Vot. 127, No. 1, 1985 February 28, 1985 BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS Pages 37-43 "CROSS-LINKING WITH DIMETHYLSUBERIMIDATE TO STUDY THYROGLOBULIN CONFORMATION" * Bruno Di Jeso, Silvestro Formisano, and Giuseppe Palumbo Centre dl Endocrinologia ed Oncologia Sperimentale C.N.R. Dipartimento di Biologia e Patologia Cellulare e Moleeolare. Via S. Pansini, 5 80131 Naples, ITALY Received January 4, 1985 Summary - The present investigation demonstrates that the cross-linking agent, dimethylsuberlmidate, is an usefull tool to study thyroglobulln structure. In fact, while reproducible and discrete polymerization products are obtained in strictly controlled conditions, valuable information on the native assemblage of thyroglobulin subunits and the effects of its major post-translational modification (iodination) on its structure, are reported. ©1985Acad~icPress, Inc. Thyroglobulin is a large glycoprotein characterized by a sedimentation coefficient of 19 S. Two similar, probably identical subunits of 330,000 form the native molecule, which contains about 10% by weight of carbohydrates. A variable amount of iodine atoms are covalently linked to some tyrosine resi- dues forming mono and diiodotyrosines, which are the precursors of the thyroid hormones triiodothyronine (T3) and thyroxine (T4). The 330 KD subunit is one of the larger elementary chains known to be synthesized as a single polypepti- de (I). The assembly of the two 330,000 subunits into thyroglobulin occurs in two different ways: some are linked by weak interactions, therefore easily disso- ciable, whereas some others are covalently linked and can not be dissociated (2). The relative proportion of the undissociable fraction is positively correlated with the iodine content of thyroglobulin (3). It is not known wether the two types of interactions result in thyroglobulin molecules of different conformation; however, it has been claimed that the level of iodination causes thyroglobnlin to acquire different shapes (4). Address correspondence to Giuseppe Palumbo. Abbreviations used: DMS, dimethylsuberimidate; PAGE, polyacrylamide gel electrophoresis. SDS, sodium dodecylsulfate; 37 0006-29lX/85 $1.50 Copyright © 1985 by Academic Press, lnc. All rights of reproduction in any form reserved.