BINDIG OF ESTRIOL BOVINESERUM ALBUMIN:DETERMINATION OF BINDING PARAMETERS AND CHARACTEREATlON OF BINDINGSITES

The binding of estriol, a female reproductive hormone, to bovine serum albumin (BSA) was studied by equilibrium dialysis (ED) method at 25°C and pH 7.4. Scatchard method of analysis showed that the binding of estriol has two sets of association constants: the high affinity association constant (k,) with low capacity (ni ) and low affinity association constant (k2) with high capacity (n2). Binding data of ED method suggested the presence of two high affinity binding sites with ki value of 1.54xl06 M'1 and ten low affinity binding sites with k2 value of 1.66xl05 M 1 at 25°C and pH 7.4. Site-specific probe displacement data suggested that estriol binds to site I, the warfarin site, with a higher affinity, while to site 11, the benzodiazepine site, with relatively lower affinity.