Expression of soluble, active human macrophage colony stimulating factor in Escherichia coli

Human macrophage colony stimulating factor (M-CSF) has been successfully overexpressed in Escherichia coli AD494 (DE3) with an expression level of approximate 26% of the total cellular proteins. The truncated human M-CSF gene encoding the amino-terminal 149 amino acids was subcloned into the prokaryotic expression vector pET11d under the control of the inducible T7 promoter. Nearly 40% of the recombinant protein was in the soluble fraction which showed obvious stimulating effects on mouse macrophage colony formation and had an M-CSF specific activity of approximately 1 x 10(6) units/mg soluble protein.