Studies of double-labeled mouse thyrotropin and free alpha-subunits to estimate relative fucose content.
The composition and structure of the complex oligosaccharides of thyrotropin (TSH) and free alpha-subunits are not well established, but are believed to be important determinants of the biological properties of these glycoproteins. We employed a simple double-label technique to learn the relative fucose content of mouse thyrotropin and free alpha-subunits. Thyrotropic tumor minces were incubated simultaneously with [35S]methionine and [3H]fucose. Thyrotropin and free alpha-subunits were labeled with both isotopes, and the ratio of 3H/35S was higher in free alpha-subunits than in thyrotropin; free alpha-subunits were approximately fivefold richer in fucose than was thyrotropin. The 3H/35S ratio was not substantially altered in TSH or free alpha-subunits secreted after a brief incubation with 10(-7) M thyrotropin-releasing hormone. Species which incorporated [3H]fucose were resistant to endoglycosidase H. Thus, mouse free alpha-subunits secreted by thyrotropic tumor are relatively rich in fucose. Double-isotope labeling using an amino acid and a sugar appears to be a useful technique for studies of the glycoprotein hormones.
D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D005643:Fucose / Q000378:metabolism*; D015292:Glycoprotein Hormones, alpha Subunit; D051379:Mice; D010446:Peptide Fragments / Q000302:isolation & purification / Q000378:metabolism*; D010908:Pituitary Hormones, Anterior / Q000302:isolation & purification / Q000378:metabolism*; D013462:Sulfur Radioisotopes; D013972:Thyrotropin / Q000302:isolation & purification / Q000378:metabolism*; D014316:Tritium
D015292:Glycoprotein Hormones, alpha Subunit; D010446:Peptide Fragments; D010908:Pituitary Hormones, Anterior; D013462:Sulfur Radioisotopes; D014316:Tritium; D005643:Fucose; D013972:Thyrotropin