Rubredoxin, crystal structure determination

The iron-sulfur proteins, the ferredoxins, are so ubiquitous that it is difficult to realize that they were discovered only in the 1960s because of their unusual (at that time) g values. The simplest, rubredoxin, contains only one iron with the sulfur atoms of four cysteines supplying the ligation. Numerous others contain pairs of Fe atoms, and yet others contain 4Fe-4S cubes. The magnetic couplings between iron atoms leads to the unusual EPR g values, and a review by their discoverer is worthy of perusal. Iron and molybdenum XAS as well as EPR provided important clues to the structure of the cores of the nitrogenase enzyme prior to its X-ray crystal structure determination, as described in [26]. 

Although it has been known for more than two decades that the Rd-type metal centers can be easily reconstituted, there are very few structural data in the literature on metal-replaced rubredoxin-type centers. Recently, the crystal structure of the recombinant Zn-rubredoxin from C. pasteurianum [13] was determined by atomic resolution (1.2 A) and refined anisotropically. Preliminary data have also been reported for the Cd (Il)-substituted form of Rd from the same organism [54] but details about this structure have not yet been published. The NMR family of the Zn-substituted Rd from P. furiosus is also deposited in the Protein Data Bank... 

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