Ralph Yamamoto

[26] Purification of recombinant human interferon β expressed in Escherichia coli

Publisher Summary This chapter discusses the purification of recombinant human interferon β (IFN-β) expressed in Escherichia coli . Many purification methods developed for native (glycosylated) human IFN-β are not applicable to nonglycosylated recombinant IFN-β obtained after expression in Escherichia coli . A method is developed for large-scale purification of recombinant IFN-β and IFN-β. IFN-β is a highly active and stable form of IFN-β containing a cysteine to serine substitution at position 17 introduced by in vitro site-specific mutagenesis. The interaction of sodium dodecyl sulfate (SDS) and IFN-β has been utilized in the purification scheme presented. Recombinant human interferons have been expressed in mammalian, insect, yeast, and bacterial cells. A method for the purification of recombinant human IFN-β and an active variant, IFN-β, obtained through genetic engineering, is described. Both proteins are nonglycosylated, lack the amino-terminal methionine present in the native protein and occur as aggregates when expressed at high levels of E. coli . Aggregation is presumably a consequence of the intrinsic hydrophobicity of IFN-β. Detergents, such as sodium dodecyl sulfate or sarkosyl, and chaotropic agents, such as guanidine hydrochloride, effectively solubilize the biological activity present in E. coli cells. This observation and the fact that IFN-β at neutral pH is poorly soluble in the absence of ionic detergents, led to a purification scheme based on the interaction of IFN-β with dodecyl sulfate.