EXPRESSION OF EUKARYOTIC PROTEINS IN SOLUBLE FORM IN ESCHERICHIA-COLI

At the optimum temperature for its growth (37 degrees C), Escherichia coli tends to accumulate heterologous proteins in insoluble form. Fusi on protein technology has been used to increase the solubility of over expressed proteins in this organism, but with variable degrees of succ ess. Fusion to a mutant form of DsbA (DsbA(mut)) confers higher levels of solubility to heterologous proteins in a reproducible way, even wh en E. coli is grown at 37 degrees C. We have shown this to be true wit h a diverse sample of eukaryotic proteins: IGF-I, IGFBP-3, 3C proteina se, TGF beta-2, sTGF beta-RII, BDNF, GDNF, mEGFBP, leptin, and GFP. In addition, we have investigated the effects of charge average and prol ine content on the solubility of DsbA(mut) fusions. Coexpression of a protein prolyl isomerase [cyclophilin (L-)] and modification of select ed asparagine residues to aspartic acid appear to have beneficial effe cts on the accumulation of soluble heterologous proteins. (C) 1998 Aca demic Press.