Structure of carbohydrate unit A or porcine thyroglobulin.
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ABSTRACT:
SUBMITTER: Tsuji T
PROVIDER: S-EPMC1162942 | biostudies-other | 1981 Jun
REPOSITORIES: biostudies-other
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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: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:1. Glycopeptides were isolated by gel filtration on Sephadex G-25 and Sephadex G-50 from a Pronase digest of porcine thyroglobulin. 2. Isolated glycopeptides were separated into five main fractions on a column of DEAE-Sephadex A-25. Of these fractions I to III were further purified by SE-Sephadex C-25 or DEAE-Sephadex A-25 column chromatography. Several of the purified glycopeptides were homogeneous on paper electrophoresis. 3. Based on the chemical composition and molecular weight of the fractionated glycopeptides, two distinct types of heterosaccharide chain were demonstrated. 4. One type of the heterosaccharide unit consisted of four to eight residues of mannose and two residues of glucosamine and had a molecular weight of 1000-1700. The other type of unit contained sialic acid, fucose and galactose in addition to mannose and glucosamine and had a molecular weight of about 3600. 5. Mild alkaline treatment of the glycopeptide did not result in the destruction of threonine and serine. 2-Acetamido-1-N-(4-l-aspartyl)-2-deoxy-beta-d-glucopyranosylamine was isolated from partial acid hydrolysates.
| S-EPMC1176972 | biostudies-other
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:Human and rat thyroglobulin were reduced and alkylated in aqueous alkaline conditions in the absence of denaturants; the product of reduction in both cases has been found to have mol.wt. about 165000, or one-quarter that of the native molecule.
| S-EPMC1163919 | biostudies-other
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