Soluble Expression of Recombinant Nerve Growth Factor in Cytoplasm of Escherichia coli.

Abstract

Pivotal roles of Nerve growth factor (NGF) in the development and survival of both neuronal and non-neuronal cells indicate its potential for the treatment of neurodegenerative diseases. However, investigation of NGF deficits in different diseases requires the availability of properly folded human β-NGF. In previous studies bacterial expression of hNGF demonstrated the feasibility of its overproduction. However, known limitations in the use of E. coli as an expression host for a protein with three intra-chain disulfide bonds were evident. Here an optimized system was developed to overexpress the soluble NGF in E. coli. The gene encoding the β subunit of mature hNGF was optimized based on E. coli codon preference and cloned into pET-32a expression vector providing His- and Trx- tags for detection and increasing the solubility of recombinant protein, respectively. The recombinant DNA was expressed in E. coli Origami (DE3), which enhances the correct formation of disulfide bonds in the cytoplasm of E. coli. Different culture conditions were evaluated to increase soluble expression of the target protein. The highest soluble expression level was achieved when E. coli Origami (DE3) cells expressing NGF were grown at 30ºC in TB medium with 0.2 mM IPTG induction at OD600nm = 1 for 4 h. Our results indicated that the recombinant NGF was successfully expressed as a soluble form.