Carlson Bradley A, Xu Xue-Ming, Kryukov Gregory V, Rao Mahadev, Berry Marla J, Gladyshev Vadim N, Hatfield Dolph L
Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Proc Natl Acad Sci U S A. 2004 Aug 31;101(35):12848-53. doi: 10.1073/pnas.0402636101. Epub 2004 Aug 18.
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.
1970年，在公鸡肝脏中发现了一种激酶活性，该活性可使一种次要的丝氨酰 - tRNA磷酸化形成磷酸丝氨酰 - tRNA[Maenpaa, P. H. & Bernfield, M. R. (1970) Proc. Natl. Acad. Sci. USA 67, 688 - 695]，并且在牛肝脏中检测到了一种可解码无义密码子UGA的次要丝氨酰 - tRNA。随后，磷酸丝氨酰 - tRNA和次要的UGA解码丝氨酰 - tRNA被鉴定为硒代半胱氨酸（Sec）tRNA[Ser]Sec，但该激酶活性仍不明确。在此，通过使用一种比较基因组学方法，在完全测序的古细菌基因组中搜索一种激酶样蛋白，其出现模式与Sec插入机制的组分相似，我们检测到了哺乳动物磷酸丝氨酰 - tRNA[Ser]Sec激酶（pstk）的一个候选基因。克隆了小鼠pstk，并对基因产物（PSTK）进行了表达和特性分析。PSTK特异性地使丝氨酰 - tRNA[Ser]Sec上的丝氨酰部分磷酸化，此外，还需要ATP和Mg2 +。与哺乳动物PSTK具有同源性的蛋白质存在于果蝇、秀丽隐杆线虫、坎氏甲烷嗜热菌和詹氏甲烷球菌中，这表明在合成硒蛋白的古细菌和真核生物中其功能具有保守性，而在细菌、植物和酵母中则不存在该功能。PSTK在进化过程中高度保守这一事实表明它在硒蛋白生物合成和/或调节中起重要作用。
