Abstract: Disclosed herein are novel compositions and methods for enhancing the solubility and promoting the adoption of native folding conformation of a protein or polypeptide expressed by recombinant DNA techniques. One embodiment of the present invention relates to a protein or polypeptide of interest is modified through either carboxyl- or amino-terminal peptide extension, so as to promote folding within host cells. Another embodiment relates to a method for enhancing the in vitro renaturation of a protein or polypeptide of interest expressed by recombinant DNA techniques, in circumstances where, following expression, a substantial percentage of the expressed protein or polypeptide of interest is localized within inclusion bodies.