鱼类谷胱甘肽转移酶基因cDNA克隆及其序列分析

采用RT-PCR方法, 从鲢、鲤、鲫3种鱼类肝脏总RNA中克隆出了谷胱甘肽转移酶Pi型(GST Pi)cDNA序列, 推导了其编码的氨基酸序列。3种鱼类GST Pi的ORF全长627 bp, 编码208个氨基酸。翻译起始密码均为ATG, 终止密码子均为TGA。鱼类与哺乳动物、两栖类爪蟾以及节肢动物丝虫之间GST Pi氨基酸序列相似度平均值分别为50%、33%、15%左右。5种鱼类之间的氨基酸序列相似度较大, 其中鲤科鱼类之间平均为85%左右。我们以GST Pi为分子标记, 用最大简约数法(MP)构建了13个物种的系统进化树, 识别出两个大的单系类群: 哺乳类组成类群一(bootstrap 100); 鱼类组成类群二(bootstrap 93)。通过比较鱼类与哺乳类GST Pi N末端和C末端功能域的氨基酸组成差异,探讨了淡水鱼类GSTs承担较强的微囊藻毒素去毒能力的可能分子机制。

Cloning and the sequence analysis of the fish glutathione transferase Pi gene

Using RT-PCR method,the glutathione transferase Pi cDNAs were cloned from Cyprinus carpio,Hy-pophthalmichthys molitrix,and Carassius auratus.The open reading frames(ORFs) from the 3 fishes were 627 bp long(encoding for 208 amino acids) with the initial code ATG and the terminal code TGA.The sequence similarity was 50% between fish and mammals,33% between fish and amphibian,and 15% between fish and arthropoda,respectively.The sequence similarity was big among fishes,and the average value of the 4 cyprinids was about 85%.Phylogenetic tree was constructed for 13 species based on GST Pi amino acid sequences using MP(Maximum Parsimony) method.Two major clusters were recognized:cluster one consisted of Mammals(bootstrap 100) and cluster two consisted of fishes(bootstrap 93) .Based on the sequences analyses of N/C domain of GST Pi,we proposed the detoxification mechanism of freshwater fishes that were thought to have stronger tolerance to microcystins.