ and in a low-molecular weight sulfite reductase fromDesulfovibrio vulgaris/2/. For each molecule of defulfoviridin, there are two tetrahydroporphyrin groups and four [4Fe?4S]2+ clusters. To our surprise, we discovered that about 80% of the tetrahydroporphyrin groups, however, do not bind iron. |
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