Expression and Purification of A Bioactive Recombinant Fungal Immunomodulatory Protein (FIP-Lrh) from Tiger Milk Mushroom in Escherichia coli

Abstract

Fungi, particularly medicinal mushrooms, have been extensively harvested for their natural compounds for alternative medicine because they provide benefits with little to no adverse effects. FIPs, or fungal immunomodulatory proteins, are one that have been extensively studied for their immunomodulatory activities to promote lymphocyte production and subsequently enhance cytokine production. FIP-Lrh from Tiger Milk Mushroom is a novel FIP member that is believed to have pharmaceutical values, such as anti-inflammatory, anti-allergy, anti-cancer, etc. Pusparajah et al. was the first to isolate and characterise the FIP-Lrh gene from TMM. However, functional studies have been hampered due to the high cost and time required for direct purification of the mushroom protein. The present study reported the production of recombinant FIP-Lrh in the E. coli strain BL21 expression system and subsequently purified the overexpressed 6xHis-Tagged FIP-Lrh through the NiNTA purification system. The induction of expression culture with 1mM of IPTG resulted in an overexpressed 14.9kDa soluble recombinant FIP-Lrh which was subsequently purified using the NiNTA purification system. The recombinant FIP-Lrh was successfully purified, with some faint nonspecific binding of non-target protein to the NiNTA resin, which necessitated secondary purification. Recombinant FIP-Lrh produced in the E. coli expression system was quantified and yielded a concentration of 13.07 mg/mL of 500µL purified protein (total yield of 6.54mg). Further optimisation for the production of recombinant protein has to be done to obtain an adequate amount of recombinant FIP-Lrh for downstream analysis. In conclusion, the present study successfully expressed and purified the recombinant protein in the E. coli expression system.