Crystal Structure Analyses of Selenoprotein Biosynthesis

在古生代甲烷球菌jannaschii和嗜酸真细菌中，需要确定参与硒半胱氨酸生物合成及其共翻译掺入硒蛋白的蛋白质和RNA组分的晶体结构。相关因子有硒半胱氨酸合成酶(SELA)、延伸因子SELB、tRNASec(SELC)、丝氨酸tRNA合成酶(SerRS)和硒磷酸合成酶(SELD)。本项目的目的是探索SELA合成硒半胱氨酸的机制，阐明硒半胱氨酸特异性tRNASec的结构特点，了解其与丝氨酰-tRNA合成酶、硒半胱氨酸合成酶和延伸因子SELb的区别，从结构上阐明SELb与信使SECIS元件的相互作用，并解释硒供体硒磷酸通过硒磷酸合成酶合成的机制。这些结构将有助于理解遗传密码的这种独特扩展的机制，并有助于描述高等生物体中相应的系统。

Crystal structures of protein and RNA components involved in the biosynthesis of selenocysteine and its cotranslational incorporation into selenoproteins in the Archaeon Methanococcus jannaschii and the Bacterium Eubacterium acidaminophilum shall be determined. The pertaining factors are selenocysteine synthase (SelA), elongation factor SelB, tRNASec (SelC), seryltRNA synthetase (SerRS), and selenophosphate synthetase (SelD). Aims of the projects are to explore the mechanistics of selenocysteine synthesis by SelA, to elucidate the structural peculiarities of the selenocysteine specific tRNASec, to understand its discrimination by seryl-tRNA synthetase, by selenocysteine synthase, and by elongation factor SelB, to structurally clarify the interactions of SelB with mRNA SECIS-elements, and to explain the mechanism of synthesis of the activated selenium donor, selenophosphate, by selenophosphate synthetase. The structures shall aid in understanding the mechanisms of this unique expansion of the genetic code and in characterizing the corresponding systems in higher organisms.