Inclusion Bodies Be Gone

Scientists routinely express heterologous proteins in Escherichia coli. However, these proteins may not fold properly in the bacteria, causing them to aggregate and form insoluble inclusion bodies. Scientists traditionally denature these inclusion bodies with either 8 M urea or 6 M guanidine hydrochloride to solubilize them. These proteins must then be renatured by replacing the denaturants with a gentler buffer. Unfortunately, this process is highly empirical and laborious, and it often results

Amy Constantine

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Researchers at Novagen employed a solubility model developed by D.L. Wilkinson and R.G. Harrison to identify E. coli proteins likely to confer the highest solubility on a fusion partner.¹ They then narrowed the range of choices based on size and published data, to end up with three candidate proteins: NusA, bacterioferritin (BFR), and GrpE. Western blot and SDS-PAGE analyses revealed that NusA fusion proteins were more soluble than were fusions with either BFR or GrpE, or with thioredoxin (TRX) and glutathione-S-transferase (GST), two proteins traditionally used to increase solubility of target proteins. A 54-kDa tyrosinase was efficiently expressed as a NusA fusion, suggesting that the Nus·Tag may be a good carrier for large, insoluble proteins.

According to Mark Lepinske, marketing communications manager at Novagen, "The primary feature of the new Novagen Nus·Tag System is the tremendous solubility this new tag tends to confer on a target protein. I don't know ...

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