Development of a protein-solubilizing expression method based on the synergistic action of intein ΔI-CM and the solubility enhancer elastin-like polypeptide

Abstract

Escherichia coli (E. coli) is often used as a host to produce a variety of recombinant proteins. However, the direct production of soluble and active protein containing disulfide bonds in E. coli remains a major challenge. In this study, we established a new, innovative soluble protein expression system based on the synergistic action of elastin-like polypeptide (ELP) and intein. Kinds of proteins including nanobodies, hIL-3 (Human Interleukin-3) analogue and AVN (the N terminal of A. ventricosus MiSp) with amino acid sequences that are normally express as insoluble form or difficult to express could be successfully expressed in soluble form in E. coli with this system. The soluble expression of the target proteins in the cytoplasm was achieved by the fusion of the solubility enhancer ELP, and the fusion of intein allowed the target proteins to be directly separated from the solubility enhancers in a mild enzyme-free environment. Through a one or two-step operation, nanobodies with high affinity activity, IL-3 analogue with bioactivity and soluble AVN were easily purified. This simple and efficient soluble expression system could thus be widely applied to facilitate the expression of difficult-to-express proteins.