Correlative Effects of Puromycin on131I Metabolism and Amino Acid Incorporation by Calf Thyroid Slices

Abstract

In an effort to determine whether the iodination of tyrosyl residues of thyroglobulin occurs before or after protein synthesis in the biogenesis of thyroid hormones, the effects of puromycin on the organification of iodide and on protein synthesis were compared in slices from calf thyroid glands in vitro. A concentration of 3×1O^-5M puromycin inhibited the incorporation of Lleucine- l-¹⁴C into thyroprotein, including thyroglobulin, almost completely, but had virtually no effect on the formation of proteinbound ¹³¹MIT and ^13lDIT. It is concluded that the iodination of tyrosine occurs within the matrix of the preformed thyroglobulin molecule. Higher concentrations of puromycin were found to have an inhibitory effect on the formation of protein-bound iodine similar to that of other compounds which inhibit organic binding of thyroidal iodide. (Endocrinology76: 295, 1965)