Search PubMed⌕ Search

Biomedical subjects

S Lissitzky

Publications and source records attributed to S Lissitzky.

152 records · Page 9Linked to original sources
PubMedDate not supplied

Chemical composition of porcine thyroid cell plasma membranes.

Plasma membranes were isolated from thyroid cells obtained by trypsinization of porcine glands and maintained in culture conditions in the presence or absence of thyrotropin or dibutyryl cyclic AMP. The protein, phospholipid, cholesterol and sialic acid content of the 3 types of cell plasma membranes were very similar. High cholesterol and sialic acid content characterized these membranes. The amino acid and carbohydrate composition was similar to that shown for other eukaryotic plasma membranes. Sodium dodecylsulfate-polyacrylamide gel electrophoresis disclosed the presence of more than 20 protein bands, of which six corresponded to glycoproteins.

Amino Acids↗
PubMedDate not supplied

[Quaternary structure of thyroglobulin (author's transl)].

Porcine and ovine thyroglobulins were purified from fresh glands by slice extraciton, precipitation with buffered ammonium sulfate and Sepharose 6B gel filtration using 0.1 M sodium phosphate buffer pH 7.2 at all steps. In contrast to thyroglobulin obtained from frozen glands, the proteins purified from unfrozen glands only showed the 19 S and 12 S species by electrophoresis in sodium dodecylsulfate polyacrylamide gels. After full reduction and S-alkylation, no qualitative changes were observed in e gel electrophoresis patterns as compared to the unmodified proteins. Species of apparent molecular weight corresponding to the native 12 S subunit was the major component strongly suggesting a mol. wt. of about 330 000 for the elementary peptide chains of pig and sheep thyroglobulin. This was confirmed by sedimentation equilibrium analyses in 6 M guanidinium. HCl, 0.1 M sodium phosphate pH 7.2 OF FULLY REDUCED AND S-alkylated thyroglobulins which showed a weight average molecular weight of 310 000 daltons.

Animals↗
PubMedDate not supplied

[Biosynthesis and secretion of thyroglobulin (author's transl)].

Thyroglobulin (19 S, 660,000) (Tgb), the specific glycoprotein of the thyroid is the support of thyroid hormone biosynthesis. It is a dimer formed of 2 identical subunits (12 S, 330,000) containing a peptide chain of Mr 300,000 to which are associated through the asparagine of Asn-X-Thr (Ser) sequences, 2 types of carbohydrate units. The peptide chain is encoded in a 33 S mRNA of 8500 bases. The nature and number of Tgb genes, their transcription and the nuclear processing of premessenger RNA are unknown. However, the recent obtaining of clones of DNA complementary to Tgb mRNA will allow a rapid study of these structures and events. Tgb chains are synthesized on heavy polysomes associated with membranes of the endoplasmic reticulum. Nascent chains are then glycosylated by association of an oligosaccharide chain (GIcNAc)2 (Man)n (Glc)n' preassembled on a lipid carrier in the membrane, followed by removal of outer glucose and elongation in the Golgi membranes to produce branches of the type NeuNAc leads to Gal leads to GlcNAc. Possible roles for oligosaccharides in the structure and biosynthesis of Tgb are actively investigated. Then the fully glycosylated protein undergoes iodination that leads with a high yield to thyroid hormone formation according to a complex process critically depending upon the native 3-dimensional structure of the protein. Thyrotropin is likely to regulate Tgb production at the nuclear and cytoplasmic levels. Cell model systems for the study of Tgb biosynthesis and thyroid function are discussed.

Animals↗