Isolation and analysis of partial cDNA sequence coding for superoxide dismutase in Wuchereria bancrofti

Expression and characterization of Cu/Zn superoxide dismutase from Wuchereria bancrofti

The Cu/Zn superoxide dismutase gene from Wuchereria bancrofti (Cu/Zn WbSOD) was isolated by PCR using degeneracy primers. The complete Cu/Zn WbSOD consisted of 1,032 nucleotides containing 4 exons (477 nucleotides) and 3 introns. The molecular phylogenetic analysis of the Cu/Zn WbSOD gene in comparison with those from other organisms revealed that the gene was classified in the same clade to those of filarial Brugia malayi and Brugia pahangi (bootstrap value at 90). The nucleotide and deduced amino acid sequences of Cu/Zn WbSOD exhibited the similarity to those of intracellular Cu/Zn SOD of B. malayi and B. pahangi. The amino acid comparison of Cu/Zn WbSOD to others revealed that the binding sites and active sites were conserved. The expression of this gene yielded 16.366 kDa in size. After Ni-IDA column purification, the enzyme showed specific activity of 8.5 U/mg and 42.1% yield. The enzyme activity was inhibited when 6 mM KCN was added.

Translationally controlled tumor protein of Brugia malayi functions as an antioxidant protein

Translationally controlled tumor protein (TCTP) is one of the most abundantly expressed proteins in the filarial parasites as well as in the other organisms. Several functions have been suggested for TCTP family of proteins ranging from calcium binding to histamine release function. However, its physiological function is still a mystery. Previous studies showed that the expression of TCTP is increased several-fold during oxidative stress. In the present work, we report the putative antioxidant function of Brugia malayi TCTP (BmTCTP). When tested in vitro, rBmTCTP could be reduced by a variety of reducing agents including thioredoxin. Such reduced form of rBmTCTP was able to protect DNA from oxidative damage, suggesting that BmTCTP may have an antioxidant function in the parasite. Sequence analysis of filarial TCTPs revealed that there are three cysteine amino acids located in the central portion of the protein. Subsequent targeted residue modification studies showed that these cysteine residues in rBmTCTP are critical for its antioxidant function. To determine the significance of this finding, rBmTCTP was overexpressed in vivo in Escherichia coli and subjected to oxidative stress. These studies showed that rBmTCTP significantly protected cells form oxidative damage. Taken together, these findings suggest that BmTCTP might be functioning as a non-classical antioxidant protein in the filarial parasites.