Synthesis of high molecular weight thyroglobulin peptides by thyroid polysome in vitro

Cell-free protein synthesis: the state of the art

Cell-free protein synthesis harnesses the synthetic power of biology, programming the ribosomal translational machinery of the cell to create macromolecular products. Like PCR, which uses cellular replication machinery to create a DNA amplifier, cell-free protein synthesis is emerging as a transformative technology with broad applications in protein engineering, biopharmaceutical development, and post-genomic research. By breaking free from the constraints of cell-based systems, it takes the next step towards synthetic biology. Recent advances in reconstituted cell-free protein synthesis (Protein synthesis Using Recombinant Elements expression systems) are creating new opportunities to tailor the reactions for specialized applications including in vitro protein evolution, printing protein microarrays, isotopic labeling, and incorporating nonnatural amino acids.

Immunoelectron microscopic localization of thyroglobulin in the human thyroid gland

The microidentification of the organelles containing thyroglobulin (TG) in the follicular cells of human thyroid glands were studied by the immunoelectron microscopic method. Fresh human thyroid glands were used for the purification of TG. TG was purified by differential salt fractionation and DEAE-cellulose chromatography. Anti-human TG rabbit IgG antibody was obtained by immunization of this purified TG. F(ab')2 fragments of anti-TG rabbit IgG antibody were prepared by pepsin digestion. The specificity of the antibody was tested on an Ouchterlony immunodiffusion plate. Conjugation of the purified F(ab')2 fragments of anti-TG rabbit IgG antibody to horse radish peroxidase was performed in order to use the direct peroxidase labelled antibody method. Under immunohistochemical light microscopy, the luminal colloid and the follicular cells appeared heavily stained. Under immunoelectron microscopy, positive reactions were observed in the rough endoplasmic reticulum, the Golgi apparatus, and the apical cell border. To date, no clear direct evidence of the presence of TG in the rough endoplasmic reticulum and the Golgi apparatus of human thyroid cells has ever been reported in immunoelectron microscopic studies. This study indicates that the use of F(ab')2 fragments of anti-TG rabbit IgG antibody in immunoelectron microscopic study is useful for the identification of TG in organelles of human thyroid follicular cells.

Iodination of thyroglobulin. An intracellular or extracellular process?

The location in the thyroid follicle of the iodination of thyroglobulin has been a matter of debate for several decades. This problem is not a question of mere academic interest. Knowledge of the locus--or loci--of iodination is necessary for a full understanding of the mechanisms involved in thyroid-hormone synthesis and release. In the discussion about this problem 3 fundamentally different views have been--and still are--advocated. The first view implies that the site of iodination is the follicle lumen, the second that iodination is an intracellular process restricted to some organelle(s) in the follicle cells and the third that iodination occurs at the interface between the follicle cells and the follicle lumen. Below I will survey the major observations on which these different opinions are based and discuss the validity of the interpretations.