In vitro and in vivo iodination of human thyroglobulin in relation to hormone release

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Abstract
Reduced and S-alkylated thyroglobulin (Tgb) from different species were shown by SDS-PAGE to contain small peptides (from 45-9 kDA) rich in thyroxine. Several hypotheses were proposed to explain their origin. The polypeptide composition of iodine-poor (TgbA) and normally iodinated (Tgb B) human Tgb prepared by two different procedures (one minimizing and the other favoring post-mortem proteolysis) was compared in the native state and after in vitro iodination. Results show that one of the hormonogenic sites of human Tgb is part of a domain of the molecule most susceptible to proteolysis, especially when it is very iodinated.