scholarly journals Activation of membrane-bound high-affinity calcium ion-sensitive adenosine triphosphatase of human erythrocytes by bivalent metal ions

1975 ◽  
Vol 147 (2) ◽  
pp. 359-361 ◽  
Author(s):  
H Pfleger ◽  
H U Wolf
Keyword(s):  
Metal Ions ◽  
Calcium Ion ◽  
Metal Ion ◽  
Adenosine Triphosphatase ◽  
Erythrocyte Membranes ◽  
Bivalent Metal ◽  
High Affinity ◽  
Human Erythrocyte Membranes ◽  
Bivalent Metal Ions ◽  
Membrane Bound

The Ca2+-sensitive ATPase (adenosine triphosphatase) of human erythrocyte membranes is activated, not only by Ca2+ ions, but also by a series of other bivalent metal ions including Sr2+, Ba2+, Mn2+, Ni2+, Co2+, Cd2+, Cu2+, Zn2+ and Pb2+. The degree of activation is dependent on the radius of the ion rather than on its nature, in contrast with the dissociation constant of the enzyme--metal ion complex.

Degradation of Perfluoropolyether Fluids With Metal Ions

1999 ◽  
Vol 121 (2) ◽  
pp. 348-351 ◽  
Author(s):  
Takashi Fukuchi
Keyword(s):  
Metal Ions ◽  
Reaction Mechanisms ◽  
Metal Ion ◽  
Chemical Degradation ◽  
Bivalent Metal ◽  
Ether Cleavage ◽  
Cleavage Process ◽  
Metal Atoms ◽  
Bivalent Metal Ions ◽  
Fomblin Z

Chemical degradation of lubricant fluids of perfluoropolyether (PFPE), such as Fomblin Z-DOL, Fomblin AM-2001, Fomblin Z-25, Demnum SP-3, and Demnum SA, with bivalent metal ions was examined. The respective reaction mechanisms involve an ether cleavage process which is caused by the coordination of metal ions with oxygen atoms in the main chains of the PFPE. Metal ions were evaluated for their ability to degrade the PFPE, and the results demonstrate that the ions ranking in terms of this ability is as follows: Cu2+ > Ni2+ > Co2+ > Fe2+ > Mn2+ > Mg2+. This trend can be explained by the ionization potentials of the metal atoms. For an identical metal ion, the Demnum lubricants showed a greater stability than the Fomblin lubricants.

scholarly journals Calcium ion-dependent p-nitrophenyl phosphate phosphatase activity and calcium ion-dependent adenosine triphosphatase activity from human erythrocyte membranes

1973 ◽  
Vol 136 (1) ◽  
pp. 185-194 ◽  
Author(s):  
Alcides F. Rega ◽  
Donaldo E. Richards ◽  
Patricio J. Garrahan
Keyword(s):  
Cell Membrane ◽  
Phosphatase Activity ◽  
Human Erythrocyte ◽  
Calcium Ion ◽  
Adenosine Triphosphatase ◽  
Erythrocyte Membranes ◽  
Dependent Atpase ◽  
Nitrophenyl Phosphate ◽  
Inner Surface ◽  
Human Erythrocyte Membranes

In the presence of ATP and of Mg2+, human erythrocyte membranes show a phosphatase activity towards p-nitrophenyl phosphate which is activated by low concentrations of Ca2+. The effect of Ca2+ is strongly enhanced if either K+ or Na+ is also present. Activation of the p-nitrophenyl phosphate phosphatase by Ca2+ reaches a half-maximum at about 8μm-Ca2+ and is apparent only when the ion has access to the inner surface of the cell membrane. Ca2+-dependent phosphatase activity can only be observed if ATP is at the inner surface of the cell membrane, and the presence of ATP seems to be absolutely necessary, since either its removal or its replacement by other nucleoside triphosphates abolishes the activating effect of Ca2+. The properties of the (ATP+Ca2+)-dependent phosphatase are very similar to those of the Ca2+-dependent ATPase (adenosine triphosphatase), also present in erythrocyte membranes, which probably is involved in Ca2+ transport in erythrocytes. The similarities suggest that both activities may be properties of the same molecular system. This view is further supported by the fact that p-nitrophenyl phosphate inhibits to a similar extent Ca2+-dependent ATPase activity and ATP-dependent Ca2+ extrusion from erythrocytes.

scholarly journals The specificity of yeast low-Km cyclic AMP phosphodiesterase towards free bivalent metal ions and the diastereoisomers of cyclic adenosine phosphorothioate

1985 ◽  
Vol 226 (3) ◽  
pp. 897-900 ◽  
Author(s):  
K Suoranta ◽  
J Londesborough
Keyword(s):  
Cyclic Amp ◽  
Metal Ions ◽  
Metal Ion ◽  
Relative Activity ◽  
Bivalent Metal ◽  
Cyclic Amp Phosphodiesterase ◽  
Bivalent Metal Ions

The relative activity of a zinc-containing cyclic AMP phosphodiesterase towards the (Sp)- compared with the (Rp)-diastereoisomer of cyclic adensine phosphorothioate varied with the identity of the free bivalent metal ion from more than 35 to 0.074 along the series Mg2+ greater than Mn2+ greater than Co2+ greater than Zn2+ greater than Cd2+, showing that this ion, and not the tightly bound zinc, bonds to the phosphorothioate moiety of the substrate.

scholarly journals The kinetics of bivalent metal ion dissociation from myosin subfragments

1986 ◽  
Vol 233 (1) ◽  
pp. 173-177 ◽  
Author(s):  
A J Bennett ◽  
C R Bagshaw
Keyword(s):  
Metal Ions ◽  
Rate Constant ◽  
Metal Ion ◽  
Specific Site ◽  
Ph Change ◽  
Bivalent Metal ◽  
Skeletal Muscle Myosin ◽  
Adductor Muscles ◽  
Bivalent Metal Ions ◽  
Muscle Myosin

Bivalent metal ions have multiple roles in subunit association and ATPase regulation in scallop adductor-muscle myosin. To help elucidate these functions, the rates of Ca2+ and Mg2+ dissociation from the non-specific high-affinity sites on the regulatory light chains were measured and compared with those of rabbit skeletal-muscle myosin subfragments. Ca2+ dissociation had a rate constant of about 0.7 s-1 in both species, as measured by the time course of the pH change on EDTA addition. Mg2+ dissociation had a rate constant of 0.05 s-1, as monitored by its displacement with the paramagnetic Mn2+ ion. It is concluded that the exchange between Ca2+ and Mg2+ at the non-specific site, on excitation of both skeletal and adductor muscles, is too slow to contribute to the activation itself. The release of bivalent metal ions from the non-specific site is, however, the first step in release of the scallop regulatory light chain (Bennett & Bagshaw (1986) Biochem. J. 233, 179-186). In scallop myosin additional specific sites are present, which can bind Ca2+ rapidly, to effect activation of the ATPase. In the course of this work, Ca2+ dissociation from EGTA was studied as a model system. This gave rates of 1 s-1 and 0.3 s-1 at pH 7.0 and pH 8.0 respectively.

scholarly journals Metal-ion-promoted binding of triazine dyes to proteins. The interaction of Cibacron Blue F3G-A with yeast hexokinase

1982 ◽  
Vol 205 (2) ◽  
pp. 453-456 ◽  
Author(s):  
P Hughes ◽  
R F Sherwood ◽  
C R Lowe
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Difference Spectroscopy ◽  
Bivalent Metal ◽  
Cibacron Blue ◽  
Transition Series ◽  
Bivalent Metal Ions ◽  
A Site ◽  
Active Site Region ◽  
Yeast Hexokinase

Bivalent metal ions, particularly Zn2+ and other members of the first-row transition series, promote irreversible inactivation of yeast hexokinase by Cibacron Blue F3G-A at a site competitive with both ATP and D-glucose. Difference spectroscopy indicates that the protein-dye dissociation constant is decreased from 250 micrometers in the absence of metal ions to less than 100 micrometers in the presence of appropriate concentrations of metal ions, with specificity displayed in the sequence of Zn2+ greater than Cu2+ greater than Ni2+ greater than Mn2+. Quantitative inactivation of yeast hexokinase leads to the incorporation of approx. 1 mol of Cibacron Blue F3G-A/mol of subunit of mol. wt. 51 000 in both the presence and the absence of metal ion. These results suggest the formation of a highly specific ternary complex involving enzyme, dye and metal ion at the active-site region of the enzyme, and correlate well with the known effects of metal ions in promoting the binding of hexokinase to immobilized Cibacron Blue F3G-A.

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.

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