Molecular cloning, characterization and expression analysis of peroxiredoxin 6 from disk abalone Haliotis discus discus and the antioxidant activity of its recombinant protein

Peroxiredoxins (Prxs) play an important role against various oxidative stresses and intra-cellular signal transduction. Peroxiredoxin 6 (PrxVI) was identified from the disk abalone Haliotis discus discus cDNA library and named HdPrxVI. The full length cDNA of HdPrxVI was 1457 bp with a 654 bp open reading frame (ORF) encoding 218 amino acids. The predicted molecular mass and estimated isoelectric point (pI) of HdPrxVI were 24 kDa and 7.3, respectively. The deduced amino acid sequence demonstrated the greatest degree (72.4%) of identity with Crassostrea gigas PrxVI. The conserved peroxidase catalytic center (42PVCTTE47) with a conserved cysteine residue (Cys44) and a catalytic center for PLA2 activity (27GGSWA31) were observed in the sequence, indicating that it is a member of 1-Cys Prx. Real time PCR results revealed that HdPrxVI mRNA is constitutively expressed in all tissues in a tissue-specific manner. During exposure to haemorrhagic septicaemia virus (VHSV), HdPrxVI mRNA transcription was down-regulated in the gill, suggesting that the abalone responded to the viral infection quickly, and HdPrxVI played a physiological role against virus-induced oxidative stress. The purified recombinant HdPrxVI, together with dithiothreitol (DTT), was shown to scavenge H2O2 in human leukemia THP-1 cells and provided protection against H2O2-induced apoptosis.