Structural insights into RNA-dependent eukaryal and archaeal selenocysteine formation
- Tokyo Institute of Technology (Japan). Graduate SChool of Bioscience and Biotechnology. Dept. of Biological Information; DOE/OSTI
- Yale Univ., New Haven, CT (United States). Dept. of Molecular Biophysics and Biochemistry
- Tokyo Institute of Technology (Japan). Graduate SChool of Bioscience and Biotechnology. Dept. of Biological Information
- RIKEN, Saitama (Japan). Biomolecular Characterization
- Tokyo Institute of Technology (Japan). Graduate SChool of Bioscience and Biotechnology. Dept. of Biological Information; SORST, Saitama (Japan). JST
The micronutrient selenium is present in proteins as selenocysteine (Sec). In eukaryotes and archaea, Sec is formed in a tRNA-dependent conversion of O-phosphoserine (Sep) by O-phosphoseryltRNA:selenocysteinyl-tRNA synthase (SepSecS). Here, we present the crystal structure of Methanococcus maripaludis SepSecS complexed with PLP at 2.5 Å resolution. SepSecS, a member of the Fold Type I PLP enzyme family, forms an (a2)2 homotetramer through its N-terminal extension. The active site lies on the dimer interface with each monomer contributing essential residues. In contrast to other Fold Type I PLP enzymes, Asn247 in SepSecS replaces the conserved Asp in binding the pyridinium nitrogen of PLP. A structural comparison with Escherichia coli selenocysteine lyase allowed construction of a model of Sep binding to the SepSecS catalytic site. Mutations of three conserved active site arginines (Arg72, Arg94, Arg307), protruding from the neighboring subunit, led to loss of in vivo and in vitro activity. The lack of active site cysteines demonstrates that a perselenide is not involved in SepSecS-catalyzed Sec formation; instead, the conserved arginines may facilitate the selenation reaction. Structural phylogeny shows that SepSecS evolved early in the history of PLP enzymes, and indicates that tRNA-dependent Sec formation is a primordial process.
- Research Organization:
- Yale Univ., New Haven, CT (United States)
- Sponsoring Organization:
- Japan Society for the Promotion of Science (JSPS); National Institutes of Health (NIH); National Science Foundation (NSF); USDOE Office of Science (SC), Biological and Environmental Research (BER). Biological Systems Science Division
- OSTI ID:
- 1625420
- Journal Information:
- Nucleic Acids Research, Journal Name: Nucleic Acids Research Journal Issue: 4 Vol. 36; ISSN 0305-1048
- Publisher:
- Oxford University PressCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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