Cooperativity and dimerization of recombinant human estrogen receptor hormone-binding domain.
The estrogen receptor dimerizes and exhibits cooperative ligand binding as part of its normal functioning. Interaction of the estrogen receptor with its ligands is mediated by a C-terminal hormone-binding domain (HBD), and residues within the HBD are thought to contribute to dimerization. To examine dimer interactions in the isolated HBD, a human estrogen receptor HBD fragment was expressed in high yield as a cleavable fusion protein in Escherichia coli. The isolated HBD peptide exhibited affinity for estradiol, ligand discrimination, and cooperative estradiol binding (Hill coefficient approximately 1.6) similar to the full-length protein. Circular dichroism spectroscopy suggests that the HBD contains significant amounts of alpha-helix ( approximately 60%) and some beta-strand ( approximately 7%) and that ligand binding induces little change in secondary structure. HBD dimer dissociation, measured using size exclusion chromatography, exhibited a half-life of approximately 1.2 h, which ligand binding increased approximately 3-fold (estradiol) to approximately 4-fold (4-hydroxytamoxifen). These results suggest that the isolated estrogen receptor HBD dimerizes and undergoes conformational changes associated with cooperative ligand binding in a manner comparable to the full-length protein, and that one effect of ligand binding is to alter the receptor dimer dissociation kinetics.
Brandt
M E
ME
Department of Physiology and Biophysics, University of California, Irvine, California 92697, USA. mdbrandt@uci.edu
Vickery
L E
LE
D000595:Amino Acid Sequence; D001665:Binding Sites / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D004967:Estrogens / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
D004967:Estrogens; D011960:Receptors, Estrogen; D011994:Recombinant Proteins