Nondissociable complexes between125I-labeled T3 (125I-T3) and plasma proteins were observed after incubation of125I-T3 with plasma diluted 200-fold with phosphate buffer. The formation of these complexes was enhanced in the presence of Cu2+ and flavin mononucleotide and inhibited by reducing agents such as propylthiouracil, thiosulfate, dithiothreitol, and glutathione. The125I-T3 protein complexes could be disrupted after digestion with pronase. T3 itself was identified as a constituent of the pronase digests by co-chromatography with authentic131I-T3 to a constant isotopic ratio across the T3 area. Since treatment with 0.2% sodium dodecylsulfate or 8M urea did not disrupt the complexes, the T3-protein bond appears to have some of the characteristics of a covalent bond between hormone and protein.
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Clinical Biochemistry
- Biochemistry, medical