title: Glutamine synthetase induction in embryonic neural retina: immunochemical identification of polysomes involved in enzyme synthesis.
abstract: Glutamine synthetase (EC 6.3.1.2) in embryonic neural retina in culture is rapidly induced by hydrocortisone. Retina polysomes involved in translation of this enzyme were precipitated with a high degree of specificity by the gammaglobulin isolated from antiserum against the enzyme (anti-enzyme gammaglobulin). Using immunoprecipitation procedures, we determined that the amount of polysome-bound nascent enzyme was maximal in polysomes comprising 9-14 ribosomes and was about 3-fold higher in the induced than in the noninduced retina. Within this size group of polysomes, those comprising 11-13 ribosomes showed consistently greater binding of anti-enzyme [(125)I]gammaglobulin than of normal [(125)I]-gammaglobulin. This size of polysomes corresponds to that calculated for a monocistronic messenger RNA for the subunit of this enzyme, which has a molecular weight of 42,000. The application of immunochemical techniques to identification of templates for synthesis of an enzyme in embryonic cells that constitutes less than 1% of the total cellular proteins indicates the usefulness of this method for detailed studies on regulation of other quantitatively minor products significant in cell differentiation.
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D000937:Antigen-Antibody Reactions; D002247:Carbon Isotopes; D002458:Cell Fractionation; D002642:Chick Embryo; D046508:Culture Techniques; D004622:Embryo, Mammalian; D004790:Enzyme Induction; D005974:Glutamate-Ammonia Ligase / Q000032:analysis / Q000096:biosynthesis*; D006854:Hydrocortisone / Q000494:pharmacology; D007074:Immunoglobulin G; D007456:Iodine Isotopes; D011132:Polyribosomes / Q000032:analysis* / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis* / Q000378:metabolism; D011817:Rabbits / Q000276:immunology; D011863:Radioimmunoassay; D012160:Retina / Q000166:cytology / Q000201:enzymology*; D014316:Tritium
chemical_list: D000596:Amino Acids; D002247:Carbon Isotopes; D007074:Immunoglobulin G; D007456:Iodine Isotopes; D012333:RNA, Messenger; D014316:Tritium; D005974:Glutamate-Ammonia Ligase; D006854:Hydrocortisone