Ligand selectivity by seeking hydrophobicity in thyroid hormone receptor.
Selective therapeutics for nuclear receptors would revolutionize treatment for endocrine disease. Specific control of nuclear receptor activity is challenging because the internal cavities that bind hormones can be virtually identical. Only one highly selective hormone analog is known for the thyroid receptor, GC-24, an agonist for human thyroid hormone receptor beta. The compound differs from natural hormone in benzyl, substituting for an iodine atom in the 3' position. The benzyl is too large to fit into the enclosed pocket of the receptor. The crystal structure of human thyroid hormone receptor beta at 2.8-A resolution with GC-24 bound explains its agonist activity and unique isoform specificity. The benzyl of GC-24 is accommodated through shifts of 3-4 A in two helices. These helices are required for binding hormone and positioning the critical helix 12 at the C terminus. Despite these changes, the complex associates with coactivator as tightly as human thyroid hormone receptor bound to thyroid hormone and is fully active. Our data suggest that increased specificity of ligand recognition derives from creating a new hydrophobic cluster with ligand and protein components.
Borngraeber
Sabine
S
Department of Biochemistry/Biophysics, University of California, San Francisco, CA 94143-2240, USA.
Budny
Mary-Jane
MJ
Chiellini
Grazia
G
Cunha-Lima
Suzana T
ST
Togashi
Marie
M
Webb
Paul
P
Baxter
John D
JD
Scanlan
Thomas S
TS
Fletterick
Robert J
RJ
D000085:Acetates / Q000737:chemistry* / Q000378:metabolism; D001559:Benzhydryl Compounds / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D006801:Humans; D008024:Ligands; D008958:Models, Molecular; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011988:Receptors, Thyroid Hormone / Q000737:chemistry* / Q000378:metabolism*; D013329:Structure-Activity Relationship; D037042:Thyroid Hormone Receptors beta
D000085:Acetates; D001559:Benzhydryl Compounds; C483767:GC 24 compound; D008024:Ligands; D011988:Receptors, Thyroid Hormone; D037042:Thyroid Hormone Receptors beta