TY - JOUR
T1 - Inability of [3H]estriol to induce maximal cooperativity of the estrogen receptor
AU - Sasson, Shlomo
AU - Notides, Angelo C.
PY - 1984/4
Y1 - 1984/4
N2 - The interaction of [3H]estriol with the partially purified estrogen receptor from calf uterus shows positive cooperativity that is dependent upon receptor concentration and temperature. At a receptor concentration of 1 nM and 25°C the [3H]estriol-receptor cooperativity was low, the Hill coefficient (nH) was 1.03 ± 0.02; however, with increasing receptor concentrations the receptor's cooperativity increased until at approximately intracellular receptor concentration (20 nM) the nH = 1.20 ± 0.04. At 0°C and a receptor concentration of 10 nM the [3H]estriol-receptor interaction was highly cooperative, the Scatchard plot was convex and nH = 1.58 ±0.04 while at 30°C the Scatchard plot approached linearity and nH = 1.03 ± 0.02. In comparison, [3H]estradiol was capable of inducing, at 0 or 30°C and at a receptor concentration of 1 nM or greater, maximal receptor cooperativity, nH = 1.63. These data demonstrate: (a) the receptor's conformation and binding mechanism change in a specific manner with temperature, so that receptor analysis at 0°C does not necessarily reflect the receptor's properties at biologically relevant temperatures; (b) the dependence of the receptor's cooperativity on receptor concentration, which suggests interaction between dissociable subunits; and (c) the lower cooperativity induced by estriol, in comparison with estradiol, which indicates estriol is less efficient in shifting the receptor toward a higher affinity or the activated state of the receptor.
AB - The interaction of [3H]estriol with the partially purified estrogen receptor from calf uterus shows positive cooperativity that is dependent upon receptor concentration and temperature. At a receptor concentration of 1 nM and 25°C the [3H]estriol-receptor cooperativity was low, the Hill coefficient (nH) was 1.03 ± 0.02; however, with increasing receptor concentrations the receptor's cooperativity increased until at approximately intracellular receptor concentration (20 nM) the nH = 1.20 ± 0.04. At 0°C and a receptor concentration of 10 nM the [3H]estriol-receptor interaction was highly cooperative, the Scatchard plot was convex and nH = 1.58 ±0.04 while at 30°C the Scatchard plot approached linearity and nH = 1.03 ± 0.02. In comparison, [3H]estradiol was capable of inducing, at 0 or 30°C and at a receptor concentration of 1 nM or greater, maximal receptor cooperativity, nH = 1.63. These data demonstrate: (a) the receptor's conformation and binding mechanism change in a specific manner with temperature, so that receptor analysis at 0°C does not necessarily reflect the receptor's properties at biologically relevant temperatures; (b) the dependence of the receptor's cooperativity on receptor concentration, which suggests interaction between dissociable subunits; and (c) the lower cooperativity induced by estriol, in comparison with estradiol, which indicates estriol is less efficient in shifting the receptor toward a higher affinity or the activated state of the receptor.
UR - http://www.scopus.com/inward/record.url?scp=0021287681&partnerID=8YFLogxK
U2 - 10.1016/0022-4731(84)90014-1
DO - 10.1016/0022-4731(84)90014-1
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C2 - 6727347
AN - SCOPUS:0021287681
SN - 0022-4731
VL - 20
SP - 1027
EP - 1032
JO - Journal of Steroid Biochemistry
JF - Journal of Steroid Biochemistry
IS - 4 PART 2
ER -