Heterologous expression of uncharacterized parasitic nematode-specific growth factor-like protein of Setaria digitata in Pichia pastoris expression systems.

Setaria digitata is an animal filarial parasite infecting cattle and other ungulates causing mild to severe diseases, and infection of human by this nematode has also been reported. Therefore, this study was undertaken as an initial step towards the characterization of an uncharacterized gene of S. digitata, that encode for parasitic nematode-specific growth factor-like protein to which Wucheraria bancrofti and other filarial and parasitic nematodes have homologous counterparts (revealed by bioinformatic analyses), by means of protein expression and purification in Pichia pastoris. In Pichia expression system, S. digitata uncharacterized protein (SDUP) was expressed both as secretory and intracellular protein. SDS-PAGE and western blot analyses revealed expression of recombinant SDUP in P. pastoris, showing a band of 23.8 kDa, which is similar to theoretical molecular weight and also this protein was shown to be more concentrated into insoluble fraction than soluble fraction of cell lysates suggesting that the protein to be more hydrophobic than hydrophilic. Recombinant SDUP was successfully purified using Ni-NTA affinity chromatography purification technique and three dimensional structural studies of the purified protein are currently being progressed. This is the first report of the expression of S. digitata protein in P. pastoris.