A Mu-class glutathione S-transferase (GSTM) from the rock shell Thais clavigera Jae-Sung Rhee a , Sheikh Raisuddin b , Dae-Sik Hwang a , Toshihiro Horiguchi c , Hyeon-Seo Cho d , Jae-Seong Lee b, ⁎ a Department of Molecular and Environmental Bioscience, Graduate School, Hanyang University, Seoul 133-791, South Korea b National Research Lab of Marine Molecular and Environmental Bioscience, Department of Chemistry, College of Natural Sciences, Hanyang University, Seoul 133-791, South Korea c Research Center for Environmental Risk, National Institute for Environmental Studies, Tsukuba, Ibaraki 305-8506, Japan d Department of Environmental Oceanography, College of Fisheries and Ocean Science, Chonnam National University, Yeosu 550-749, South Korea ABSTRACT ARTICLE INFO Article history: Received 27 March 2008 Received in revised form 19 May 2008 Accepted 20 May 2008 Available online 27 May 2008 Keywords: Thais clavigera Glutathione S-transferase-Mu Antioxidant Endocrine disrupting chemicals Imposex 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. © 2008 Elsevier Inc. All rights reserved. 1. Introduction The rock shell (Thais clavigera; Gastropoda: Muricidae) has been recognized as a potential model species for study of effects of endocrine disrupting chemicals (EDCs) (Horiguchi et al., 1994; Blackmore, 2000a; Horiguchi, 2006). The occurrence of imposex in natural populations of T. clavigera from various locations has been linked to marine EDC contamination, especially by tributyltin (TBT) (Horiguchi et al., 1997; Blackmore, 2000a; Shim et al., 2000). T. clavigera is also considered as an indicator species for heavy metal contamination in marine environ- ments (Han et al., 1997). Rockshells are carnivorous organisms, preying on other mollusks by a specialized feeding mechanism (Lau and Leung, 2004). This feeding mechanism indirectly would expose T. clavigera to toxic contaminants, which might have been accumulated by its prey (Blackmore, 2000b, Blackmore and Morton, 2002). Little is known about detoxification mechanisms including genes encoding for detoxification enzymes in T. clavigera. A few reports are available for detoxification and antioxidant defense enzymes and genes in marine mollusks, especially bivalves such as blue mussel (Mytilus edulis), Mediterranean mussel (M. galloprovincialis), brown mussel (Perna perna), green-lipped mussel (P. virdis), zebra mussel (Dreissena polymorpha), clam (Ruditapes decussates) and Pacific oyster (Crassostrea gigas)(Bebianno et al., 2004; Yang et al., 2004; Hoarau et al., 2006; Blanchette et al., 2007). Generally, studies of detoxification and antioxidant enzymes in mollusks were also aimed at using them as biomarkers of exposure to toxic chemicals in biomonitoring (Bebianno et al., 2004; Hoarau et al., 2006; Viarengo et al., 2007). Viarengo et al. (2007) listed over a dozen cytochemical biomarkers in mussels for the purpose of biomonitoring. These biomarkers also included stress responses of mollusks exposed to contaminants. Glutathione S-transferases (GSTs) play an important role in the detoxification of exogenous and endogenous metabolites and are part of antioxidant defense in all organisms (Sharma et al., 2004; Hayes et al., 2005; Masella et al., 2005). Besides the conserved detoxification and antioxidant roles, GSTs also participate in some physiological processes such as aging, aestivation, adaptation and transportation in some species (Oakley, 2005; Hayes et al., 2005; Frova, 2006). The GST family is diverse as over two dozen isoforms and subisoforms have been identified in cytosolic, microsomal, and nuclear fractions from different species (Frova, 2006; Blanchette et al., 2007). They show broad substrate specificity. GST sequences, expression, and their biochemical activities have been studied in a number of aquatic organisms including mollusks (Frova, 2006; Blanchette et al., 2007). GST-mu (GSTM) with a characteristic mu (μ) loop has been described from some marine invertebrates such as shrimp ( Litopenaeus Comparative Biochemistry and Physiology, Part C 148 (2008) 195–203 ⁎ Corresponding author. Tel.: +82 2 2220 0769; fax: +82 2 2299 9450. E-mail address: jslee2@hanyang.ac.kr (J.-S. Lee). 1532-0456/$ – see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.cbpc.2008.05.011 Contents lists available at ScienceDirect Comparative Biochemistry and Physiology, Part C journal homepage: www.elsevier.com/locate/cbpc