Ultracentrifugal characterization of cytosol-binding proteins for thyroxine and triiodothyronine in human liver.
Sucrose density gradient ultracentrifugation was performed on human liver cytosol containing double tracers of 131I-thyroxine(T4) and 125I-triiodothyronine(T3) together with or without large amount of stable hormones. Tracer T4 bound to the cytosol indicated 2 peaks of 8.3S and 4.7S, both of which were displaced with stable T4, but not with T3. Maximal binding capacity of the 8.3S component averaged 43.2 microgram/100ml of 33% cytosol. Tracer T3 in the cytosol showed a single peak of 4.2S which was displaced with stable T3 and also with T4. The results indicate thtat the human liver cytosol contains limited-capacity binding proteins: the one specific for T4, and the other relatively specific for T3.
D002352:Carrier Proteins / Q000032:analysis* / Q000378:metabolism; D002499:Centrifugation, Density Gradient; D003600:Cytosol / Q000032:analysis* / Q000378:metabolism; D006801:Humans; D008099:Liver / Q000648:ultrastructure*; D013974:Thyroxine / Q000378:metabolism*; D014284:Triiodothyronine / Q000378:metabolism*
D002352:Carrier Proteins; D014284:Triiodothyronine; D013974:Thyroxine