Iodination in relation to thyroglobulin maturation and subunit aggregation.

Noniodinated subunits of thyroglobulin can aggregate, but iodination of the aggregate is required for its stabilization (maturation). Rat-thyroid slices incorporate amino acids into subunits, but cannot form mature thyroglobulin from the newly synthesized subunits. This defect leads to an accumulation of 16S and 12S proteins, although the preexisting thyroglobulin is 19S. Accumulation of 16S and 12S proteins can be produced in rat thyroids by the administration to the animals of a thiocarbamide derivative, methimazole. Upon withdrawal of methimazole, iodination of the 16S and 12S proteins proceeds, and 19S protein appears.