Fusion protein systems designed to increase soluble cytoplasmic expression of heterologous proteins in Escherichia coli
Harrison, R.G.; Davis, G.D.
Official Gazette of the United States Patent and Trademark Office Patents 1244(4)
A fusion sequence having a carrier protein which is preferably an E. coli protein having a predicted solubility probability of at least 90% fused to a target heterologous peptide or protein, and a host cell (especially E. coli) transformed with, or having integrated into its genome, a DNA sequence comprising a DNA encoding a carrier protein as defined herein fused to the DNA sequence of a selected heterologous peptide or protein. This fusion sequence is under the control of an expression control sequence capable of directing the expression of a fusion protein in the cell. An objective of the present invention is to improve the purification process of recombinant fusion proteins by avoiding the initial expression of these fusion proteins in E. coli as insoluble inclusion bodies. The methods and compositions of the present invention permit the production of large amounts of heterologous peptides or proteins in a stable, soluble form in certain host cells which normally express limited amounts of such soluble peptides or proteins. The present invention produces fusion proteins which retain the desirable characteristics of a carrier protein (i.e., stability, solubility, and a high level of expression).