An Intrinsically Disordered Peptide Tag that Confers an Unusual Solubility to Aggregation-Prone Proteins
There is a high demand for the production of recombinant proteins in Escherichia coli for biotechnological applications but their production is still limited by their insolubility. Fusion tags have been successfully used to enhance the solubility of aggregation-prone proteins; however, smaller and more powerful tags are desired for increasing the yield and quality of target proteins. Herein, NEXT tag, a 53 amino acid-length solubility enhancer, is described. The NEXT tag showed outstanding ability to improve both in vivo and in vitro solubilities with minimal effect on passenger proteins. The C-terminal region of the tag was mostly responsible for in vitro solubility, while the N-terminal region was essential for in vivo soluble expression. The NEXT tag appeared to be intrinsically disordered and seemed to exclude neighboring molecules and prevent protein aggregation by acting as an entropic bristle. This novel peptide tag should have general use as a fusion partner to increase the yield and quality of difficult-to-express proteins.