罗非鱼谷胱甘肽过氧化物酶1的克隆与分析

采用cDNA末端快速扩增（rapid amplification of cDNA ends，RACE）技术，克隆了罗非鱼（Oreochromis niloticus）谷胱甘肽过氧化物酶1（glutathione peroxidase1，GPx1）基因完整的编码序列（complete coding sequence，CDS）。GPx1基因全长984 bp，5UTR 56 bp，CDS 576 bp，3UTR 352 bp，PolyA 20 bp；第791~885位碱基（位于3UTR）形成1个硒半胱氨酸插入序列（selenocysteine insertion sequence，SECIS），协助174~176位密码子TGA（UGA）编码1个硒半胱氨酸（Sec）。GPx1包含191个氨基酸，分子量21.8 kDa，等电点8.04，无信号肽和潜在的N-糖基化位点。蛋白结构分析表明该基因编码蛋白为非跨膜蛋白。序列比对显示，GPx1单体具有Sec、Trp、Gln和Asn构成的催化四联体。罗非鱼GPx1与其他脊椎动物GPx1相比较，核苷酸序列相似性为43.2%~58.2%，氨基酸序列相似性为58.1%~80.6%。进化分析显示，处在分类学上不同纲的脊椎动物GPx1分别占据了不同分支。利用Swiss-Model预测了罗非鱼GPx1的3D结构，序列分析显示，GPx1可以形成1个同源四聚体。

Molecular cloning and analysis the characterization of glutathione peroxidase 1 from the nile tilapia(Oreochromis niloticus)

The complete coding sequence of glutathione peroxidase 1 (GPx1) of Nile tilapia (Oreochromis niloticus) was cloned by rapid amplification of cDNA ends (RACE). The GPx1 contains 984 bp, including a 56 bp 5-untranslated region, a 576 bp coding sequence (CDS), a 352 bp 3-untranslated region and a 20 bp PolyA tail. A selenocysteine (Sec) was encoded by the unusual stop codon, TGA, with the selenocysteine insertion sequence (SECIS) located at 3UTR. The GPx1 was predicted to encode 191 amino acids, and its molecular weight was 21.8 kDa with a pI of 8.04; neither signal peptide nor N-Glycosylation site was found. The analysis showed that GPx1 was a non-transmembrane protein, and it possessed classic catalytic tetrad comprising selenocysteine, tryptophan, glutamine and asparagine. We compared GPx1 between Nile tilapia and other vertebrate animals, and found that the similarity of nucleotide acid sequence was 43.2%~58.2%, and that of amino acid sequence was 58.1%~80.6%. Phylogenic analysis indicated that GPx1s of different classes of vertebrates split into different clusters. The 3D structure of tilapia GPx1 was predicted with Swiss-Model software, and sequence analysis suggested that GPx1 was homotetrameric.