Open AccessStructure of a tRNA-dependent kinase essential for selenocysteine decoding
Author(s) -
Yuhei Araiso,
R. Lynn Sherrer,
Ryuichiro Ishitani,
Joanne M. L. Ho,
Dieter Söll,
Osamu Nureki
Publication year - 2009
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.0908861106
Subject(s) - adenylate kinase , selenocysteine , transfer rna , biochemistry , biology , enzyme , amino acid , stereochemistry , kinase , rna , chemistry , gene , cysteine
Compared to bacteria, archaea and eukaryotes employ an additional enzyme for the biosynthesis of selenocysteine (Sec), the 21st natural amino acid (aa). An essential RNA-dependent kinase,O -phosphoseryl-tRNASec kinase (PSTK), converts seryl-tRNASec toO -phosphoseryl-tRNASec , the immediate precursor of selenocysteinyl-tRNASec . The sequence ofMethanocaldococcus jannaschii PSTK (MjPSTK) suggests an N-terminal kinase domain (177 aa) followed by a presumed tRNA binding region (75 aa). The structures of MjPSTK complexed with ADP and AMPPNP revealed that this enzyme belongs to the P-loop kinase class, and that the kinase domain is closely related to gluconate kinase and adenylate kinase. ATP is bound by the P-loop domain (residues 11–18). Formed by antiparallel dimerization of two PSTK monomers, the enzyme structure shows a deep groove with positive electrostatic potential. Located in this groove is the enzyme's active site, which biochemical and genetic data suggest is composed of Asp-41, Arg-44, Glu-55, Tyr-82, Tyr-83, Met-86, and Met-132. Based on structural comparison withEscherichia coli adenylate kinase a docking model was generated that assigns these amino acids to the recognition of the terminal A76-Ser moieties of Ser-tRNASec . The geometry and electrostatic environment of the groove in MjPSTK are perfectly complementary to the unusually long acceptor helix of tRNASec .