The ferric uptake regulator of Pseudomonas aeruginosa has no essential cysteine residues and does not contain a structural zinc ion.

The ferric uptake regulator (Fur) of Pseudomonas aeruginosa was expressed in Escherichia coli in its native form and as a fusion to the maltose-binding protein (MBP). Fur from the MBP fusion bound to MBP after proteolytic cleavage, and the two could only be separated by partial unfolding. The refolded protein was in the same conformation as native protein (as judged by circular dichroism and fluorescence spectroscopies) and was fully active in DNA-binding assays.