Use Intein Cleavable Polyhydroxyalkanoate Synthase Fusions to Improve Protein Solubility

Recombinant E. coli producing intein-cleavable polyhydroxyalkanoate synthase fusions mediates the intracellular formation of polyhydroxyalkanoate (PHA) particles densely coated with intein-cleavable target protein fusion. These PHA particles can be efficiently purified from lysed cells. The self-cleaving intein performs as a bio-linker between the PHA synthase and the target protein. The tagless target protein can be released as pure soluble protein from the PHA particles by a simple pH reduction to 6.0. Here we describe that PHA particles serve as bioseparation resin for purification of soluble target proteins with pharmaceutical grade purity, similar to commercial affinity separation technologies. This cost-effective technique does not involve multiple complicated protein purification procedures, and we have exploited this approach to purify six target proteins: green fluorescent protein (GFP) from A. victoria, antigen Rv1626 from M. tuberculosis, the immunoglobulin G (IgG) binding ZZ domain of protein A derived from Staphylococcus aureus, human tumor necrosis factor alpha (TNFα), human granulocyte colony-stimulating factor (G-CSF), and human interferon alpha 2b (IFNα2b).