Some evidence of the enzymatic conversion of bovine suppressor phosphoseryl-tRNA to selenocysteyl-tRNA.
In order to clarify the mechanisms of selenocysteine incorporation into glutathione peroxidase, some evidence to show the in vitro conversion of phosphoseryl-tRNA to selenocysteyl-tRNA is reported. [3H]Phosphoseryl-tRNA was incubated in a reaction mixture composed of SeO2, glutathione and NADPH in the presence of selenium-transferase partially purified. Analyses of amino acids on the product tRNA showed that a part (4%) of [3H]phosphoseryl-tRNA was changed to [3H]selenocysteyl-tRNA. The conversion from seryl-tRNAsu or major seryl-tRNAIGA was not found. Selenium-transferase was essential for the conversion. [3H]Selenocysteine, liberated from the tRNA, was modified with iodoacetic acid. The product was confirmed to be carboxymethyl-selenocysteine by two-dimensional TLC. Selenocysteyl-tRNAsu should be used to synthesize glutathione peroxidase by co-translational mechanisms.
Mizutani
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Faculty of Pharmaceutical Sciences, Nagoya City University, Japan.
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002417:Cattle; D002855:Chromatography, Thin Layer; D003545:Cysteine / Q000031:analogs & derivatives* / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D012343:RNA, Transfer / Q000378:metabolism*; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*; D012643:Selenium / Q000378:metabolism*; D017279:Selenocysteine; D014166:Transferases / Q000302:isolation & purification / Q000378:metabolism*
D000596:Amino Acids; D012346:RNA, Transfer, Amino Acyl; C112705:selenocysteinyl-tRNA; C043354:tRNA, O(beta)-phosphoserine-; D017279:Selenocysteine; D009249:NADP; D012343:RNA, Transfer; D014166:Transferases; C060600:selenium transferase; D005978:Glutathione; D012643:Selenium; D003545:Cysteine