Expression, purification and characterization of a high potential iron-sulfur protein from Acidithiobacillus ferrooxidans.

The high potential iron-sulfur protein (HiPIP) is involved in the iron respiratory electron transport chain of Acidithiobacillus ferrooxidans but its exact role is unclear. The gene of HiPIP from A. ferrooxidans ATCC 23270 was cloned and expressed in Escherichia coli, and the protein then purified by one-step affinity chromatography to homogeneity. The molecular mass of the HiPIP monomer was 7250.43 Da by MALDI-TOF MS, indicating the presence of the [Fe(4)S(4)] cluster. The optical and EPR spectra results of the recombinant protein confirmed that the iron-sulfur cluster was correctly inserted into the active site of the protein. Site-directed mutagenesis results revealed that Cys25, Cys28, Cys37 and Cys50 were involved in ligating to the iron-sulfur cluster.