Mitochondrial thioredoxin-2 from disk abalone (Haliotis discus discus):: Molecular characterization, tissue expression and DNA protection activity of its recombinant protein

Thioredoxin-2 is a mitochondria-specific member of the thioredoxin (TRx) super-family that plays an important role as a component of the mitochondrial antioxidant system. The gene coding mitochondrial TRx-2 was isolated from the disk abalone (Haliotis discus discus) cDNA library, denoted as AbTRx-2. It contains 1214-bp full length with 519-bp open reading frame, encoding 173 amino acids. AbTRx-2 showed characteristic TRx active site at (96)WCGPC(100) and mitochondrial targeting peptide at the N-terminal amino acid sequence. The deduced amino acid comparison showed that AbTRx-2 shares 43 and 42% identity with Xenopus laevis and human TRx-2, respectively. Purified recombinant AbTRx-2 fusion protein was shown to catalyze insulin reduction and protect supercoiled plasmid DNA from damages induced by metal-catalyzed generation of reactive oxygen species. Constitutive AbTRx-2 mRNA was detected in gill, mantle, gonad, abductor muscle, digestive tract, and hemocytes, in a tissue specific manner. The AbTRx-2 mRNA was up-regulated in gill and digestive tract tissues initially at 3 h post-injection of H2O2 and maintained higher level at 6 h. Our results suggest that abalone TRx-2 may play an important role in regulating oxidative stress in mitochondria by catalyzing protein disulfide reduction, scavenging of ROS, and minimizing the DNA damage. (c) 2008 Elsevier Inc. All rights reserved.