title: A novel molluscan sigma-like glutathione S-transferase from Manila clam, Ruditapes philippinarum: cloning, characterization and transcriptional profiling.
abstract: Glutathione S-transferases (GSTs) are versatile enzymes, act as primary intracellular detoxifiers and contribute to a broad range of physiological processes including cellular defense. In this study, a full-length cDNA representing a novel sigma-like GST was identified from Manila clam, Ruditapes philippinarum (RpGSTσ). RpGSTσ (884 bp) was found to possess an open reading frame of 609 bp. The encoded polypeptide (203 amino acids) had a predicted molecular mass of 23.21 kDa and an isoelectric point of 7.64. Sequence analysis revealed two conserved GST domain profiles in N- and C-termini. Alignment studies revealed that the identity between deduced peptides of RpGSTσ and known GSTσ members was relatively low (<35%), except a previously identified Manila clam GSTσ isoform (87.2%). Phylogenetic analysis indicated that RpGSTσ clustered together with molluscan GSTσ homologs, which were closely related to insect GSTσs. The RpGSTσ was subsequently cloned and expressed as recombinant protein, in order to characterize its biological activity. The recombinant RpGSTσ exhibited characteristic glutathione conjugating catalytic activity toward 1-chloro-2,4-dinitrobenzene, 3,4-dichloronitrobenzene and ethacrynic acid. It had an optimal pH and temperature of 8.0 and 35 °C, respectively. Expression profiles under normal conditions and in response to lipopolysaccharide-, poly I:C- and Vibrio tapetis-challenges were also investigated. RpGSTσ demonstrated a differential tissue distribution with robust transcription in gills of normal animals. We explored potential association of GSTσ in cellular defense during bacterial infection and found that in challenged clams, RpGSTσ gene was significantly induced in internal and external tissues, in conjunction with manganese- as well as copper-zinc superoxide dismutase (MnSOD and CuZnSOD) genes. Moreover, the induction was remarkably higher in hemocytes than in gill. Collectively, our findings suggested that RpGSTσ could play a significant role in cellular defense against oxidative stress caused by bacteria, in conjunction with other antioxidant enzymes, such as SODs.
authors.affiliation: Department of Marine Life Sciences, School of Marine Biomedical Sciences, Jeju National University, Jeju Special Self-Governing Province, 690-756, Republic of Korea.
authors.forename: Navaneethaiyer
authors.initials: N
authors.lastname: Umasuthan
authors.forename: Kasthuri Saranya
authors.initials: KS
authors.lastname: Revathy
authors.forename: Youngdeuk
authors.initials: Y
authors.lastname: Lee
authors.forename: Ilson
authors.initials: I
authors.lastname: Whang
authors.forename: Cheol Young
authors.initials: CY
authors.lastname: Choi
authors.forename: Jehee
authors.initials: J
authors.lastname: Lee
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D049872:Bivalvia / Q000201:enzymology / Q000235:genetics; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000378:metabolism; D020869:Gene Expression Profiling; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D016678:Genome; D005982:Glutathione Transferase / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D008070:Lipopolysaccharides / Q000378:metabolism / Q000494:pharmacology; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D011994:Recombinant Proteins; D013482:Superoxide Dismutase / Q000235:genetics
chemical_list: D008070:Lipopolysaccharides; D012333:RNA, Messenger; D011994:Recombinant Proteins; D013482:Superoxide Dismutase; D005982:Glutathione Transferase