Reversible, positive cooperative interaction of 11β-chloromethyl-[3H]estradiol-17β with the calf uterine estrogen receptor

Shlomo Sasson*, John A. Katzenellenbooen

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

The binding of 11β-chloromethyl-[3H]estradiol-17β [3H]CME2) with the calf uterine estrogen receptor was investigated. The equilibrium binding analysis indicated a positive cooperative interaction yielding curvilinear Scatchard plots and Hill coefficients of 1.4-1.5. This positive cooperative interaction of [3H]CME2 was indistinguishable from the typical cooperative interaction of [3H]estradiol with the receptor. The apparent relative association constant and the relative binding affinity of CME2 for the estrogen receptor measured by competitive binding assay were 146 and 184%, respectively. The dissociation kinetics [3H]CME2 from the receptor was biphasic, composed of a fast dissociating component (15%, t 1 2 = 4 min at 0°C; 9%, t 1 2 = 4 at 28°C) and a slow dissociating component (85%,t 1 2 > 50 h at 0°C; 91 %, t 1 2 > 50 h at 28°C). The dissociation kinetics of [3H]estradiol was also biphasic: the t 1 2 of the fast dissociating component was 4 min at 0 and 28°C and ∼ 200 min for the slow dissociating component at both temperatures. The fraction of the slow [3H]estradiol dissociating component increased from 56 to 92% upon warming. Ethanol extraction and trichloroacetic acid treatment proved that the binding of [3H]CME2 is fully reversible. The unusual dissociation kinetics and the binding mechanism of CME; are discussed.

Original languageEnglish
Pages (from-to)859-865
Number of pages7
JournalJournal of Steroid Biochemistry
Volume33
Issue number5
DOIs
StatePublished - Nov 1989

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