scholarly journals The distribution of iron between the metal-binding sites of transferrin human serum

1980 ◽  
Vol 185 (2) ◽  
pp. 483-488 ◽  
Author(s):  
J Williams ◽  
K Moreton
Keyword(s):  
Human Serum ◽  
Metal Binding ◽  
Binding Sites ◽  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Iron Binding ◽  
Metal Binding Sites ◽  
Fresh Serum ◽  
Marked Preference ◽  
Terminal Site

The Makey & Seal [(1976) Biochim. Biophys. Acta 453, 250-256] method of polyacrylamide-gel electrophoresis in buffer containing 6 M-urea was used to determine the distribution of iron between the N-terminal and C-terminal iron-binding sites of transferrin in human serum. In fresh serum the two sites are unequally occupied; there is preferential occupation of the N-terminal site. On incubation of the serum at 37 degrees C the preference of iron for the N-terminal site becomes more marked. On storage of serum at −15 degrees C the iron distribution changes so that there is a marked preference for the C-terminal site. Dialysis of serum against buffer at pH 7.4 also causes iron to be bound much more strongly by the C-terminal than by the N-terminal site. The original preference for the N-terminal site can be resroted to the dialysed serum by addition of the diffusible fraction.

scholarly journals The effect of salt concentration on the iron-binding properties of human transferrin

1982 ◽  
Vol 201 (3) ◽  
pp. 527-532 ◽  
Author(s):  
J Williams ◽  
N D Chasteen ◽  
K Moreton
Keyword(s):  
Salt Concentration ◽  
Binding Sites ◽  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Iron Binding ◽  
Iron Release ◽  
Equilibrium Conditions ◽  
Binding Properties ◽  
Kinetics Of ◽  
Terminal Site

The salt dependence of the iron-binding properties of transferrin was studied by urea/polyacrylamide-gel electrophoresis. The distribution of iron between the N-terminal and C-terminal binding sites under equilibrium conditions and the rates of release of iron from the two sites were studied. It was found that salt increases the thermodynamic stability of iron binding in the N-terminal site relative to the C-terminal site. Similar behaviour is observed for the kinetics of iron release, where salt retards the rate of removal of iron from the N-terminal site but facilitates removal from the C-terminal site.

scholarly journals The iron-binding properties of hen ovotransferrin

1978 ◽  
Vol 173 (2) ◽  
pp. 533-539 ◽  
Author(s):  
J Williams ◽  
R W Evans ◽  
K Moreton
Keyword(s):  
Binding Sites ◽  
Gel Electrophoresis ◽  
Iron Binding ◽  
Alkaline Ph ◽  
Binding Properties ◽  
Partially Saturated ◽  
Isotope Method ◽  
Electrophoresis Method ◽  
Terminal Site ◽  
Double Isotope

1. The distribution of iron between the two iron-binding sites in partially saturated ovotransferrin was studied by labelling with 55Fe and 59Fe and by gel electrophoresis in a urea-containing buffer. 2. When iron is added in the form of chelate complexes at alkaline pH, binding occurs preferentially at the N-terminal binding site. In acid, binding occurs preferentially at the C-terminal site. 3. When simple iron donors (ferric and ferrous salts) are used the metal is distributed at random between the binding sites, as judged by the gel-electrophoresis method. The double-isotope method shows a preference of ferrous salts for the N-terminal site. 4. Quantitative treatment of the results of double-isotope labelling suggests that in the binding of iron to ovotransferrin at alkaline pH co-operative interactions between the sites occur. These interactions are apparently absent in the displacement of copper and in the binding of iron at acid pH.

scholarly journals The influence of pH on the equilibrium distribution of iron between the metal-binding sites of human transferrin

1981 ◽  
Vol 193 (3) ◽  
pp. 717-727 ◽  
Author(s):  
N D Chasteen ◽  
J Williams
Keyword(s):  
Metal Binding ◽  
Binding Sites ◽  
Equilibrium Distribution ◽  
Polyacrylamide Gel Electrophoresis ◽  
Ph Titration ◽  
Metal Binding Sites ◽  
Titration Curves ◽  
Diferric Transferrin ◽  
Differential Properties ◽  
Influence Of Ph

The dependence of the metal-binding properties of transferrin on pH in the pH 6–9 range was investigated by urea/polyacrylamide-gel electrophoresis. Equations are presented for calculating the relative values of the four conditional site constants for the stepwise binding of iron to the two sites of transferrin and for calculating the equilibrium distribution of the protein among the four principal forms, apotransferrin, the C-terminal and N-terminal monoferric transferrins and diferric transferrin. The relative affinity of iron for the two sites and the co-operativity of iron-binding follow characteristic ‘pH titration’ curves. A mathematical model that can account for the former behaviour is presented. In both cases the metal-binding sites are affected by the ionization of functional groups with apparent pKa values near physiological pH approx. 7.4. There is strong positive co-operatively in the release of protons from these groups. The results indicate that pH must be accurately controlled in studies of the differential properties of the two sites of the transferrin molecule.

scholarly journals Rational design of metal-binding sites in domain-swapped myoglobin dimers

2021 ◽  
Vol 217 ◽  
pp. 111374
Author(s):  
Satoshi Nagao ◽  
Ayaka Idomoto ◽  
Naoki Shibata ◽  
Yoshiki Higuchi ◽  
Shun Hirota
Keyword(s):  
Metal Binding ◽  
Binding Sites ◽  
Rational Design ◽  
Metal Binding Sites
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