Molecular basis for the subtype discrimination of the estrogen receptor-beta-selective ligand, diarylpropionitrile.
Although the two subtypes of the human estrogen receptor (ER), ERalpha and ERbeta, share only 56% amino acid sequence identity in their ligand binding domain (LBD), the residues that surround the ligand are nearly identical; nevertheless, subtype-selective ligands are known. To understand the molecular basis by which diarylpropionitrile (DPN), an ERbeta-selective ligand, is able to discriminate between the two ERs, we examined its activity on ER mutants and chimeric constructs generated by DNA shuffling. The N-terminal region of the ERbeta LBD (through helix 6) appears to be fully responsible for the ERbeta selectivity of DPN. In fact, a single ERalpha point mutation (L384M) was largely sufficient to switch the DPN response of this ER to that of the ERbeta type, but residues in helix 3 are also important in achieving the full ERbeta selectivity of DPN. Using molecular modeling, we found an energetically favorable fit for the S-DPN enantiomer in ERbeta, in which the proximal phenol mimics the A ring of estradiol, and the nitrile engages in stabilizing interactions with residues in the ligand-binding pocket of ERbeta. Our findings highlight that a limited number of critical interactions of DPN with the ERbeta ligand-binding pocket underlie its ER subtype-selective character.
Sun
Jun
J
Department of Molecular and Integrative Physiology, University of Illinois, Urbana, Illinois 61801, USA.
Baudry
Jerome
J
Katzenellenbogen
John A
JA
Katzenellenbogen
Benita S
BS
D000595:Amino Acid Sequence; D001665:Binding Sites; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D006801:Humans; D008024:Ligands; D008715:Methionine / Q000378:metabolism; D008958:Models, Molecular; D018716:Molecular Mimicry; D008969:Molecular Sequence Data; D009154:Mutation; D009570:Nitriles / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D011960:Receptors, Estrogen / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D013912:Threonine / Q000378:metabolism; D014407:Tumor Cells, Cultured
D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D008024:Ligands; D009570:Nitriles; D011960:Receptors, Estrogen; D011994:Recombinant Proteins; D013912:Threonine; D008715:Methionine