硒蛋白的分子生物学研究进展

Progress in Molecular Biology Research of Selenoproteins

已有 35种硒蛋白被分离和表征 ,但许多硒蛋白及其功能仍未完全阐明 .硒半胱氨酸 (Sec)作为参入蛋白质的第 2 1种氨基酸 ,由硒蛋白mRNA上的UGA编码 .在原核生物 ,Sec参入硒蛋白的复杂机制已经较为明确 ,需要四种基因产物 (SELA、SELB、SELC和SELD)和一个存在于硒蛋白mRNA上的被称为Sec插入序列(SECIS)的茎环 (stemloop)样二级结构 .在真核生物 ,硒蛋白生物合成途径可能在SECIS的结构和位置、特异的延伸因子及其他RNA RNA或RNA 蛋白质因子之间的相互作用等方面与原核生物不同 .另外 ,哺乳动物硒蛋白mRNA上的UGA翻译为Sec的过程低效 ,特定位点的UGA密码子不同功能 (终止密码和Sec密码 )

About 35 selenoproteins. have been identified and characterized, though many have roles that have not yet been fully elucidated. Selenocysteine represents the 21(st) amino acid which is encoded by the UGA triplet in selenoproteins mRNA. Incorporation of selenocysteine in selenoproteins is rather complex but has been widely elucidated in prokaryotes. Four gene products (SELA, SELB, SELC, and SELD) and a specific stem-loop secondary structure which is termed selenocysteine insertion sequence (SECIS element) are required. However, the biosynthetic pathway of selenoproteins in eukaryotes may proceed by different routes in such aspects as the position and structure of SECIS element, specific elongation factors and other RNA-RNA or RNA-binding protein factors interactions. Observations also showed that translation of UGA as Sec in mammalian cells was an inefficient process and the regulation of the same UGA codon existing in an identical position in mRNA serves different functions (stop codon and Sec codon) might be involve in this process.