Identification of the ferroxidase centre of Escherichia coli bacterioferritin

1995 ◽  
Vol 312 (2) ◽  
pp. 385-392 ◽  
Author(s):  
N E Le Brun ◽  
S C Andrews ◽  
J R Guest ◽  
P M Harrison ◽  
G R Moore ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Metal Ion ◽  
Oxidation Mechanism ◽  
Site Directed Mutagenesis ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Dinuclear Iron ◽  
Ferroxidase Activity ◽  
A Site ◽  
R2 Subunit

The bacterioferritin (BFR) of Escherichia coli takes up iron in the ferrous form and stores it within its central cavity as a hydrated ferric oxide mineral. The mechanism by which oxidation of iron (II) occurs in BFR is largely unknown, but previous studies indicated that there is ferroxidase activity associated with a site capable of forming a dinuclear-iron centre within each subunit [Le Brun, Wilson, Andrews, Harrison, Guest, Thomson and Moore (1993) FEBS Lett. 333, 197-202]. We now report site-directed mutagenesis experiments based on a putative dinuclear-metal-ion-binding site located within the BFR subunit. The data reveal that this dinuclear-iron centre is located at a site within the four-alpha-helical bundle of each subunit of BFR, thus identified as the ferroxidase centre of BFR. The metal-bound form of the centre bears a remarkable similarity to the dinuclear-iron sites of the hydroxylase subunit of methane mono-oxygenase and the R2 subunit of ribonucleotide reductase. Details of how the dinuclear centre of BFR is involved in the oxidation mechanism were investigated by studying the inhibition of iron (II) oxidation by zinc (II) ions. Data indicate that zinc (II) ions bind at the ferroxidase centre of apo-BFR in preference to iron (II), resulting in a dramatic reduction in the rate of oxidation. The mechanism of iron (II) oxidation is discussed in the light of this and previous work.

Tb3+ luminescence studies of Escherichia coli glutamine synthetase provides metal ion binding constants.

1993 ◽  
Vol 51 (1-2) ◽  
pp. 170
Author(s):  
Luis P. Reynaldo ◽  
Toru Maruyama ◽  
William DeW. Horrocks ◽  
Joseph.J. Villafranca
Keyword(s):  
Escherichia Coli ◽  
Glutamine Synthetase ◽  
Metal Ion ◽  
Binding Constants ◽  
Ion Binding ◽  
Metal Ion Binding

Terbium(III) luminescence study of the spatial relationship of tryptophan residues to the two metal ion binding sites of Escherichia coli glutamine synthetase

Biochemistry ◽  
1991 ◽  
Vol 30 (14) ◽  
pp. 3417-3421 ◽  
Author(s):  
Linda S. McNemar ◽  
Wann Yin Lin ◽  
Charles D. Eads ◽  
William M. Atkins ◽  
Patrice Dombrosky ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Binding Sites ◽  
Metal Ion ◽  
Spatial Relationship ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Tryptophan Residues ◽  
Ion Binding Sites ◽  
Relationship Of ◽  
Metal Ion Binding Sites

scholarly journals Cobalt activation of Escherichia coli 5'-nucleotidase is due to zinc ion displacement at only one of two metal-ion-binding sites

2003 ◽  
Vol 372 (2) ◽  
pp. 625-630 ◽  
Author(s):  
Lyle McMILLEN ◽  
Ifor R. BEACHAM ◽  
Dennis M. BURNS
Keyword(s):  
Escherichia Coli ◽  
Binding Site ◽  
Binding Sites ◽  
Metal Ion ◽  
Ion Binding ◽  
Nucleotidase Activity ◽  
Metal Ion Binding ◽  
E Coli ◽  
Ion Binding Sites ◽  
Metal Ion Binding Sites

Escherichia coli 5′-nucleotidase activity is stimulated 30- to 50-fold in vitro by the addition of Co2+. Seven residues from conserved sequence motifs implicated in the catalytic and metal-ion-binding sites of E. coli 5′-nucleotidase (Asp41, His43, Asp84, His117, Glu118, His217 and His252) were selected for modification using site-directed mutagenesis of the cloned ushA gene. On the basis of comparative studies between the resultant mutant proteins and the wild-type enzyme, a model is proposed for E. coli 5′-nucleotidase in which a Co2+ ion may displace the Zn2+ ion at only one of two metal-ion-binding sites; the other metal-ion-binding site retains the Zn2+ ion already present. The studies reported herein suggest that displacement occurs at the metal-ion-binding site consisting of residues Asp84, Asn116, His217 and His252, leading to the observed increase in 5′-nucleotidase activity.

Photophysical Characterisation, Metal Ion Binding and Enantiomeric Recognition of Chiral Ligands Containing Phenazine Fluorophore

2004 ◽  
Vol 69 (4) ◽  
pp. 885-896 ◽  
Author(s):  
Luisa Stella Dolci ◽  
Péter Huszthy ◽  
Erika Samu ◽  
Marco Montalti ◽  
Luca Prodi ◽  
...  
Keyword(s):  
Metal Ion ◽  
Photophysical Properties ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Ammonium Ions ◽  
Enantiomerically Pure ◽  
Binding Process ◽  
High Affinity ◽  
Enantiomeric Recognition ◽  
Chiral Species

Enantiomerically pure dimethyl- and diisobutyl-substituted phenazino-18-crown-6 ligands bind metal and ammonium ions and also primary aralkylammonium perchlorates in acetonitrile with high affinity, causing pronounced changes in their luminescence properties. In addition, they show enantioselectivity towards chiral primary aralkylammonium perchlorates. The possibility to monitor the binding process by photoluminescence spectroscopy can gain ground for the design of very efficient enantioselective chemosensors for chiral species. The observed changes in the photophysical properties are also an important tool for understanding the interactions present in the adduct.

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