scholarly journals The formation of ferritin from apoferritin. Inhibition and metal ion-binding studies

1973 ◽  
Vol 135 (4) ◽  
pp. 785-789 ◽  
Author(s):  
Ian G. Macara ◽  
Terence G. Hoy ◽  
Pauline M. Harrison
Keyword(s):  
Binding Site ◽  
Binding Sites ◽  
Iron Uptake ◽  
Metal Ion ◽  
External Surface ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Binding Studies ◽  
Titration Data ◽  
Substrate Concentrations

Inhibition by Zn2+of iron uptake by apoferritin at very low substrate concentrations is shown to be competitive. It is proposed that Zn2+competes with Fe2+for sites on the protein at which the oxidation of Fe2+is catalysed. Interpretation of titration data suggests there are two independent classes of binding site for Zn2+and several other cations. Sites in one such class are probably on the external surface of the apoferritin molecule. The catalytic binding sites are presumed to be internal and may involve histidine or possibly cysteine as ligands.

scholarly journals A enzima delta-aminolevullnato desidratase

1997 ◽  
Vol 19 (19) ◽  
pp. 201
Author(s):  
Tatiana Emanuelli
Keyword(s):  
Binding Site ◽  
Binding Sites ◽  
Metal Ion ◽  
Aminolevulinic Acid ◽  
Cysteine Residue ◽  
Ion Binding ◽  
Zinc Ions ◽  
Metal Ion Binding ◽  
Ion Binding Sites ◽  
Metal Ion Binding Sites

Delta-aminolevulinic acid dehydratase (ALA-D, EC 4.2.1.24) is a sulfhydryl-containing enzyme that asymetrically condenses two molecules of delta-aminolevulinic acid (ALA), catalyzing the formation of porphobilinogen, the monopyrrole precursor of ali biological tetrapyrroles (corrins, porphyrins, chlorins). The two ALA molecules have been termed Aside ALA and P-side ALA in reference to their fates as the acetyl and propionyl halves of the product. P-side ALA binds first and forms a Schiffbase with an active-site Iysine. ALA-D is a cytosolic enzyme present in mammals, plants, fungi and bacteria. Bovine enzyme has a molecular mass of 280 000 Da and is composed of eight similar subunits of 35 000 Da, but only four of the subunits form a Schiff-base with the substrate (half-site reactivity). ALA-D from all organisms requires a bivalent metal ion for activity. Although the considerable sequence conservation among ALA-D enzyme from various organisms, there are species-dependent differences in metal ion requirements for enzyme activity. ALA-D is a zinc-dependent enzyme in animals, yeast and some bacteria. Mammalian enzyme bounds 8 zinc ions/octamer. Bovine ALA-D contains two types of Zn2+ binding sites (A and B), each at a stoichiometry of four per octamer. A-metal-ion-binding sites, with a single cysteine residue among its ligands, bind the four zinc ions essential for ALA-D activity (catalytic zinc), which plays a role in A-side ALA binding, in inter-ALA bond formation and in product binding. B-metal-ion-binding sites, with four cysteine residues among its ligands, bind zinc ions refered to as structural, which seems to be involved in the protection of sulfhydryl groups from oxidation. An A-zinc-ion-binding site has been proposed to be present at a number of four per octamer on the enzyme from plants, but has not been demonstrated yet. ALA-D from plants contains two types of magnesium binding sites: four B-metal-ion-binding sites (bind magnesium essential for ALA-D activity) and eight C-metal-ion-binding sites (bind magnesium that activates the enzyme but is not essential for activity). The cysteine-rich sequence of mammalian ALA-D that presumably corresponds to the B-metalion-binding site is replaced by an aspartate-rich sequence in plant ALA-D, probably accounting for the difference on metal-ion requirement (Mg2+ instead of Zn2+ on B-metal-ion-binding site from plant ALA-D). E. coli ALA-D binds eight Zn2+ (presumably four at A-metal-ion-binding site and four at B-metalion-binding site) and eight Mg2+ (presumably at C-metal-ion-binding site) per octamer. Due to its sulfhydrilic nature ALA-D is inhibited by heavy metals such as lead and mercury, serving as a measure of metal intoxication. In addition the inhibition of this enzyme has been implicated with pathological changes observed in some types of porphyrias, hepatorenal tyrosinemia and after lead or mercury exposure. ALA-D inhibition may impair haeme biosynthesis and leads to ALA accumulation, which besides being a potent agonist of y-aminobutiric acid autoreceptors may act as a prooxidant.

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.

scholarly journals The src Homology 3-Like Domain of the Diphtheria Toxin Repressor (DtxR) Modulates Repressor Activation through Interaction with the Ancillary Metal Ion-Binding Site

2003 ◽  
Vol 185 (7) ◽  
pp. 2251-2258 ◽  
Author(s):  
John F. Love ◽  
Johanna C. vanderSpek ◽  
John R. Murphy
Keyword(s):  
Transition Metal ◽  
Binding Site ◽  
Diphtheria Toxin ◽  
Metal Ion ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Binding Studies ◽  
Transition Metal Ion ◽  
Diphtheria Toxin Repressor

ABSTRACT The diphtheria toxin repressor (DtxR) is a transition metal ion-activated repressor that acts as a global regulatory element in the control of iron-sensitive genes in Corynebacterium diphtheriae. We recently described (L. Sun, J. C. vanderSpek, and J. R. Murphy, Proc. Natl. Acad. Sci. USA 95:14985-14990, 1998) the isolation and in vivo characterization of a hyperactive mutant of DtxR, DtxR(E175K), that appeared to be constitutively active. We demonstrate here that while DtxR(E175K) remains active in vivo in the presence of 300 μM 2,2′dipyridyl, the purified repressor is, in fact, dependent upon low levels of transition metal ion to transit from the inactive apo form to the active metal ion-bound form of the repressor. Binding studies using 8-anilino-1-naphthalenesulfonic acid suggest that the E175K mutation stabilizes an intermediate of the molten-globule form of the repressor, increasing exposure of hydrophobic residues to solvent. We demonstrate that the hyperactive DtxR(E175K) phenotype is dependent upon an intact ancillary metal ion-binding site (site 1) of the repressor. These observations support the hypothesis that metal ion binding in the ancillary site facilitates the conversion of the inactive apo-repressor to its active, operator-binding conformation. Furthermore, these results support the hypothesis that the C-terminal src homology 3-like domain of DtxR plays an active role in the modulation of repressor activity.

The influence of metal-ion binding on the structure and surface composition of Sonic Hedgehog: a combined classical and hybrid QM/MM MD study

2016 ◽  
Vol 18 (32) ◽  
pp. 22254-22265 ◽  
Author(s):  
Manuel Hitzenberger ◽  
Thomas S. Hofer
Keyword(s):  
Metal Ions ◽  
Sonic Hedgehog ◽  
Binding Sites ◽  
Metal Ion ◽  
Surface Composition ◽  
Quantum Mechanical ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Structural Impact

The interaction of metal ions with Shh binding-sites and their structural impact are assessed via classical and quantum mechanical simulations.

scholarly journals Functional characterization of the dimerization domain of the ferric uptake regulator (Fur) of Pseudomonas aeruginosa

2006 ◽  
Vol 400 (3) ◽  
pp. 385-392 ◽  
Author(s):  
Erdeni Bai ◽  
Federico I. Rosell ◽  
Bao Lige ◽  
Marcia R. Mauk ◽  
Barbara Lelj-Garolla ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Metal Ions ◽  
Binding Site ◽  
Metal Ion ◽  
Association Constants ◽  
Ion Binding ◽  
Ferric Uptake Regulator ◽  
Metal Ion Binding ◽  
Dimerization Domain ◽  
High Affinity

The functional properties of the recombinant C-terminal dimerization domain of the Pseudomonas aeruginosa Fur (ferric uptake regulator) protein expressed in and purified from Escherichia coli have been evaluated. Sedimentation velocity measurements demonstrate that this domain is dimeric, and the UV CD spectrum is consistent with a secondary structure similar to that observed for the corresponding region of the crystallographically characterized wild-type protein. The thermal stability of the domain as determined by CD spectroscopy decreases significantly as pH is increased and increases significantly as metal ions are added. Potentiometric titrations (pH 6.5) establish that the domain possesses a high-affinity and a low-affinity binding site for metal ions. The high-affinity (sensory) binding site demonstrates association constants (KA) of 10(±7)×106, 5.7(±3)×106, 2.0(±2)×106 and 2.0(±3)×104 M−1 for Ni2+, Zn2+, Co2+ and Mn2+ respectively, while the low-affinity (structural) site exhibits association constants of 1.3(±2)×106, 3.2(±2)×104, 1.76(±1)×105 and 1.5(±2)×103 M−1 respectively for the same metal ions (pH 6.5, 300 mM NaCl, 25 °C). The stability of metal ion binding to the sensory site follows the Irving–Williams order, while metal ion binding to the partial sensory site present in the domain does not. Fluorescence experiments indicate that the quenching resulting from binding of Co2+ is reversed by subsequent titration with Zn2+. We conclude that the domain is a reasonable model for many properties of the full-length protein and is amenable to some analyses that the limited solubility of the full-length protein prevents.

Bromine substituted aminonaphthoquinones: synthesis, characterization, DFT and metal ion binding studies

RSC Advances ◽  
2016 ◽  
Vol 6 (91) ◽  
pp. 88010-88029 ◽  
Author(s):  
Gunjan Agarwal ◽  
Dipali N. Lande ◽  
Debamitra Chakrovarty ◽  
Shridhar P. Gejji ◽  
Prajakta Gosavi-Mirkute ◽  
...  
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Binding Studies

Bromine substituted aminonaphthoquinones – chemosensors for metal ions.

A conserved scaffold with heterogeneous metal ion binding site: the multifaceted example of HD-GYP proteins

2022 ◽  
Vol 450 ◽  
pp. 214228
Author(s):  
Francesca Cutruzzolà ◽  
Alessandro Paiardini ◽  
Chiara Scribani Rossi ◽  
Sharon Spizzichino ◽  
Alessio Paone ◽  
...  
Keyword(s):  
Binding Site ◽  
Metal Ion ◽  
Ion Binding ◽  
Metal Ion Binding
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