[High level expression of human atrial natriuretic peptide in fusion form in E. coli system]

To construct recombinant plasmid with human atrial natriuretic peptide (ANP) gene in fusion form for stable and high level expression of genetic engineering product ANP in E. coli system.

Plasmids with ANP fusion gene were constructed by PCR and sub-cloning and fusion protein was expressed in E. coli system. High level expression of the fusion genes was enhanced by linking operons in tandem. ANP was released from the fusion protein with thrombin treatment and purified by chromatography. Genetic-engineered ANP was evaluated with the drug production requirement, and produced ANP was tested for its effects of lowering blood pressure and diuresis in vivo and vasodilation in vitro.

A series of 4 plasmid pCW111-114, containing 1 to 4 gene operons respectively, were constructed, and the yields of fusion protein were 46%, 54.8%, 56.1% and 60.1% of total cell protein. Fusion protein in the form of inclusion body was isolated and purified, and then treated with thrombin to release ANP. After purification using chromatography columns, at least 3 mg/L culture of ANP with the purity higher than 96% was produced in shaking flask. Primary pharmacological evaluation showed the produced ANP had the effects of blood pressure lowering in vivo and diuresis in vivo and vasodilation in vitro, which was similar to the activity of standard ANP.

By the protocol of fusion gene cloning and expression, the human ANP was produced successfully in E. coli system.