The subunit structure of thyroglobulin.
Ontology highlight
ABSTRACT:
SUBMITTER: Pitt-Rivers R
PROVIDER: S-EPMC1163919 | biostudies-other | 1976 Sep
REPOSITORIES: biostudies-other
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Project description:Thyroglobulin (TG) is the protein precursor of thyroid hormones, which are essential for growth, development and the control of metabolism in vertebrates1,2. Hormone synthesis from TG occurs in the thyroid gland via the iodination and coupling of pairs of tyrosines, and is completed by TG proteolysis3. Tyrosine proximity within TG is thought to enable the coupling reaction but hormonogenic tyrosines have not been clearly identified, and the lack of a three-dimensional structure of TG has prevented mechanistic understanding4. Here we present the structure of full-length human thyroglobulin at a resolution of approximately 3.5 Å, determined by cryo-electron microscopy. We identified all of the hormonogenic tyrosine pairs in the structure, and verified them using site-directed mutagenesis and in vitro hormone-production assays using human TG expressed in HEK293T cells. Our analysis revealed that the proximity, flexibility and solvent exposure of the tyrosines are the key characteristics of hormonogenic sites. We transferred the reaction sites from TG to an engineered tyrosine donor-acceptor pair in the unrelated bacterial maltose-binding protein (MBP), which yielded hormone production with an efficiency comparable to that of TG. Our study provides a framework to further understand the production and regulation of thyroid hormones.
| S-EPMC7170718 | biostudies-literature
Project description:Thyroid hormones T3 and T4 play a crucial role in the regulation of vertebrate metabolism. The thyroglobulin (Tg) protein is key to thyroid hormone synthesis, and its structure is conserved among vertebrates. TgG is delivered through the secretory pathway to the lumen of the thyroid gland, where it is iodinated at specific tyrosine sites to form mono- or di-iodotyrosine, which combine to produce T3 and T4, respectively. The formation of these hormones depends on the precise 3D structure of thyroglobulin, which has remained unknown despite decades of research on this protein. Here, we present the cryo-electron microscopy structure of human thyroglobulin, to a global resolution of 3.2 Å. Our results offer structural insight into thyroid hormonogenesis and provide a framework to understand hundreds of clinically relevant mutations. The structure of hTg contributes to a better understanding and potentially improved treatment of thyroid hypothyroidism, thyroid cancer and other Tg disorders.
2022-02-24 | PXD018452 | Pride
Project description:The thyroglobulin (TG) protein is essential to thyroid hormone synthesis, plays a vital role in the regulation of metabolism, development and growth and serves as intraglandular iodine storage. Its architecture is conserved among vertebrates. Synthesis of triiodothyronine (T3) and thyroxine (T4) hormones depends on the conformation, iodination and post-translational modification of TG. Although structural information is available on recombinant and deglycosylated endogenous human thyroglobulin (hTG) from patients with goiters, the structure of native, fully glycosylated hTG remained unknown. Here, we present the cryo-electron microscopy structure of native and fully glycosylated hTG from healthy thyroid glands to 3.2 Å resolution. The structure provides detailed information on hormonogenic and glycosylation sites. We employ liquid chromatography-mass spectrometry (LC-MS) to validate these findings as well as other post-translational modifications and proteolytic cleavage sites. Our results offer insights into thyroid hormonogenesis of native hTG and provide a fundamental understanding of clinically relevant mutations.
| S-EPMC8748809 | biostudies-literature
Project description:Thyroglobulin is a homodimeric glycoprotein that is essential for the generation of thyroid hormones in vertebrates. Upon secretion into the lumen of follicles in the thyroid gland, tyrosine residues within the protein become iodinated to produce monoiodotyrosine (MIT) and diiodotyrosine (DIT). A subset of evolutionarily conserved pairs of DIT (and MIT) residues can then engage in oxidative coupling reactions that yield either thyroxine (T4; produced from coupling of a DIT `acceptor' with a DIT `donor') or triiodothyronine (T3; produced from coupling of a DIT acceptor with an MIT donor). Although multiple iodotyrosine residues have been identified as potential donors and acceptors, the specificity and structural context of the pairings (i.e. which donor is paired with which acceptor) have remained unclear. Here, single-particle cryogenic electron microscopy (cryoEM) was used to generate a high-resolution reconstruction of bovine thyroglobulin (2.3 Å resolution in the core region and 2.6 Å overall), allowing the structural characterization of two post-reaction acceptor-donor pairs as well as tyrosine residues modified as MIT and DIT. A substantial spatial separation between donor Tyr149 and acceptor Tyr24 was observed, suggesting that for thyroxine synthesis significant peptide motion is required for coupling at the evolutionarily conserved thyroglobulin amino-terminus.
| S-EPMC8561740 | biostudies-literature
Project description:Thyroglobulin protein is the precursor of thyroid hormones, which are essential for growth, development and control of metabolism in vertebrates. Hormone synthesis from thyroglobulin (TG) occurs in the thyroid gland via the iodination and subsequent coupling of pairs of tyrosine amino acids, whose positions in TG have not been clearly identified. Tyrosine proximity within TG is thought to enable the coupling reactions but the lack of a three-dimensional structure of TG has prevented mechanistic understanding. Here we determined the structure of full-length human thyroglobulin at ~3.4 Å resolution by cryo-electron microscopy (cryo-EM). To enable perturbation experiments we expressed human TG in human HEK cells and showed it to be active in hormone production. We identified all hormogenic tyrosine pairs in the structure and verified them via site-directed mutagenesis and in vitro hormone production assays. Analysis revealed that proximity, flexibility and solvent exposure of the tyrosines are key characteristics of the hormogenic sites. To support the validity of our insights, we engineered the small bacterial protein MBP (maltose binding protein) to produce thyroid hormones with similar efficiency as TG. Finally, our study provides an essential framework to further understand the production and regulation of thyroid hormones, including in thyroid diseases.
2020-02-06 | PXD014821 | Pride
Project description:The Tthyroglobulin (Tg) protein is the essential fundament toto thyroid hormone synthesis, a key player playing a vital role in the regulation of metabolism, development and growth and serving as intraglandular iodine storage. Its structure is conserved among vertebrates. Tg is delivered through the secretory pathway of the thyroid follicular unit to the central colloid depository, where it is iodinated at specific tyrosine sites to form mono- or diiodotyrosine, which combine to produce triiodothyronine (T3) and thyroxine (T4), respectively. Synthesis of these hormones depends on the precise 3D structure, iodination capacity and post-translational modification of Tg. The Tg structure is overall conserved among vertebrates and , which and structural information has long been remained unknown missing despite decades of research until recently structural information has been made available on human thyroglobulin (hTg) originating from recombinant hTg and endogenous hTg from patients with goitres. Here, we present the cryo-electron microscopy structure of native and fully functional human thyroglobulin (hTg) originating from healthy human thyroid glands, to a global resolution of 3.2 Å. We used LC-MS experiments to The structure provides detailed information on the location of the hTg hormonogenic sites by revealing native iodination, and reveals the position as well as the role of many of its glycosylation sites and other post-translational modifications. Our results offer structural insights into thyroid hormonogenesis of natively functional hTg and provide a fundamental understanding of clinically relevant hTg mutations, which can improve treatment of thyroid diseases.
2022-02-17 | PXD029013 | Pride
Project description: Not available
| EMPIAR-10833 | biostudies-other
Project description:The unit A-type glycopeptides were purified from porcine thyroglobulin by Pronase digestion followed by chromatography on a DEAE-Sephadex A-25 column. These glycopeptides were separated into five fractions (UA-I, -II, -IV and -V) by Dowex 50W (X2) column chromatography. Fractions UA-I, -II, -III, -IV and -V were found to have the compositions (Man)9(GlcNAc)2-Asn, (Man)8(GlcNAc)2-Asn, (Man)7(GlcNAc)2-Asn, (Man)6(GlcNAc)2-Asn and (Man)5(GlcNAc)2-Asn respectively. The structures of these five fractions were investigated by the combination of exo- and endo-glycosidase digestions, methylation analysis. Smith periodate degradation and acetolysis. The results showed that fraction UA-V had the simplest structure: see formula in text. The larger glycopeptides (fractions UA-I, -II, -III and -IV) contained additional mannose residues alpha (1 leads to 2)-linked to the terminal mannose residues in the above core structure. These unit A-type glycopeptides appear to be biosynthetic intermediates that are to be processed to form complex-type glycopeptides (unit B-type sugar chains).
| S-EPMC1162942 | biostudies-other
Project description:The oligosaccharide fraction was obtained from porcine thyroglobulin by hydrazinolysis. Four fractions of unit B-type oligosaccharides were purified by successive chromatographies on columns of DEAE-cellulose and concanavalin A-Sepharose, and their structures were investigated by the combination of endo- and exo-glycosidase digestions, methylation analysis and Smith degradation. From the results of these studies, the structures of the unit B oligosaccharides were proposed to be as follows: see formula in text. Thus the glycoprotein was found to have triantennary and biantennary complex-type oligosaccharides as acidic sugar chains. Concerning the triantennary oligosaccharides, the following structural features were shown: (1) the sialic acid residues were not localized on certain specific branches but distributed on all three branches; (2) however, alpha (2 leads to 3)-linked sialic acid residues were exclusively located on the terminal of the branch arising from C-4 of the branching alpha-mannose residue, whereas alpha (2 leads to 6)-linked sialic acid residues occupied terminals of the other branches; (3) the outer branching alpha-mannose residue was attached to C-3 or C-6 of an inner branching beta-linked mannose residue, and both types were observed to exist.
| S-EPMC1162943 | biostudies-other
Project description:Thyroid hormones are essential regulators of metabolism, development, and growth. They are formed from pairs of iodinated tyrosine residues within the precursor thyroglobulin (TG), a 660-kDa homodimer of the thyroid gland, by an oxidative coupling reaction. Tyrosine pairs that give rise to thyroid hormones have been assigned within the structure of human TG, but the process of hormone formation is poorly understood. Here we report a ~3.3-Å cryo-EM structure of native bovine TG with nascent thyroid hormone formed at one of the predicted hormonogenic sites. Local structural rearrangements provide insight into mechanisms underlying thyroid hormone formation and stabilization.
| S-EPMC9061844 | biostudies-literature