Glu43 is an essential residue for coordinating the [Fe₂S₂] cluster of IscR from Acidithiobacillus ferrooxidans

Abstract 

The iron–sulfur cluster regulator (IscR) was reported to be a repressor of the iscRSUA operon. In vitro transcription reactions revealed that the IscR had a repression effect on the iscR promoter. The IscR contains a [Fe₂S₂] cluster per each monomer, and three highly conserved cysteines were identified to ligate the [Fe₂S₂] cluster. It was proposed that a non-cysteine residue might be the fourth ligand for the [Fe₂S₂] cluster. In this study, using site-directed mutagenesis, Glu43 was found to be the fourth residue that coordinates the [Fe₂S₂] cluster of IscR.

Abbreviations: A. ferrooxidans, Acidithiobacillus ferrooxidans, IPTG, isopropyl-d-thiogalactopyranoside, IscA, iron–sulfur cluster assembly protein A, PAGE, polyacrylamide gel electrophoresis, PCR, polymerase chain reaction, SDS, sodium dodecylsulfate, EPR, electronic paramagnetic resonance

Keywords: Purification, Iron–sulfur cluster, Mutation, Acidithiobacillus ferrooxidans