Expression of biologically active, mature human granulocyte-macrophage colony stimulating factor with an E. coli secretory expression system

Human granulocyte-macrophage colony stimulating factor (HuGM-CSF) was expressed periplasmically in Escherichia coli with the secretory vector, pINIIIompA2. HuGM-CSF protein thus expressed was shown to be faithfully cleaved and biologically active. This protein, however, could not be released by osmotic shock and, on subcellular fractionation, co-sedimented with the outer membrane fraction. The effect of promoters, vectors, host strains, induction conditions and media formulation on expression levels was also evaluated. Some of these factors play a significant role in determining maximal achievable levels of HuGM-CSF in the secretory expression system of E. coli .