EXAFS studies of the isolated bovine heart Rieske [2Fe-2S]1+(1+,2+) cluster

Recently the involvement of one or, more likely, two nitrogen-ligands in the Rieske-type [2Fe-2S] cluster has been reported based on the chemical assay and various spectroscopic analyses, such as EPR, Mössbauer, ENDOR, and resonance Raman, of isolated Thermus thermophilus HB-8 protein by Fee and his collaborators. Similarly, the presence of at least one nitrogen ligand was shown in the mitochondrial Rieske [2Fe-2S] cluster. We have conducted EXAFS studies of the Rieske [2Fe-2S] protein isolated from the cytochrome bc1 complex of bovine heart mitochondria. Standard analysis could not distinguish one or two nitrogen ligands per cluster. However, one nitrogen and three cysteine ligands per cluster was found to be, possibly, a better solution in more comprehensive analysis procedures.