The Fe-uptake regulatory protein

The fur gene and its product were first identified, and have been best characterized, in E. coli, but homologs have also been found in a wide variety of other organisms [2, 8]. The relationships between metal binding, protein conformation and DNA binding remain very poorly understood. Fur binds ferrous iron, and the Fur-Fe + complex interacts with a characteristic, approximately 20-base pair, DNA sequence (the iron box ) in the promoter regions of Fur-repressed genes. Thus Fur, which is rich in histidine and cysteine residues, is an iron-responsive repressor of transcription. Other divalent metal cations, especially Mn + and Co +, mimic the effect of iron on Fur in both in vivo and in vitro experiments [8, 22, 23]. 

5 1 10 Major site has His N ligands, minor site has Cys S ligands [24, 28] 

Zn Not reported Not reported Binding detected by mass spectrometry, affinity columns and assays [23, 27] 

A total of 16-22 Cu + ions have been shown to bind relatively tightly to the 24-meric horse spleen apoferritin and to have a small catalytic effect on the aerobic oxidative uptake of Fe + [32], This observation is particularly surprising given that Zn + has an inhibitory effect on the oxidative uptake of Fe + by horse spleen apoferritin [33, 34]. As noted above, Zn + inhibits the ferroxidase activity of E. coli bacterioferritin by binding to the binuclear center [20, 21] and thus it was of some interest to investigate the effect that Cu has on the aerobic oxidative uptake of Fe + by , coli bacterioferritin. As described below, Cu + enhances the catalytic activity of bacterioferritin as far as Fe oxidation is concerned. 

3 Engineering catalytically active dimeric R. capsulatus bacterioferritin 

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