Zinc induced changes in the progesterone binding properties of the human endometrium

1980 ◽  
Vol 94 (1) ◽  
pp. 99-106 ◽  
Author(s):  
F. K. Habib ◽  
S. Q. Maddy ◽  
S. R. Stitch
Keyword(s):  
Receptor Binding ◽  
Binding Sites ◽  
Metal Ion ◽  
Protein Concentration ◽  
Zinc Concentration ◽  
Inhibitory Effect ◽  
Association Constants ◽  
Scatchard Analysis ◽  
Binding Properties ◽  
Induced Changes

Abstract. The binding of progesterone to plasma and endometrial cytosol is markedly influenced by Zn++, the degree and magnitude of this influence being dependent on the concentration of the metal ion. There is a critical protein concentration (approximately 10 mg/ml) beyond which the zinc exerts either a stimulatory or inhibitory effect. Maximum increases in binding of over 60% were attained in solutions of plasma containing 30 mg of protein whereas increases of 10% were measured in cytosol specimens with 10 mg protein/ml. This metal mediated effect was however progressively diminished with increasing zinc concentration resulting finally in the return of the binding to the levels observed in the absence of added Zn++. The zinc induced inhibition was most evident in plasma and cytosol with a protein concentration less than 10 mg/ml. The magnitude of this effect was inversely proportional to the levels of protein in solution. Scatchard analysis of the the data revealed that the number of progesterone bindings sites in the receptor are affected by the presence of the metal while the association constants remained unchanged. The study also suggests that the zinc induced changes are partially reversed by dithiothreitol and EDTA. We believe that the metal interferes directly with the SH groups at the receptor binding sites.

Characterization of Thromboxane A2/Prostaglandin H2 Receptors in Porcine Coronary Artery -The Inhibitory Effect of a Novel Dibenzoxepin Derivative, KW-3635

1992 ◽  
Vol 67 (05) ◽  
pp. 582-584 ◽  
Author(s):  
Ichiro Miki ◽  
Akio Ishii
Keyword(s):  
Coronary Artery ◽  
Binding Sites ◽  
Thromboxane A2 ◽  
Inhibitory Effect ◽  
Scatchard Analysis ◽  
Single Class ◽  
Porcine Coronary Artery ◽  
Equilibrium Binding ◽  
H2 Receptors

SummaryWe characterized the thromboxane A2/prostaglandin H2 receptors in porcine coronary artery. The binding of [3H]SQ 29,548, a thromboxane A2 antagonist, to coronary arterial membranes was saturable and displaceable. Scatchard analysis of equilibrium binding showed a single class of high affinity binding sites with a dissociation constant of 18.5 ±1.0 nM and the maximum binding of 80.7 ± 5.2 fmol/mg protein. [3H]SQ 29,548 binding was concentration-dependently inhibited by thromboxane A2 antagonists such as SQ 29,548, BM13505 and BM13177 or the thromboxane A2 agonists such as U46619 and U44069. KW-3635, a novel dibenzoxepin derivative, concentration-dependently inhibited the [3H]SQ 29,548 binding to thromboxane A2/prosta-glandin H2 receptors in coronary artery with an inhibition constant of 6.0 ± 0.69 nM (mean ± S.E.M.).

Binding of cadmium(II) and zinc(II) to human and dog serum albumins. An equilibrium dialysis and 113Cd-NMR study

1991 ◽  
Vol 69 (12) ◽  
pp. 809-820 ◽  
Author(s):  
William Goumakos ◽  
Jean-Pierre Laussac ◽  
Bibudhendra Sarkar
Keyword(s):  
Serum Albumin ◽  
Human Serum ◽  
Binding Sites ◽  
Metal Ion ◽  
Equilibrium Dialysis ◽  
Scatchard Analysis ◽  
Serum Albumins ◽  
High Affinity ◽  
Nmr Study ◽  
Nmr Techniques

The binding of Cd(II) and Zn(II) to human serum albumin (HSA) and dog serum albumin (DSA) has been studied by equilibrium dialysis and 113Cd(II)-NMR techniques at physiological pH. Scatchard analysis of the equilibrium dialysis data indicate the presence of at least two classes of binding sites for Cd(II) and Zn(II). On analysis of the high-affinity class of sites, HSA is shown to bind 2.08 ± 0.09 (log K = 5.3 ± 0.6) and 1.07 ± 0.12 (log K = 6.4 ± 0.8) moles of Cd(II) and Zn(II) per mole of protein, respectively. DSA bound 2.02 ± 0.19 (log K = 5.1 ± 0.8), and 1.06 ± 0.15 (log K = 6.0 ± 0.2) moles of Cd(II) and Zn(II) per mole of protein, respectively. Competition studies indicate the presence of one high-affinity Cd(II) site on both HSA and DSA that is not affected by Zn(II) or Cu(II), and one high-affinity Zn(II) site on both HSA and DSA that is not affected by Cd(II) or Cu(II). 113Cadmium-HSA spectra display three resonances corresponding to three different sites of complexation. In site I, Cd(II) is most probably coordinated to two or three histidyl residues, site II to one histidyl residue and three oxygen ligands (carboxylate), while for the most upfield site III, four oxygens are likely to be involved in the binding of the metal ion. The 113Cd(II)-DSA spectra display only two resonances corresponding to two different sites of complexation. The environment around Cd(II) at sites I and II on DSA is similar to sites I and II, respectively, on HSA. No additional resonances are observed in any of these experiments and in particular in the low field region where sulfur coordination occurs. Overall, our results are consistent with the proposal that the physiologically important high-affinity Zn(II) and Cd(II) binding sites of albumins are located not at the Cu(II)-specific NH2-terminal site, but at internal sites, involving mostly nitrogen and oxygen ligands and no sulphur ligand.Key words: albumin, human serum, dog serum, cadmium, zinc, copper, NMR, equilibrium dialysis, binding.

scholarly journals Unravelling the Structure of the Tetrahedral Metal-Binding Site in METP3 through an Experimental and Computational Approach

Molecules ◽  
2021 ◽  
Vol 26 (17) ◽  
pp. 5221
Author(s):  
Salvatore La Gatta ◽  
Linda Leone ◽  
Ornella Maglio ◽  
Maria De Fenza ◽  
Flavia Nastri ◽  
...  
Keyword(s):  
Metal Ions ◽  
Binding Site ◽  
Metal Binding ◽  
Binding Sites ◽  
Metal Ion ◽  
Structural Determinants ◽  
Binding Properties ◽  
Tetrahedral Geometry ◽  
Design Synthesis ◽  
Metal Binding Sites

Understanding the structural determinants for metal ion coordination in metalloproteins is a fundamental issue for designing metal binding sites with predetermined geometry and activity. In order to achieve this, we report in this paper the design, synthesis and metal binding properties of METP3, a homodimer made up of a small peptide, which self assembles in the presence of tetrahedrally coordinating metal ions. METP3 was obtained through a redesign approach, starting from the previously developed METP molecule. The undecapeptide sequence of METP, which dimerizes to house a Cys4 tetrahedral binding site, was redesigned in order to accommodate a Cys2His2 site. The binding properties of METP3 were determined toward different metal ions. Successful assembly of METP3 with Co(II), Zn(II) and Cd(II), in the expected 2:1 stoichiometry and tetrahedral geometry was proven by UV-visible spectroscopy. CD measurements on both the free and metal-bound forms revealed that the metal coordination drives the peptide chain to fold into a turned conformation. Finally, NMR data of the Zn(II)-METP3 complex, together with a retrostructural analysis of the Cys-X-X-His motif in metalloproteins, allowed us to define the model structure. All the results establish the suitability of the short METP sequence for accommodating tetrahedral metal binding sites, regardless of the first coordination ligands.

THE ROLE OF HEPARIN CHARGE DENSITY IN THE ANTITHROMBIN III-DEPENDENT AND ANTITHROMBIN III-INDEPENDENT INACTIVATION OF THROMBIN

1987 ◽  
Author(s):  
D Baruch ◽  
J Franssen ◽  
H C Hemker ◽  
T Lindhout
Keyword(s):  
Charge Density ◽  
Binding Sites ◽  
Antithrombin Iii ◽  
Inhibitory Effect ◽  
Structural Factors ◽  
Binding Properties ◽  
Platelet Factor ◽  
Factor Va ◽  
At Iii ◽  
Heparin Fractions

The dependence of the anticoagulant properties of heparin upon charge density may reflect structural factors that are important in anti-thrombin effect. We have previously demonstrated that in the absence of antithrombin III (AT III) unfractionated heparin inhibits the catalytic effect of thrombin upon platelet activation. In the present study we evaluated the thrombin-binding properties of heparin fractions obtained by ion-exchange chromatography on DEAE-Sephacei. We found that these fractions were able to bind to thrombin with an affinity that increased with their charge density. This was shown by their inhibitory effect in the absence of AT III on thrombin-catalyzed platelet factor Va formation and by the ability of active site blocked thrombin to prevent the heparin-dependent inactivation of thrombin by AT III. However, their increase in charge density and thus affinity for thrombin was found to go along with an increase in AT III-binding sites, as measured by the heparin-dependent increase of the intrinsic fluorescence of AT III. Moreover all heparin fractions showed the same specific antithrombin activity when the molar concentration of AT III-binding heparin was taken into account. We also investigated the thrombin-binding properties of two heparin fractions obtained by affinity chromatography on AT III-Sepharose. The AT III low affinity fraction was practically devoid of any inhibitory effect on the rate of the thrombin-catalyzed factor Va formation, indicating a low, if any, affinity for thrombin. In contrast the AT III-independent inhibition of thrombin was completely recovered from the AT III high affinity fraction. In addition, we also established that when the heparin fraction from the DEAE-Sephacel column, with the lowest charge density and very low in AT III binding material, was modified by the incorporation of sulfate groups so as to achieve a higher charge density, it obtained a higher affinity for thrombin but this modification caused the loss of half the AT III binding sites. In conclusion, it is apparent that fractionation of crude heparin on a DEAE-Sephacel column or on an AT III-Sepharose column does not result exclusively in a separation of either the thrombin-binding or the AT III-binding heparin fractions.

scholarly journals Characterization of Putative Virulence Factors of Pseudomonas aeruginosa Strain RBS Isolated from a Saltern, Tunisia: Effect of Metal Ion Cofactors on the Structure and the Activity of LasB

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
E. Rigane ◽  
R. Dutoit ◽  
S. Matthijs ◽  
N. Brandt ◽  
S. Flahaut ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Metal Ions ◽  
Virulence Factors ◽  
Binding Sites ◽  
Biofilm Formation ◽  
Metal Ion ◽  
Enzyme Stability ◽  
Inhibitory Effect ◽  
Ion Binding ◽  
Metal Ion Binding

Pseudomonas aeruginosa is a ubiquitous Gram-negative bacterium able to survive in diverse environments such as soil, plants, freshwater, and seawater. P. aeruginosa can be an opportunistic pathogen to humans when their immune system is deficient. Its pathogenicity may be linked to the production of virulence factors. We isolated P. aeruginosa strain RBS from the saltern of Sfax in Tunisia. In this study, we characterized the halotolerance, antibiotic susceptibility, and some virulence factors of strain RBS. High NaCl concentrations inhibited growth and motility. However, biofilm formation was enhanced to protect bacteria against salt stress. Among the 18 antibiotics tested, quinolones and tetracycline showed a significant inhibitory effect on growth, motility, and biofilm formation of strain RBS. β-Lactams, however, did not have any inhibitory effect on neither bacterial growth nor motility. In some cases, resistance was due, in part, to biofilm formation. We also showed that RBS produces two proteases, LasB and AprA, which have been shown to be implicated in host infection. LasB was further characterized to study the role of metal ions in enzyme stability. It possesses two distinct metal ion-binding sites coordinating a calcium and a zinc ion. The effect of metal ion chelation was evaluated as well as substitutions of residues involved in metal ion binding. Impairing metal ion binding of LasB led to a loss of activity and a sharp decrease of stability. Our findings suggest that the binding of both metal ions is interdependent as the two metal ions’ binding sites are linked via a hydrogen bond network.

Metal Ion Binding Properties of Perfluorosulfonate Membranes by Laser Excitation Spectroscopy

1988 ◽  
Vol 42 (2) ◽  
pp. 293-295 ◽  
Author(s):  
E. K. L. Wong ◽  
G. L. Richmond
Keyword(s):  
Metal Binding ◽  
Binding Sites ◽  
Metal Ion ◽  
Laser Excitation ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Binding Properties ◽  
Metal Binding Sites ◽  
Fluorescence Measurements ◽  
Experimental Parameters

The metal ion binding properties of the perfluorosulfonate membrane Nafion® have been investigated in this study. The experiments involve laser-induced fluorescence measurements of europium (III) ions which are bound to the membrane. By the exploitation of the hypersensitivity of the D → F transitions of europium (III) to the ligand binding environment, the properties of the metal binding sites have been analyzed as a function of various experimental parameters. The spectra and fluorescence lifetime measurements provide evidence for distinct metal binding sites within the polymer, each of which is sensitive to the conditions of the membrane preparation.

scholarly journals Calcium-binding properties of human erythrocyte calpain

1997 ◽  
Vol 325 (3) ◽  
pp. 721-726 ◽  
Author(s):  
Mauro MICHETTI ◽  
Franca SALAMINO ◽  
Roberto MINAFRA ◽  
Edon MELLONI ◽  
Sandro PONTREMOLI
Keyword(s):  
Active Site ◽  
Human Erythrocyte ◽  
Binding Sites ◽  
Calcium Binding ◽  
Metal Ion ◽  
Primary Event ◽  
Binding Properties ◽  
Physiological Concentration ◽  
Physiological Conditions ◽  
Sequential Mechanism

The results presented provide more information on the sequential mechanism that promotes the Ca2+-induced activation of human erythrocyte μ-calpain under physiological conditions. The primary event in this process corresponds to the binding of Ca2+ to eight interacting sites, of which there are four in each of the two calpain subunits. Progressive binding of this metal ion is linearly correlated with the dissociation of the proteinase, which reaches completion when all eight binding sites are occupied. The affinity for Ca2+ in the native heterodimeric calpain is increased 2-fold in the isolated 80 kDa catalytic subunit, but it reaches a Kd consistent with the physiological concentration of Ca2+ only in the active autoproteolytically derived 75 kDa form. Binding of Ca2+ in physiological conditions, and thus the formation of the 75 kDa subunit, can occur only in the presence of positive modulators. These are represented by the natural activator protein, found to be a Ca2+-binding protein, and by highly digestible substrates. The former produces a very large increase in the affinity of calpain for Ca2+, and the latter a smaller but still consistent decrease in the Kd of the proteinase for the metal ion. As a result, both dissociation into the constituent subunits and the autoproteolytic conversion of the native 80 kDa subunit into the active 75 kDa form can occur within the physiological fluctuations in Ca2+ concentration. The delay in the expression of the proteolytic activity with respect to Ca2+ binding to native calpain, no longer detectable in the 75 kDa form, can be attributed to a Ca2+-induced functional conformational change, which is correlated with the accessibility of the active site of the enzyme.

scholarly journals A New Thiourea Compound as Potential Ionophore for Metal Ion Sensor

2018 ◽  
Vol 18 (1) ◽  
pp. 116 ◽  
Author(s):  
Fatimatul Akma Awang Ngah ◽  
Emma Izzati Zakariah ◽  
Imran Fakhar ◽  
Nurul Izzaty Hassan ◽  
Lee Yook Heng ◽  
...  
Keyword(s):  
1H Nmr ◽  
Binding Sites ◽  
Metal Ion ◽  
Continuous Variation ◽  
Molar Ratio ◽  
Binding Properties ◽  
Binding Behavior ◽  
1H Nmr Titration ◽  
Guest Binding ◽  
Dissociation Constant Kd

A new thiourea compound, 2,2-oxybis(ethyl)-4-(1-naphthyl)-3-thiourea 3 has been synthesized and characterized by using FTIR, 1H-NMR, 13C-NMR, and MS spectroscopy. The binding properties of with various cations were also carried out using ‘naked eye’, UV-vis and 1H-NMR titration experiments. This compound exhibited effective binding for Hg2+ in the presence of other cations, such as Ag+, Ni2+, Sn2+, Zn2+, Fe2+, Cu2+, and Pb2+. Continuous variation titration experiments were conducted in order to determine the binding behavior for Hg2+. Stoichiometry of the host and guest binding interactions were also determined using continuous variation titration experiments and plotting molar-ratio curves. Pearson Product moment method was employed to calculate the correlation coefficient, and non-linear regression equation was used to calculate dissociation constant Kd. Molar-ratio and binding constant data substantiated the presence of binding sites for the compound 3.

scholarly journals Response of mouse proximal straight tubule and medullary thick ascending limb to beta-agonist.

1993 ◽  
Vol 4 (5) ◽  
pp. 1151-1158
Author(s):  
N S Morgunov ◽  
Y D You ◽  
D J Hirsch
Keyword(s):  
Receptor Binding ◽  
Binding Sites ◽  
Radioligand Binding ◽  
Beta Agonist ◽  
Scatchard Analysis ◽  
Thick Ascending Limb ◽  
Beta Receptor ◽  
Medullary Thick Ascending Limb ◽  
Binding Data ◽  
Straight Tubules

Scatchard analysis of (3H)CGP-12177 and (125I)cyanopindolol (CYP) radioligand binding data revealed the presence of specific beta-adrenergic receptor-binding sites on microdissected mouse proximal straight and medullary thick ascending limb (mTAL) tubules. beta-Receptor (10(-6) M isoproterenol) stimulation of isolated perfused mTAL tubules produced a consistent hyperpolarization of the transepithelial potential that was blocked by propranolol (10(-6) M), a beta-receptor antagonist, and furosemide (10(-4) M), an inhibitor of the Na+/K+/2 Cl- triporter. In contrast, there was no electrogenic response to isoproterenol stimulation in isolated perfused proximal straight tubules. In summary, radioligand binding data show that both proximal straight and mTAL tubules possess beta-receptor-binding sites. Electrogenic transport in the mTAL can be modulated by beta-agonists, but there was no detectable electrogenic response to beta-receptor stimulation in proximal straight tubules.

Sign in / Sign up

Export Citation Format

Share Document