[Isolation of recombinant interleukin-3 produced by E. coli]

A synthetic gene coding for human interleukin-3 (hIL3) was cloned in the plasmid pTE2IL3, the gene expression being controlled by the phage fd PVIII promotor and the phage T7 gene 10 translational enhancer. Under constitutive biosynthesis conditions in E. coli, the accumulation of recombinant hIL3 (in the inclusion bodies) was up to 30-40% of the total cell protein. An effective procedure of the hIL3 isolation is suggested. The hIL3 was solubilized in 5 M guanidinium chloride, renaturated and purified to homogeneity by a single chromatographic step. The protein's yield was 34 mg/g wet cells. The isolated hIL3 showed a specific biological activity.