Pre-folding purification procedures for inclusion body-derived non-tagged cationic recombinant proteins with multiple disulfide bonds for efficient refolding.

The production of disulfide-containing recombinant proteins often requires refolding of inclusion bodies before purification. A pre-refolding purification step is crucial for effective refolding because impurities in the inclusion bodies interfere with refolding and subsequent purification. This study presents a new pre-refolding procedure using a reversible S-cationization technique for protein solubilization and purification by reversed-phase high performance liquid chromatography. This pre-folding purification step improves refolding yield by effectively removing the refolding inhibitors from contaminates from bacterial inclusion bodies, and reducing proteolytically degraded products. Because this procedure does not require a peptide tag for affinity purification, it is a superior technique to subsequently perform a simplified downstream process wherein the affinity tag needs to be removed. This study reports improved refolding and purification procedure to obtain the highly cationic (pI = 9.25) mouse vascular endothelial cell growth factor (188 amino acids form) that is used as a model protein in our study; this protein shows a homodimeric conformation and possesses multiple disulfides.