title: Differences in nuclear thyroid hormone receptors among species.
abstract: Hepatic nuclear thyroid hormone receptors from rat, dog, chicken, and rainbow trout were compared. Receptor affinities for 3,5,3'-triiodo-L-thyronine (T3) were similar in preparations from rat, dog, and chicken, using isolated nuclei and nuclear extracts. Rainbow trout nuclear receptor showed a lower affinity for T3. Almost half of the receptors were released into the medium with rat and chicken nuclei, and 79.7 +/- 1.1% of the receptors were released with rainbow trout nuclei, when isolated nuclei were incubated with T3 at 22 degrees for 2 hr. The affinity constant of rat liver receptor for calf thymus DNA-cellulose at 0.17 M KCl, pH 7.4, was 3.98 +/- 1.47 x 10(5) M-1, when determined using DNA-cellulose columns. The number of salt bridges involved in DNA binding of the rat receptor was 5.73 +/- 0.38. When receptor-DNA interactions were compared among species, significant differences were found, but the receptors from dog and rainbow trout liver were similar. Sephacryl S-200 column chromatography showed that chicken receptor had a Stokes radius significantly smaller than that of rat receptor. Partial proteolysis of T3-receptor complex using trypsin alpha-chymotrypsin, elastase, and papain produced distinct T3-binding fragments in different species. Our data provide evidence that nuclear thyroid hormone receptors from different species have significant structural dissimilarities.
authors.affiliation: Department of Gerontology, Endocrinology, and Metabolism, Shinshu University School of Medicine, Matsumoto, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Ichikawa
authors.forename: K
authors.initials: K
authors.lastname: Hashizume
authors.forename: T
authors.initials: T
authors.lastname: Miyamoto
authors.forename: A
authors.initials: A
authors.lastname: Sakurai
authors.forename: K
authors.initials: K
authors.lastname: Yamauchi
authors.forename: Y
authors.initials: Y
authors.lastname: Nishii
authors.forename: T
authors.initials: T
authors.lastname: Yamada
mesh_terms: D000818:Animals; D002023:Bufo bufo / Q000502:physiology; D002645:Chickens / Q000502:physiology; D004247:DNA / Q000378:metabolism*; D004285:Dogs / Q000502:physiology; D008099:Liver / Q000032:analysis; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains / Q000502:physiology; D011988:Receptors, Thyroid Hormone / Q000032:analysis* / Q000378:metabolism; D013045:Species Specificity; D014284:Triiodothyronine / Q000378:metabolism*; D014337:Trout / Q000502:physiology; D014714:Vertebrates / Q000502:physiology*
chemical_list: D011988:Receptors, Thyroid Hormone; D014284:Triiodothyronine; D004247:DNA