Characterization of E. coli-derived recombinant human interferon-beta as compared with fibroblast human interferon-beta

Homogeneous E. coli-derived recombinant human interferon-beta (E. coli-rHuIFN-beta) was characterized in order to elucidate its physicochemical properties, as compared with those of fibroblast human interferon-beta (fibroblast HuIFN-beta). Purified E. coli-rHuIFN-beta and fibroblast HuIFN-beta exhibited a single band of Mr 19,000 and 23,000, respectively, on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The primary structure of E. coli-rHuIFN-beta was identical to the prediction from the cDNA sequence. Furthermore, both the circular dichroism (CD) spectra and the 1H nuclear magnetic resonance (NMR) spectra of E. coli-rHuIFN-beta and fibroblast HuIFN-beta at pH 6.8 were closely similar to each other. On the other hand, on reverse-phase high-performance liquid chromatography (HPLC) using a C18 column, the retention time of E. coli-rHuIFN-beta was longer than that of fibroblast HuIFN-beta. Moreover, although the isoelectric point of E. coli-rHuIFN-beta was pH 8.9, purified fibroblast HuIFN-beta exhibited multiple isoelectric points, probably due to heterogeneity of the carbohydrate moiety. These results indicate that the E. coli-rHuIFN-beta polypeptide folds similarly to fibroblast HuIFN-beta, and the carbohydrate moiety of natural HuIFN-beta has little influence on higher-order structure but does influence the hydrophobic and the electrostatic properties of the molecule.