Characterization of Human Selenocysteine Synthase Involved in Selenoprotein Biosynthesis

概要

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Bacterial selenocysteine synthase is a pyridoxal 5'-phosphate-dependent enzyme that catalyzes the conversion of seryl-tRNASec to selenocysteyl-tRNASec for selenoprotein biosynthesis. Human selenocysteine synthase(SecS),originally annotated as SLA/LP, was previously reported to operate in selenocysteyl-tRNASec synthesis, but the mechanism of conversion from Ser-tRNASec by the eukaryotic enzyme remained unresolved. Herein, the human cDNA encoding SecS has been cloned and overexpressed in Escherichia coli. SecS was co-purified with E. coli tRNAs, which was revealed to contain tRNASec by PCR analysis. The purified enzyme exhibited a UV-visible absorption maximum at 420 nm characteristic of pyridoxal 5'-phosphate-dependent enzymes. In vitro selenocysteyl-tRNASec synthesis assay suggests that the formation of phosphoseryl-tRNASec is essential for human seryl-tRNASec, but not archaeal seryl-tRNASec to be converted to selenocysteyl-tRNASec by human SecS.
日本微量元素学会の論文