A single step method for the solubilization and refolding of recombinant protein from E. coli inclusion bodies

Expression of recombinant porcine growth hormone (rpGH) in E. coli cells resulted in the accumulation of the rpGH within inclusion bodies (IBs). The IBs were solubilized and the rpGH refolded in a single step using a cationic surfactant, N-cetyl pyridinium chloride (CPC; C21H38ClN) in the absence of reducing agents. No additional dialysis or rapid dilution steps of the solubilizing agent were required to obtain a 30% yield of refolded and oxidized rpGH monomer at protein concentrations of up to 15-20 mg/mL. In contrast, the refolding in vitro of rpGH in the absence of CPC resulted in the formation of significant amounts of higher molecular weight aggregate at the expense of the biologically active monomer. The fluorescence spectrum of the purified refolded rpGH was indistinguishable from that of biologically active, pituitary derived porcine GH and reverse-phase HPLC analysis of the purified rpGH showed similar retention times to that of pituitary GH. It is likely that the use of cetylpyridinium chloride is generally applicable to the simplified high yield recovery of biologically active recombinant proteins from IBs.