title: Hormone and DNA binding activity of a purified human thyroid hormone nuclear receptor expressed in Escherichia coli.
abstract: Using a T7 expression system, large amounts of the human placental c-erbA protein (h-TR beta 1) were expressed. From 1 liter of Escherichia coli culture, approximately 50-100 micrograms of purified h-TR beta 1 were obtained. Analysis of the binding data indicated that the purified h-TR beta 1 binds to 3,3',5-triiodo-L-thyronine (T3) with a Ka = 2.8 x 10(9) M-1. It binds to 3,3',5-triiodo-L-thyropropionic acid, 3,3',5-triiodo-L-thyroacetic acid, D-T3, L-thyroxine (T4), and 3',5',3-triiodo-L-thyronine with 475, 120, 39, 7, and 0.1%, respectively, of the activity of L-T3. This order of binding activity to T3 analogs is similar to that reported for the T3 nuclear receptor identified in tissues or cultured cells. Furthermore, the purified h-TR beta 1 binds to the T3 response element of the rat growth hormone gene. Thus, the purified h-TR beta 1 is active. To identify the hormone binding domain, the purified h-TR beta 1 was affinity labeled with underivatized [3',5'-125I]T4. A partial digestion by trypsin yielded a 125I-labeled 25-kDa fragment which was identified to be the domain Phe240-Asp456 by amino acid sequencing. Thus, the purified h-TR beta 1 appears suitable for other structural and functional studies.
authors.affiliation: Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: K H
authors.initials: KH
authors.lastname: Lin
authors.forename: T
authors.initials: T
authors.lastname: Fukuda
authors.forename: S Y
authors.initials: SY
authors.lastname: Cheng
mesh_terms: D001483:Base Sequence; D001667:Binding, Competitive; D002467:Cell Nucleus / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D007700:Kinetics; D008969:Molecular Sequence Data; D010957:Plasmids; D011988:Receptors, Thyroid Hormone / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D013963:Thyroid Hormones / Q000378:metabolism / Q000494:pharmacology; D014284:Triiodothyronine / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D011988:Receptors, Thyroid Hormone; D011994:Recombinant Proteins; D013963:Thyroid Hormones; D014284:Triiodothyronine