Crystal structure of theVibrio choleraeferric uptake regulator (Fur) reveals insights into metal co-ordination

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The ferric uptake regulator (Fur) is a metal-dependent DNA-binding protein that acts as both a repressor and an activator of numerous genes involved in maintaining iron homeostasis in bacteria. It has also been demonstrated inVibrio choleraethat Fur plays an additional role in pathogenesis, opening up the potential of Fur as a drug target for cholera. Here we present the crystal structure ofV. choleraeFur that reveals a very different orientation of the DNA-binding domains compared with that observed inPseudomonas aeruginosaFur. Each monomer of the dimeric Fur protein contains two metal binding sites occupied by zinc in the crystal structure. In theP. aeruginosastudy these were designated as the regulatory site (Zn1) and structural site (Zn2). ThisV. choleraeFur study, together with studies on Fur homologues and paralogues, suggests that in fact the Zn2 site is the regulatory iron binding site and the Zn1 site plays an auxiliary role. There is no evidence of metal binding to the cysteines that are conserved in many Fur homologues, includingEscherichia coliFur. An analysis of the metal binding properties shows thatV. choleraeFur can be activated by a range of divalent metals.

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