Abstract: In a process for the production of a soluble native protein, such as immunoglobulin or methionine-prochymosin, in which an insoluble form of the protein is produced by a host organism transformed with a vector including a gene coding for the protein, the insoluble form of the protein is reversibly denatured in an alkaline aqueous solution at a pH selected to promote dissociation of a group or groups of the protein involved in maintaining the conformation of the protein, and the protein is subsequently allowed to renature by reducing the pH of the solution below a pH effective to denature the protein to produce the soluble native form of the protein. The pH of the alkaline aqueous is suitably in the range 9.0 to 11.5.

Abstract: The production of recombinant chymosin is disclosed in which an insoluble form of chymosin precursor is produced by a bacterial host cell transformed by a vector including a coding sequence for said precursor. Solubilization of said insoluble form of chymosin precursor is accomplished using urea at a concentration of at least 7M or guanidine hydrochloride at a concentration of at least 6M prior to cleaving said precursor to form chymosin. Said solubilization preferably additionally involves the denaturation of said precursor in an alkaline aqueous solution, e.g., at a pH between a 9 and 11.

Abstract: A process for the production of a fusion protein comprising an active portion of a chloramphenicol acetyltransferase (CAT) protein and a polypeptide. The fusion protein may be purified using CAT substrate affinity chromatography. The eucaryotic polypeptide may be calcitonin or a dervative thereof such as calcitonin-glycine. Other polypeptides described include enzymes such as chymosin, prochymosin and preprochymosin, hormones such as ACTH, insulins, and growth hormones and antigenic polypetides such as foot and mouth disease virus antigenic polypetide. The fusion protein may be cleaved at a site susceptible to selective enzymic or chemical cleavage to produce free polypeptide. The fusion protein may be used as an immunogen.