title: The ferric uptake regulator of Pseudomonas aeruginosa has no essential cysteine residues and does not contain a structural zinc ion.
abstract: 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. As-prepared native Fur contained small amounts of Zn(2+) that were easily removed by treatment with EDTA, and apo-protein could be reconstituted with approximately one Zn(2+) ion per monomer. Thus, the P. aeruginosa Fur can probably accommodate a single Zn(2+) ion bound to the metal-sensing site. The single cysteine residue of P. aeruginosa Fur aligns with a cysteine in other members of the Fur family that is essential for activity of the E. coli protein, and is believed to provide one of the ligands to a structural Zn(2+) ion. This cysteine residue was shown to be dispensable for the in vivo activity of P. aeruginosa Fur, which is consistent with the suggestion that the P. aeruginosa protein does not contain a structural Zn(2+) ion. Members of the Fur family contain a highly conserved His-His-Asp-His motif. Alanine substitutions of residues in this motif showed His-87 and His-89 of P. aeruginosa Fur to be essential for activity, whilst His-86 and Asp-88 are partially dispensable.
authors.affiliation: School of Biological Sciences1 and School of Chemical Sciences2, University of East Anglia, Norwich NR4 7TJ, UK.
authors.forename: Allison C
authors.initials: AC
authors.lastname: Lewin
authors.affiliation: School of Biological Sciences1 and School of Chemical Sciences2, University of East Anglia, Norwich NR4 7TJ, UK.
authors.forename: Phillip A
authors.initials: PA
authors.lastname: Doughty
authors.affiliation: School of Biological Sciences1 and School of Chemical Sciences2, University of East Anglia, Norwich NR4 7TJ, UK.
authors.forename: Lynda
authors.initials: L
authors.lastname: Flegg
authors.affiliation: School of Biological Sciences1 and School of Chemical Sciences2, University of East Anglia, Norwich NR4 7TJ, UK.
authors.forename: Geoffrey R
authors.initials: GR
authors.lastname: Moore
authors.affiliation: School of Biological Sciences1 and School of Chemical Sciences2, University of East Anglia, Norwich NR4 7TJ, UK.
authors.forename: Stephen
authors.initials: S
authors.lastname: Spiro
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D002352:Carrier Proteins; D002942:Circular Dichroism; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics; D005290:Ferric Compounds / Q000737:chemistry*; D006639:Histidine / Q000378:metabolism; D058619:Maltose-Binding Proteins; D011487:Protein Conformation; D011550:Pseudomonas aeruginosa / Q000737:chemistry / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D015032:Zinc / Q000737:chemistry / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D005290:Ferric Compounds; D058619:Maltose-Binding Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; C068477:ferric uptake regulating proteins, bacterial; D006639:Histidine; D015032:Zinc; D003545:Cysteine