Refolding of recombinant porcine growth hormone in a reducing environment limits in vitro aggregate formation

Recombinant porcine growth hormone (rPGH) solubilized from bacterial inclusion bodies (IBs) using a cationic surfactant was oxidized to form disulphide bonds in a simple buffer solution containing 2-mercaptoethanol within an empirically derived optimal molar ratio of 2-mercaptoethanol:protein. A final yield of 55% monomeric rPGH was achieved at protein concentrations of up to 5 mg/ml without the need for removal of the 2-mercaptoethanol or the use of chaotrophic agents. In the absence of 2-mercaptoethanol only 15% monomeric rPGH was obtained, with the majority forming higher molecular weight aggregates. Using the procedure derived for porcine growth hormone, it may be possible to obtain high yields of native protein and overcome the need for using low protein concentrations and chaotrophic agents during in vitro refolding of other disulphide bonded recombinant proteins.