Rhee Jae-Sung, Raisuddin Sheikh, Hwang Dae-Sik, Horiguchi Toshihiro, Cho Hyeon-Seo, Lee Jae-Seong
Department of Molecular and Environmental Bioscience, Graduate School, Hanyang University, Seoul 133-791, South Korea.
Comp Biochem Physiol C Toxicol Pharmacol. 2008 Sep;148(3):195-203. doi: 10.1016/j.cbpc.2008.05.011. Epub 2008 May 27.
The rock shell (Thais clavigera) has attracted interest due to high frequency of imposex induced by endocrine disrupting chemicals (EDCs) in its natural populations. Oxidative stress is one of the mechanisms of action of EDCs. Glutathione S-transferases (GSTs) play an important role in antioxidant defense protecting the cells from oxidative stress. So far, there is no information on antioxidant defense or detoxification genes from T. clavigera. We cloned the full length cDNA sequence for a Mu-class of GST gene from T. clavigera (Tc-GSTM) and purified recombinant Tc-GSTM protein by bacterial expression. The deduced amino acid sequence of Tc-GSTM exhibited 45 to 66% identity with other Mu-class GSTs. Real-time RT-PCR analysis showed highest expression of Tc-GSTM in gill, while reproductive organs showed low expression. The biochemical characteristics of purified recombinant Tc-GSTM were typical, and thus Tc-GSTM showed highest specific activity for the universal GST substrate, 1-chloro-2,4-dinitrobenzene (CDNB). After exposure to prooxidant H(2)O(2), transformed Escherichia coli containing Tc-GSTM showed higher survival rate compared to control bacteria without expressed Tc-GSTM. The present study reveals a conserved antioxidant role for GSTM in rock shells, and the tissue-specific differences in Tc-GSTM transcripts would partly reflect vulnerability of reproductive organs to chemically induced oxidative stress.
荔枝螺（Thais clavigera）因其自然种群中内分泌干扰化学物质（EDCs）诱导的性畸变频率较高而受到关注。氧化应激是EDCs的作用机制之一。谷胱甘肽S-转移酶（GSTs）在抗氧化防御中发挥重要作用，保护细胞免受氧化应激。到目前为止，尚无关于荔枝螺抗氧化防御或解毒基因的信息。我们克隆了荔枝螺Mu类GST基因（Tc-GSTM）的全长cDNA序列，并通过细菌表达纯化了重组Tc-GSTM蛋白。Tc-GSTM推导的氨基酸序列与其他Mu类GSTs的同一性为45%至66%。实时RT-PCR分析显示，Tc-GSTM在鳃中的表达最高，而在生殖器官中的表达较低。纯化的重组Tc-GSTM的生化特性典型，因此Tc-GSTM对通用GST底物1-氯-2,4-二硝基苯（CDNB）表现出最高的比活性。暴露于促氧化剂H₂O₂后，含有Tc-GSTM的转化大肠杆菌比未表达Tc-GSTM的对照细菌显示出更高的存活率。本研究揭示了GSTM在荔枝螺中具有保守的抗氧化作用，并且Tc-GSTM转录本的组织特异性差异将部分反映生殖器官对化学诱导氧化应激的易感性。
