A new translational elongation factor for selenocysteyl-tRNA in eucaryotes.
In eucaryotes, selenocysteine (SeCys) was found in some selenoproteins, but SeCys-tRNA was not recognized by EF-1 alpha. A different translational elongation factor for SeCys-tRNA must therefore supply SeCys-tRNA to the machinery of selenoprotein translation. I found this factor in bovine liver extracts with a UGA-programmed ribosome binding assay. The activity of binding of [75Se]SeCys-tRNA to the UGA-programmed ribosomes was eluted in fractions 57-65 using a CM-Sephadex C-25 column, and separated from EF-1 alpha (the activity of binding of [14C]Phe-tRNA to the UUU-programmed ribosomes) in fractions 25-37. EF-1 alpha in fraction 25 could discriminate (UUU)10 for [14C]Phe-tRNA. A factor in fraction 57 could discriminate (UGA)10 for [75Se]SeCys-tRNA. The elution pattern of activity of binding of [75Se]SeCys-tRNA to the UGA-programmed ribosomes was almost identical to that of activity of protecting [75Se]SeCys-tRNA against alkaline hydrolysis (SePF activity) [FEBS Lett. 347 (1994) 137-142]. These two activities might depend on the same factor. The activity of binding of [75Se]SeCys-tRNA to the UGA-programmed ribosomes directly indicates that a factor in fraction 57 is a new translational elongation factor for SeCys-tRNA in eucaryotes.
Faculty of Pharmaceutical Sciences, Nagoya City University, Japan.
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Yamada
D000818:Animals; D002417:Cattle; D003062:Codon; D005815:Genetic Code; D008099:Liver / Q000737:chemistry; D010441:Peptide Chain Elongation, Translational; D010445:Peptide Elongation Factors / Q000302:isolation & purification / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism
D003062:Codon; D010445:Peptide Elongation Factors; D012333:RNA, Messenger; D012346:RNA, Transfer, Amino Acyl; C112705:selenocysteinyl-tRNA