The Significance of Iodine in the Aggregation of Subunits Into Thyroglobulin and in the Formation of 27s Iodoprotein

Sinadinović, J; Jovanovic, M. J.; Kraincanić, M; Djurdjević, Dj.

doi:10.1530/acta.0.0730043

Cited by 8 publications

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“…Although we found a mean relative amount of S-TG similar to that earlier observed in normal rat thyroid glands (Smeds 1972b), the relative amount of S-TG in individual follicles demonstrated a large variation ranging from 10 -48% of the total protein amount. The physio¬ logical importance of the S-TG fraction and its variation between individual follicles is not known, but earlier investigations clearly show, that the iodination of thyroglobulin is crucial for the forma¬ tion of aggregates of thyroglobulin in the follicle lumen (Sinadinovic et al 1973;Frati et al 1974;Smeds & Anderberg 1977, 1978.…”

Section: Discussionmentioning

confidence: 99%

Protein composition in single follicles, homogenates and fine-needle aspiration biopsies from normal and diseased human thyroid

Anderberg

Eneström

Gillquist

et al. 1981

Acta Endocrinologica

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The protein composition of the thyroid colloid was analysed by microgel electrophoresis and densitometry in 41 euthyroid patients. The colloid samples were obtained from single follicles by micropuncture, from homogenates of microbiopsies or from aspiration biopsies. Fourteen of the patients had morphologically normal thyroid tissue, 18 had atoxic nodular goitre and 9 of the patients had atoxic adenoma. Ten of the patients with nodular goitre had prior to the investigation recieved lithium therapy for psychiatric disorders. The main component of the thyroid colloid was 19S thyroglobulin (TG), but larger iodoproteins (S-TG) and smaller protein fractions, an albumin-like protein and a pre-albumin fraction, were also present in varying relative amounts. Analyses of homogenates of microbiopsies from normal thyroid tissue demonstrated the same protein composition as observed in single follicles. In colloid samples from atoxic nodular goitre the lighter protein fractions were absent in most of the samples. Analyses of homogenates or aspiration biopsies could not demonstrate this alteration in the protein composition in nodular goitre. Lithium therapy resulted in a significantly lower amount of the lighter protein fractions but unchanged amounts of the globulin fractions in atoxic nodular goitre.In the atoxic adenomas the protein composition was heterogeneous. The major globulin fractions as well as the lighter protein fractions were present in the analyses of colloids and homogenates of microbiopsies. Aspiration biopsies from atoxic adenomas could not be used for analyses of the protein composition due to contamination with serum proteins. The thyroid gland is structurally divided into three main compartments, the follicular lumina contain¬ ing the colloid, the follicular epithelium and the interfollicular space with interstitial tissue and blood-and lymph-vessels. Analysis of colloid col¬ lected by micropuncture of single rat thyroid fol¬ licles has shown the presence of thyroglobulin, larger aggregates of thyroglobulin here designated S-TG and of albumin-like protein and pre-albumin in varying relative amounts (Smeds 1972b). Cellfractionating studies in animal experiments have shown that the exocytotic vesicles in the follicle cells contain thyroglobulin-like molecules, the halfmolecule of thyroglobulin (the 12S iodoprotein) and an albumin-like protein (Björkman et al. 1976). The dominant protein fraction in the extrafollicular tissue fluid is the albumin fraction (Smeds 1972a). In addition a2-macroglobulin and a num¬ ber of lighter proteins are present in a constant proportion as determined by microgel electrophoresis. The scope of interest in the present study was to analyse the protein composition of the colloid in thyroid follicles from normal and diseased human

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Section: Discussionmentioning

confidence: 99%

Protein composition in single follicles, homogenates and fine-needle aspiration biopsies from normal and diseased human thyroid

Anderberg

Eneström

Gillquist

et al. 1981

Acta Endocrinologica

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“…It was found that the human fetal thyroid has a low ability for the uptake of radioiodine until the end of gestation (Evans et al, 1967). It has been claimed that iodine favours the aggregation of Tg subunits (Sinadinovió et al, 1971) and that adequate Tg iodination is responsible for the conversion of the Tg 19 S to the 27 S iodoprotein (Sinadinovió et al, 1973;Frati et al, 1974) which occurs in the follicle lumen (Smeds et al, 1979). This paper deals with the investigations of soluble thyroid iodoproteins in human fetuses of different gestational ages, the Tg content in the gland and the relationship of Tg with other thyroid proteins, as well as their correlation with the morphogenesis and maturation of the follicles in the fetal thyroid gland.…”

Section: Introductionmentioning

confidence: 99%

Some Characteristics of Soluble Thyroid Proteins in Human Fetus during Morphogenesis of Follicular Structure

Sinadinović¹,

Savin²,

Micić³

2009

Exp Clin Endocrinol Diabetes

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“…Thyroglobulin (Tgb) with a low iodine content unfolds or disaggregates into 12 S subunits more readily in the presence of mild dissociating agents than does normally iodinated Tgb (Lissitzky et al 1964Sellin Sc Goldberg 1965;Simon et al 1966;Ui Sc Tarutani 1968;Tantiemi Sc Ui 1969a;Andreoli et al 1969;Rolland 8c Lissitzky 1970;Sinadinovic et al 1973). This decreased stability has been demonstrated in the thyroglobulin of intact iodine-deficient animals (Inoue 8c Taurog 1968e,· Tarutani 8c Ui \9&9b; Rossi et al 1973) and in that of hypophysectomized iodine-replete animals (Rosenberg Se Cavalieri 1969Cavalieri et al 1970) in which the capacity of the thyroid to iodinate Tgb substrate is limited.…”

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confidence: 99%

The Relative Roles of Iodination and Iodothyronine Content on Thyroglobulin Stability

Fukuda

Greer

1975

Acta Endocrinologica

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We have independently varied the degree of iodination and of iodothyronine formation over a wide range by acutely administering various doses of perchlorate and/or methimazole to severely iodine-deficient rats 30 min before giving 131I\m=-\with graded quantities (1\p=n-\100 \ g=m\ gof 127I\m=-\). Thyroids were removed 4 h later and the soluble protein analyzed for labelled iodoamino acid composition and with sucrose density gradient ultracentrifugation. Since the total thyroid iodine content before administering 127I\m=-\was less than 1 \g=m\g, calculation of the degree of iodination and iodothyronine content of the labelled Tgb could be made from the known specificity of the injected labelled iodide. Newly organified iodine ranged from < 0.1 to 1.4 \g=m\g/thyroidand labelled iodothyronines from < 5 to 962 pmoles/thyroid. Both the degree of iodination and iodothyronine content varied directly with Tgb stability in the absence of inhibitors. But when Tgb iodination was kept constant, Tgb stability at pH 10.1 varied directly with iodothyronine content. When iodothyronine content was kept constant, Tgb stability was independent of the degree of iodination. Correlation of stability with iodothyronine content was highly significant (r = 0.79, P < 0.001) but not of stability with iodine content (r = 0.49, P > 0.05). We conclude that the primary determinant of Tgb stability in mild alkali is the iodothyronine content and not the degree of iodination of the protein. The increased Tgb stability may be induced by coupling between iodotyrosil residues of different 12 S subunits rather than between residues of the same 12 S subunit. Thyroglobulin (Tgb) with a low iodine content unfolds or disaggregates into 12 S subunits more readily in the presence of mild dissociating agents than does normally iodinated Tgb (Lissitzky et al Sinadinovic et al. 1973). This decreased stability has been demonstrated in the thyroglobulin of intact iodine-deficient animals (Inoue 8c Taurog 1968e,· Tarutani 8c Ui \9&9b; Rossi et al. 1973) and in that of hypophysectomized iodine-replete animals (Rosenberg Se Cavalieri 1969Cavalieri et al. 1970) in which the capacity of the thyroid to iodinate Tgb substrate is limited. In both these conditions, the formation of iodothyronines is also depressed. Therefore, the relative roles of degree of iodination and of iodothyronine content in determining Tgb stability is un¬ certain.Recent studies have indicated that increasing the iodothyronine content of preformed Tgb by giving TSH to iodine-deficient hypophysectomized rats whose intrathyroidal Tgb has been prelabelled with radioiodine. while pre¬ venting additional Tgb iodination through simultaneous administration of per¬ chlorate, is assocated with an increase in Tgb stability (Greer et al. 1971(Greer et al. , 1974.Our theory to explain these data is that during the coupling reaction there is a transfer of the phenolic group of one iodotyrosyl residue to an iodotyrosyl residue in an adjacent segment of peptide chain (which may be from either the same or a d...

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The Significance of Iodine in the Aggregation of Subunits Into Thyroglobulin and in the Formation of 27s Iodoprotein

Cited by 8 publications

References 0 publications

Protein composition in single follicles, homogenates and fine-needle aspiration biopsies from normal and diseased human thyroid

Protein composition in single follicles, homogenates and fine-needle aspiration biopsies from normal and diseased human thyroid

Some Characteristics of Soluble Thyroid Proteins in Human Fetus during Morphogenesis of Follicular Structure

The Relative Roles of Iodination and Iodothyronine Content on Thyroglobulin Stability

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