Kinetic analysis of the interaction of human estrogen receptor with an estrogen response element

Abstract

The kinetics of the interaction between recombinant human estrogen receptor and chicken vitellogenin gene II estrogen response element (ERE) were determined by ERE-Sepharose chromatography. The association constant of the interaction between the ERE and the human estrogen receptor was dependent on receptor concentration, estradiol binding and temperature. The highest association constant (80−100 × 10 6 M −1) was measured for the estradiol-bound receptor prepared at 25°C and at concentrations higher than 7 nM. At high receptor concentrations (> 7 nM) the binding mechanism of estradiol to the receptor was positive cooperative, indicating receptor homodimerization. At lower concentrations the binding mechanism was partially cooperative and the association constant of the liganded receptor was significantly lower. The binding mechanism at 4°C was cooperative as well, and the association constants were similarly dependent upon receptor concentration, but were 50% lower than the receptor prepared at 25°C. The association constant of the unliganded receptor was 4- to 5-fold lower than that of the liganded receptor at 25°C. These data suggest that in addition to estradiol-induced conformational changes in the receptor, the receptor dimers are subjected to temperature-dependent changes, which further increase their affinity for an ERE.