Abstract: It is intended to provide techniques whereby a target protein is efficiently obtained as a normal protein even in the case of a protein which can be hardly expressed by usual recombinant DNA techniques. A fusion protein composed of a molecular chaperone, an intervening protein having an activity of cleaving a peptide bond, and a target protein is prepared, from which fusion protein the target protein is cleaved by the action of the intervening protein having the activity of cleaving a peptide bond. Examples of the intervening protein having the activity of cleaving a peptide bond include an intein and a protein consisting of a partial sequence of the intein.

Abstract: The present invention provides a chaperonin-target protein complex and a method of producing the same, and a method of stabilizing the target protein, a method of immobilizing the target protein, a method of analyzing the structure of the target protein, a sustained-release formulation, and a method of producing an antibody against the target protein. The chaperonin-target protein complex in the present invention includes a fusion protein having a chaperonin subunit and an affinity tag linked to the chaperonin subunit via a peptide bond and a target protein for which the affinity tag shows a specific affinity, wherein the target protein is bound to the affinity tag by means of the specific affinity, thereby forming a chaperonin ring structure consisting of a plurality of chaperonin subunits. The chaperonin-target protein in the present invention stabilizes the target protein and surely immobilize on a carrier without causing any change in its stereostructure.

Abstract: It is intended to provide an immunogen and a composition for immunological use by which a sufficient immune response is induced even by an antigen protein which has been considered unavailable to induce any effective immune responses for various reasons, and a method of producing an antibody using the same. The immunogen containing a fusion protein including the full-length or a part of a desired antigen protein and a folding factor or its subunit linked thereto via at least one peptide bond. Owing to the function of the folding factor, the antigen protein contained in the fusion protein is obtained as a soluble protein having a correct stereostructure. It is also possible to protect the antigen protein and from rapid decomposition in the blood of an animal having been inoculated therewith. The immunogen induces a higher immune response for an animal than an antigen protein alone. Examples of the folding factor include chaperonins and PPIases.