Binding of thyroid hormone by human erythrocyte cytosol proteins.
Gel filtration (G-100, 0.01 M Tris, pH 7.4) of post-100,000 x g supernatant from lysate of washed human erythrocytes (RBC) revealed 3 fractions (R-1, R-2, R-3) which bound labeled T3 and T4. Major peak R-2 emerged with the mehoglobin fraction (A560 nm) and binding by this fraction was partially dissociable; the dissociable site bound D-T4, but not tetraidothyroacetic acid or reverse T3. Non-dissociable binding characterized peaks R-1 and R-3. R-1, R-2, and R-3 were pronase-digestible and R-1 binding was acid-unstable (pH 6.8 vs. 7.4). Evidence developed herein and elsewhere indicates that hemoglobin, itself, accounts for the binding within fraction R-2. Intact RBCs maintained for 72 hr at 4C in buffer enriched with T3 or T4 showed progressive incorporation with time of iodothyronines into the hemoglobin fraction.
D002850:Chromatography, Gel; D003600:Cytosol / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D013696:Temperature; D013974:Thyroxine / Q000378:metabolism*; D013975:Thyroxine-Binding Proteins / Q000378:metabolism*; D014284:Triiodothyronine / Q000378:metabolism*
D013975:Thyroxine-Binding Proteins; D014284:Triiodothyronine; D013974:Thyroxine