Amino acid sequence of the unique 3,5,3'-triiodothyronine-containing sequence from porcine thyroglobulin

A unique T3-containing peptide was isolated by chemical and enzyme treatments from pTgb of different iodine contents and microsequenced: Leu-Ala-Ser-Lys-Ser-T3. This site can also form T4 to a small extent. It contains all the T3 of the protein and presents a special susceptibility to proteolysis thus suggesting a likely mechanism to explain that the thyroid secretes T3 preferentially to T4 in vivo.