Identification and characterization of phosphoseryl-tRNA[Ser]Sec kinase.
In 1970, a kinase activity that phosphorylated a minor species of seryl-tRNA to form phosphoseryl-tRNA was found in rooster liver [Maenpaa, P. H. & Bernfield, M. R. (1970) Proc. Natl. Acad. Sci. USA 67, 688-695], and a minor seryl-tRNA that decoded the nonsense UGA was detected in bovine liver. The phosphoseryl-tRNA and the minor UGA-decoding seryl-tRNA were subsequently identified as selenocysteine (Sec) tRNA[Ser]Sec, but the kinase activity remained elusive. Herein, by using a comparative genomics approach that searched completely sequenced archaeal genomes for a kinase-like protein with a pattern of occurrence similar to that of components of Sec insertion machinery, we detected a candidate gene for mammalian phosphoseryl-tRNA[Ser]Sec kinase (pstk). Mouse pstk was cloned, and the gene product (PSTK) was expressed and characterized. PSTK specifically phosphorylated the seryl moiety on seryl-tRNA[Ser]Sec and, in addition, had a requirement for ATP and Mg2+. Proteins with homology to mammalian PSTK occur in Drosophila, Caenorhabditis elegans, Methanopyrus kandleri, and Methanococcus jannaschii, suggesting a conservation of its function across archaea and eukaryotes that synthesize selenoproteins and the absence of this function in bacteria, plants, and yeast. The fact that PSTK has been highly conserved in evolution suggests that it plays an important role in selenoprotein biosynthesis and/or regulation.
Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Bradley A
BA
Carlson
Xue-Ming
XM
Xu
Gregory V
GV
Kryukov
Mahadev
M
Rao
Marla J
MJ
Berry
Vadim N
VN
Gladyshev
Dolph L
DL
Hatfield
D000595:Amino Acid Sequence; D001483:Base Sequence; D019295:Computational Biology; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010770:Phosphotransferases / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*; D012362:RNA, Transfer, Ser / Q000378:metabolism*
D012346:RNA, Transfer, Amino Acyl; D012362:RNA, Transfer, Ser; C112705:selenocysteinyl-tRNA; D010770:Phosphotransferases