Cys92, Cys101, Cys197, and Cys203 are crucial residues for coordinating the iron-sulfur cluster of RhdA from Acidithiobacillus ferrooxidans.

By proteomic analysis, we found a rhodanese-like protein(RhdA) from Acidithiobacillus ferrooxidans ATCC 23270 whose C-terminal contained a cysteine motif (Cys-XX-Trp-XX-Cys), known to bind iron-sulfur clusters. But so far, there were no articles to confirm the existence of iron-sulfur cluster in RhdA. In this study, RhdA gene from A. ferrooxidans ATCC 23270 was cloned and expressed in Escherichia coli, the protein was purified by one-step affinity chromatography to homogeneity. The UV-Vis scanning and EPR spectra results indicated that the wild-type proteins contained an iron-sulfur cluster. Site-directed mutagenesis results revealed that the four cysteines Cys92, Cys101, Cys197, and Cys203 were crucial residues for iron-sulfur cluster binding.