title: The binding of a thyroid hormone metabolite, 3-monoiodo-L-thyronine, to bovine serum albumin as measured by circular dichroism.
abstract: The interaction between a thyroid hormone metabolite, 3-monoiodo-L-thyronine (3-T1) and bovine serum albumin (BSA) was investigated by using the CD method. An enhanced CD band was observed at the absorption wavelength region of 3-T1 around 293 nm suggesting the binding of 3-T1 to the BSA molecule. The ellipticity at 293 nm was measured at various molar ratios of 3-T1 to BSA, and the apparent binding constant and the maximum number of binding sites could be estimated as Kapp = 8.85 +/- 1.07 X 10(4) M-1 and n = 23.8 +/- 0.9 respectively. The CD of a mixture of BSA, 3-T1 and thyroxine (T4) was also studied at various pH's. The pH profile of the two characteristic CD bands at 293 nm and 320 nm, attributed to bound 3-T1 and T4, suggested that the optimum binding condition of 3-T1 was attained at alkaline pH of around 9, while that of T4 was attained over a wide pH range between 5-10. A significant role of the ionized 4'-hydroxyl group of 3-T1 in the binding reaction with BSA is also suggested.
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D002942:Circular Dichroism; D006863:Hydrogen-Ion Concentration; D011485:Protein Binding; D011487:Protein Conformation; D012710:Serum Albumin, Bovine / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet; D013970:Thyronines / Q000378:metabolism*
chemical_list: D013970:Thyronines; C013068:3-monoiodothyronine; D012710:Serum Albumin, Bovine