Characterization and evolutionary history of an archaeal kinase involved in selenocysteinyl-tRNA formation
- Yale Univ., New Haven, CT (United States). Dept. of Molecular Biophysics. Dept. of Biochemistry; DOE/OSTI
- Yale Univ., New Haven, CT (United States). Dept. of Molecular Biophysics. Dept. of Biochemistry
- Yale Univ., New Haven, CT (United States). Dept. of Molecular Biophysics. Dept. of Biochemistry. Dept. of Chemistry
Selenocysteine (Sec)-decoding archaea and eukaryotes employ a unique route of Sec-tRNASec synthesis in which O-phosphoseryl-tRNASec kinase (PSTK) phosphorylates Ser-tRNASec to produce the O-phosphoseryl-tRNASec (Sep-tRNASec) substrate that Sep-tRNA:Sec-tRNA synthase (SepSecS) converts to Sec-tRNASec. This study presents a biochemical characterization of Methanocaldococcus jannaschii PSTK, including kinetics of Sep-tRNASec formation (Km for Ser-tRNASec of 40 nM and ATP of 2.6 mM). PSTK binds both Ser-tRNASec and tRNASec with high affinity (Kd values of 53 nM and 39 nM, respectively). The ATPase activity of PSTK may be activated via an induced fit mechanism in which binding of tRNASec specifically stimulates hydrolysis. Albeit with lower activity than ATP, PSTK utilizes GTP, CTP, UTP and dATP as phosphatedonors. Homology with related kinases allowed prediction of the ATPase active site, comprised of phosphate-binding loop (P-loop), Walker B and RxxxR motifs. Gly14, Lys17, Ser18, Asp41, Arg116 and Arg120 mutations resulted in enzymes with decreased activity highlighting the importance of these conserved motifs in PSTK catalysis both in vivo and in vitro. Phylogenetic analysis of PSTK in the context of its ‘DxTN’ kinase family shows that PSTK co-evolved precisely with SepSecS and indicates the presence of a previously unidentified PSTK in Plasmodium species.
- Research Organization:
- Yale Univ., New Haven, CT (United States)
- Sponsoring Organization:
- National Institutes of Health (NIH); USDOE Office of Science (SC), Biological and Environmental Research (BER). Biological Systems Science Division
- OSTI ID:
- 1625422
- 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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