New p40 Fusion Domain Method Creates Functional Proteins from Bacterial Inclusion Bodies

Recombinant protein production, particularly in bacterial systems like Escherichia coli, often faces challenges when target proteins misfold and aggregate into inclusion bodies. These dense, insoluble aggregates are typically non-functional, necessitating complex and often inefficient refolding processes to recover active protein. This study addresses the critical need for a simpler, more efficient method to produce functional proteins directly from inclusion bodies, bypassing traditional refolding steps.

The p40 fusion domain dramatically improved the functional recovery of target proteins from inclusion bodies. For p40-hGH, despite 80% of the total expressed protein forming inclusion bodies, 75% of the solubilized hGH was functionally active, a significant increase compared to less than 5% activity observed for unfused hGH from inclusion bodies. Similarly, p40-IL-2 yielded 70% functional activity directly from inclusion bodies, representing a remarkable 15-fold increase in active protein yield compared to the unfused control. > The most impactful finding was that the p40 fusion strategy achieved a 2.5-fold higher total active protein yield per liter of bacterial culture compared to optimized soluble expression methods, demonstrating superior overall productivity. Furthermore, the specific activity of the p40-fused proteins was found to be comparable to their soluble, correctly folded counterparts, with no significant difference (p>0.05) observed in receptor binding or cell proliferation assays, indicating high-quality protein production.