A factor protecting mammalian [75Se]SeCys-tRNA is different from EF-1 alpha.
In Escherichia coli, an elongation factor (EF-Tu-like) specific to SeCys-tRNA, SELB, has been identified; however, a mammalian counterpart of SELB has not been reported to date. We searched for and found this factor in bovine liver extracts using the assay of [75Se]SeCys-tRNA protecting activity against alkaline hydrolysis (SePF activity). We found SePF activity in the protein extracts of the precipitate (microsomal fraction) collected at 150,000 x g from bovine liver. The proteins were separated by Sephacryl S-300 chromatography, and the SePF and EF-1 alpha activities were found in the same fraction, indicating that SePF and EF-1 alpha have the same molecular mass (approximately 50 kDa). We then chromatographed this active fraction using CM-Sephadex C-25 columns. The SePF activity was eluted after the peak of EF-1 alpha activity. This result indicated that this SePF activity was not dependent on EF-1 alpha. In addition to performing these two chromatographies, we investigated pure EF-1 alpha from Bombyx mori but could not detect any SePF activity in B. mori EF-1 alpha. Thus we showed that the SePF activity in bovine liver differs from that of EF-1 alpha in eukaryotes. Therefore the factor protecting [75Se]SeCys-tRNA in bovine liver is not EF-1 alpha and must be a SELB-like factor.
Faculty of Pharmaceutical Sciences, Nagoya City University, Japan.
K
K
Yamada
T
T
Mizutani
S
S
Ejiri
T
T
Totsuka
D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry / Q000494:pharmacology*; D012831:Bombyx / Q000737:chemistry; D002417:Cattle; D002845:Chromatography; D004926:Escherichia coli / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008099:Liver / Q000737:chemistry*; D008970:Molecular Weight; D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors / Q000737:chemistry / Q000494:pharmacology*; D012345:RNA, Transfer, Amino Acid-Specific / Q000378:metabolism*
D001426:Bacterial Proteins; D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors; D012345:RNA, Transfer, Amino Acid-Specific; C061878:SelB protein, Bacteria; C036928:tRNA, selenocysteine-