In vitro synthesis of the trifunctional protein, methylenetetrahydrofolate dehydrogenase--methenyltetrahydrofolate cyclohydrolase--formyltetrahydrofolate synthetase, in normal and transformed cells.
The trifunctional eucaryotic protein, methylenetetrahydrofolate dehydrogenase-methenyltetrahydrofolate cyclohydrolase-formyltetrahydrofolate synthetase, catalyzes three consecutive steps in the interconversion of folate derivatives which are required for thymidine and purine synthesis. The protein was synthesized in vitro using a reticulocyte lysate cell-free translation system. The immunoprecipitated translation product programmed by normal rat liver and rat brain mRNA was identical in size to that programmed by mRNA from transformed cells (HeLa, Morris hepatamas 5123D and 3924A). The protein synthesized by normal rat liver slices or Reuber H35 hepatoma cells in culture was similar in size to the translation product, suggesting that there is no significant posttranslational modification in vivo that alters the molecular weight. Differences in the level of synthesis were observed among the tissues examined. Since no consistent pattern emerged, however, it appears that transformation per se does not alter the structure or expression of this polypeptide. Nonetheless, a two- to three-fold increase in synthesis by Morris hepatoma 5123D may be an important biological observation with respect to studying the regulation of this protein that is critical for nucleotide synthesis.
D000619:Aminohydrolases / Q000096:biosynthesis*; D000818:Animals; D002478:Cells, Cultured; D005574:Formate-Tetrahydrofolate Ligase / Q000096:biosynthesis*; D066298:In Vitro Techniques; D008025:Ligases / Q000096:biosynthesis*; D008114:Liver Neoplasms, Experimental / Q000378:metabolism; D008297:Male; D045064:Methenyltetrahydrofolate Cyclohydrolase; D008754:Methylenetetrahydrofolate Dehydrogenase (NADP) / Q000096:biosynthesis*; D010088:Oxidoreductases / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013552:Swine
D012333:RNA, Messenger; D010088:Oxidoreductases; D008754:Methylenetetrahydrofolate Dehydrogenase (NADP); D000619:Aminohydrolases; D045064:Methenyltetrahydrofolate Cyclohydrolase; D008025:Ligases; D005574:Formate-Tetrahydrofolate Ligase