Yamada K, Mizutani T, Ejiri S, Totsuka T. A factor protecting mammalian [75Se]SeCys-tRNA is different from EF-1 alpha.
FEBS Lett 1994;
347:137-42. [PMID:
8033991 DOI:
10.1016/0014-5793(94)00523-0]
[Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
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.
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