Expression of a biologically active human granulocyte-macrophage colony stimulating factor fusion protein in Escherichia coli.

A gene encoding human granulocyte-macrophage colony stimulating factor(GM-CSF), was cloned into plasmid pEZZ318 and fused to a DNA segment coding for the signal peptide of staphylococcal protein A and a synthetic gene coding for a protein with ability to bind immunoglobulin G(IgG). The fusion protein was expressed in Escherichia coli and biologically actively secreted into the growth medium. Approximately all of the total activity was secreted into the culture medium, where levels of activity approached 1.96 x 10(8) units/liter. Purification of the fusion protein was performed in a single step by affinity chromatography with immobilized IgG to a specific activity of 1.2 x 10(8) units/mg.