Fuscoredoxin Novel Fe-S Cluster

A preliminaiy characterization of a new iron—sulfur protein isolated from Desulfovibrio vulgaris Hildenborough was reported in 1989 124). The protein contained approximately 6 iron and 6 inorganic sulfur atoms per molecule. The FPR spectrum of the dithionite reduced protein exhibited an S = signal similar to what was found for synthetic compounds with a [6Fe-6S] core (prismane core). No other FPR signals were reported at this time, and based on the observed similarity it was suggested that this peculiar iron-sulfur protein contained a [6Fe-6S] cluster. Because it had no known function, the pro- 

Finally, a disagreement was noted between the iron determination results, which showed the existence of only 5 to 8 iron atoms/mole-cule, and the above analysis. As a solution to this discrepancy, it was proposed that the samples could contain a mixture of holo- and apoprotein. 

Based on recently obtained crystallographic data, cluster I and II were renamed cluster 2 and 1, respectively. In the following discussion the new nomenclature will be used. 

Resonance Raman studies of the recombinant proteins showed vibrational bands at the 200-430 cm region characteristic of iron-sulfur clusters (124). Most interestingly, on Fe and O isotope sensitive band was detected at 801 cm which could be attributed to either a Fe(IV)=0 species or a monobridged Fe-O-Fe structure. This observation, together with Mossbauer analysis, which indicated a mixed N, 0, and S ligand environment for cluster 2, suggests a Fe-O-Fe or Fe=0 unit as part of the structure for cluster 2. 

The crystallographic structure of the D. vulgaris protein has been reported by Lindley and collaborators (132). The structure was solved to a resolution of 1.7 A. The major findings are consistent with most of the conclusions derived from the Mossbauer work done in the D. desulfuricans protein. The protein was found to contain two distinct clusters of the same nuclearity. Also, one cluster has a mixed N, O, S ligand environment, while the other has a regular iron-sulfur core 

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C. Cluster Stmcturrd Interconversions and S3mthesis of Heterometal Clusters Fuscoredoxin (Novel Fe-S Cluster)... 

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