Mutations of tyrosine 537 in the human estrogen receptor-alpha selectively alter the receptor's affinity for estradiol and the kinetics of the interaction.
Mutation of tyrosine 537 (Y537) of the human estrogen receptor-alpha (hERalpha) produces receptors having a range of constitutive activity, which suggests that this residue modulates the conformational changes of the receptor. We investigated the effect of several mutations at this position, to phenylalanine (Y537F), to serine (Y537S), and to glutamic acid (Y537E), on the hormone-binding properties of the receptor. The affinities of the wt, the Y537F mutant, and the Y537S mutant for estradiol were similar: K(a) = 2.2 +/- 0.2, 3.9 +/- 0.5, and 2.8 +/- 0.4 nM(-1), respectively. By contrast, the affinity of the Y537E mutant for estradiol was reduced 10-fold, K(a) = 0.2 +/- 0.1 nM(-1). All proteins bound [(3)H]estradiol with a positive cooperative mechanism (n(H) = 1.7-1.9), indicating they can form dimers. The wt receptor and the Y537S and Y537E mutants exhibited biphasic dissociation kinetics, which is also indicative of dimerization. Surprisingly, the half-lives of the slow component of the wt and the Y537E mutant were indistinguishable, 118 +/- 3.4 and 122 +/- 4.5 min, respectively, even though the affinity of the Y537E mutant for hormone was reduced 10-fold. The half-life of the slow component of the Y537S mutant was reduced to 96.5 +/- 3.8 min. Molecular models were constructed and compared to identify changes in the structure that correlate with the observed effects on hormone binding. Local alterations in hydrogen bonding, the position of side chains, and the position of the peptide backbone were observed. Taken together, these results show that mutations at Y537 selectively alter the affinity and kinetics of hormone binding to the receptor, and are consistent with the idea that the estradiol-estrogen receptor interaction can follow more than one pathway.
Zhong
L
L
Department of Physiology and Barbara Ann Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
Skafar
D F
DF
D000818:Animals; D002460:Cell Line; D018360:Crystallography, X-Ray; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000737:chemistry / Q000378:metabolism*; D047628:Estrogen Receptor alpha; D018698:Glutamic Acid / Q000737:chemistry; D006801:Humans; D006860:Hydrogen Bonding; D007313:Insecta; D007700:Kinetics; D008024:Ligands; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010455:Peptides / Q000737:chemistry; D010649:Phenylalanine / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D011960:Receptors, Estrogen / Q000235:genetics* / Q000502:physiology*; D012694:Serine / Q000737:chemistry; D013997:Time Factors; D014162:Transfection; D014443:Tyrosine / Q000737:chemistry*
D018076:DNA, Complementary; D047628:Estrogen Receptor alpha; D008024:Ligands; D010455:Peptides; D011960:Receptors, Estrogen; D018698:Glutamic Acid; D014443:Tyrosine; D012694:Serine; D010649:Phenylalanine; D004958:Estradiol