Expression and purification of ecdysteroid-regulated protein from Chinese mitten crab Eriocheir sinensis in E. coli

The glutathione S-transferase (GST) fusion protein system is widely used for high-level expression and efficient purification of recombinant proteins from bacteria. The goal of this study was to clone, efficiently express and purify the ecdysteroid-regulated protein (ERP) in the form of a GST fusion protein. The mature peptide-coding cDNA fragment was extracted from Chinese mitten crap (Eriocheir sinensis), and then after using PCR to obtain the open reading frame, a recombinant plasmid designated pGEX-4T-1_ERP was successfully generated and showed to efficiently express the ERP fusion protein as determined by SDS-PAGE. The resulting expressed protein was successfully purified by a combination of affinity and conventional chromatographic methods. After purification, the recombinant protein showed the expected size of 41 kDa on SDS-PAGE gels which was further confirmed by mass spectrometry and western blotting. Purification of recombinant protein was achieved by fast protein liquid chromatography. About 2.4 mg/l recombinant protein with purity more than 80 % was obtained.