title: Identification of poly G bound to thymidylate synthase.
abstract: Thymidylate synthase activity is increased in some methotrexate-resistant strains of Streptococcus faecium. The purified enzyme is associated with a polynucleotide which is not removed by dialysis. This polynucleotide contains one mole each of purine ribose and phosphate per mole base. Phosphate analyses after incubation with digestive enzymes indicate a tetranucleotide with one terminal phosphate. The constituent nucleosides are recovered quantitatively in a specific assay for guanosine. On HPLC, they are inseparable from authentic guanosine and the UV spectrum after HPLC is identical to that of guanosine. We conclude that poly G (GpGpGpGp) is bound to thymidylate synthase.
mesh_terms: D002851:Chromatography, High Pressure Liquid; D004351:Drug Resistance; D006151:Guanosine / Q000032:analysis; D008727:Methotrexate / Q000494:pharmacology; D010710:Phosphates / Q000032:analysis; D011068:Poly G / Q000378:metabolism*; D011131:Polyribonucleotides / Q000378:metabolism*; D012266:Ribose / Q000032:analysis; D013291:Streptococcus / Q000187:drug effects; D013940:Thymidylate Synthase / Q000378:metabolism*
chemical_list: D010710:Phosphates; D011131:Polyribonucleotides; D006151:Guanosine; D011068:Poly G; D012266:Ribose; D013940:Thymidylate Synthase; D008727:Methotrexate