Iron-sulfur cluster Sulfolobus

In summary, it appears that the protein has to adopt the correct fold before the Rieske cluster can be inserted. The correct folding will depend on the stability of the protein the Rieske protein from the thermoacidophilic archaebacterium Sulfolobus seems to be more stable than Rieske proteins from other bacteria so that the Rieske cluster can be inserted into the soluble form of the protein during expression with the help of the chaperonins. If the protein cannot adopt the correct fold, the result will be either no cluster or a distorted iron sulfur cluster, perhaps using the two cysteines that form the disulfide bridge in correctly assembled Rieske proteins. 

Zanc-containing ferredoxin is the most abundant ferredoxin in chemohetero-trophically grown Sulfolobus sp. strain and T. acidophilum. The types and spectroscopic properties of the iron-sulfur clusters and the isolated zinc center are very similar in archaeal zinc-containing ferredoxins (Table I). Zinc-containing ferredoxin from Sulfolobus sp. strain 7 (103 amino acids, 7 cysteines) contains one [3Fe-4S] cluster (cluster I) with a midpoint redox potential of —280 mV, one [4Fe-4S] cluster (cluster II) with a midpoint redox potential of —530 mV, and a tetragonal zinc center. j acidophilum zinc-containing ferredoxin... 

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