Properties of triiodothyronine-binding proteins in liver cytosol of rat.
The electrophoretic mobility and the sedimentation coefficient were determined in partially purified preparations of both rat liver cytosol and serum triiodothyronine (T3)-binding proteins. Crude cytosol and serum, each labeled with [125I]T3, were filtered through a Sephadex G-100 column. The cytosol yielded a single T3-binding peak, whereas three binding components were recognized in the serum. Protamine sulfate precipitated the cytosol T3-binding protein, but had no effect on the serum T3-binders. The cytosol protein and the three binding proteins from serum were analyzed by polyacrylamide gel electrophoresis and sucrose density gradient centrifugation. The cytosol binder migrated as a single peak on gel electrophoresis with an Rf of 0.53, whereas the serum proteins had RfS between 0.27-0.33. The sedimentation coefficient of the cytosol protein was 6.3 S, whereas it was 4.1 S for the major binding protein of the serum. These data indicate that: (i) preliminary purification by gel chromatography is a useful step for better characterization of the T3-binding proteins of the cytosol and serum; (ii) the cytosol binder is an acidic protein with completely different properties from those of the serum T3-binding proteins.
D000818:Animals; D002499:Centrifugation, Density Gradient; D002850:Chromatography, Gel; D003600:Cytosol / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D008099:Liver / Q000378:metabolism*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011988:Receptors, Thyroid Hormone
D011956:Receptors, Cell Surface; D011988:Receptors, Thyroid Hormone