title: Mitochondrial thioredoxin-2 from Manila clam (Ruditapes philippinarum) is a potent antioxidant enzyme involved in antibacterial response.
abstract: Thioredoxin (TRx) is a ubiquitous protein involved in the regulation of multiple biological processes. The TRx-2 isoform is exclusively expressed in mitochondria, where it contributes to mitochondrial redox state maintenance. In the present study, a novel thioredoxin-2 gene was identified in the Manila clam, Ruditapes philippinarum. The full-length sequence of RpTRx-2 (1561 bp) consists of a 498 bp coding region encoding a 166 amino acid protein. The N-terminal region of RpTRx-2 harbors a mitochondrial localization signal (56 amino acids), while the C-terminal portion contains the characteristic (89)WCGPC(93) catalytic active site. Phylogenetic analysis revealed that RpTRx-2 is closest to its ortholog from abalone. The broad distribution pattern of RpTRx-2 mRNA in healthy animal tissues implicates a generally significant function in normal clam physiology. The transcription level of RpTRx-2, however, is highest in hemocytes. Lipopolysaccharide and Vibrio tapetis bacterium caused up-regulation of the RpTrx-2 transcript levels in gill and hemocytes. Interestingly, clam manganese superoxide dismutase (MnSOD) mRNA levels in hemocytes elicited a corresponding response to these immune challenges. RpTRx-2 was recombinantly expressed in Escherichia coli BL21 (DE3) and used in insulin disulfide reduction assay as well as metal-catalyzed oxidation assay to elucidate its antioxidant property by reducing substrate and protecting super-coiled DNA from oxidative damage through free radical scavenging, respectively. Collectively, our data indicated that RpTRx-2, a mitochondrial TRx-2 family member, is an antioxidant enzyme that may be involved in antibacterial defense of clams.
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: Jehee
authors.initials: J
authors.lastname: Lee
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000975:Antioxidants; D001483:Base Sequence; D049872:Bivalvia / Q000201:enzymology* / Q000276:immunology* / Q000382:microbiology; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000276:immunology*; D008928:Mitochondria / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D011487:Protein Conformation; D012333:RNA, Messenger / Q000378:metabolism; D013879:Thioredoxins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000276:immunology
chemical_list: D000975:Antioxidants; D012333:RNA, Messenger; D013879:Thioredoxins